How does an air purifier work in simple words?

A fan pulls room air into the purifier, pushes it through a pre-filter for large dust, a HEPA filter for fine particles and an activated carbon layer for some smells and gases, and then blows the cleaner air back out. In a closed room the same air is cleaned many times an hour, so the pollution level keeps falling.

Does a HEPA filter work like a sieve?

No. HEPA is a mat of fine fibres with gaps larger than many particles it catches. Big particles crash into fibres, mid-sized ones brush against them and stick, and the smallest drift randomly until they hit one. The hardest size to catch is around 0.1 to 0.3 microns, which is why HEPA grades are tested at that worst case.

What is CADR in an air purifier?

CADR, or Clean Air Delivery Rate, is how many cubic metres of clean air a purifier delivers each hour. It combines fan airflow and filter efficiency. Divide CADR by your room's volume to get air changes per hour. For Indian winters, four to five air changes an hour in a bedroom is a sensible target.

Do air purifiers need the windows closed?

Yes, while they run. A purifier cleans the air it can recirculate, so an open window keeps bringing in fresh pollution and the purifier never catches up. On good-air days, open windows to ventilate first, then close them and run the purifier. On smoggy days, keep doors and windows shut.

Does an air purifier add oxygen to the room?

No. An air purifier removes particles and, with activated carbon, some odours and gases. It does not create oxygen, remove carbon dioxide or remove carbon monoxide. If a closed room feels stuffy, it needs fresh outdoor air, which you get by opening a window when the outdoor air quality allows.

How does Auto mode on an air purifier work?

In Auto mode, a built-in particle sensor reads the air every few seconds. When PM2.5 or other readings rise, for example during cooking or when incense is lit, the fan speeds up. When the room is clean again, it slows down. This saves electricity and filter life compared with running on high all the time.

Can an air purifier remove viruses from the air?

A HEPA purifier can capture many of the droplets and aerosols that carry viruses, which lowers their airborne concentration in a closed room. It does not disinfect the room, clean surfaces or stop close-range spread between people. Use it as one small layer alongside ventilation, vaccination, hygiene and your doctor's advice, not instead of them.

Does a HEPA filter trap bacteria?

Most bacteria are around a micron or a few microns across, which is within the range a HEPA filter traps well. An H13 filter captures at least 99.95% of particles at its hardest size in a single pass. Only air that actually reaches the purifier is cleaned, so room size, CADR and keeping the room closed all matter.

Are air purifiers that kill 99.99% of germs real?

Such figures usually come from small sealed laboratory chambers, against one test organism, over a set time. Results in a furnished room with people moving about can be very different. Ask where, against what and over how long the claim was tested. Some ioniser and plasma features also produce ozone, which irritates the lungs.

What does an anti-bacterial coating on an air purifier filter do?

It limits the growth of bacteria on the filter media, where captured material collects over time. It does not sterilise the air in the room or kill germs on surfaces. Boon Airvana's filter has an anti-bacterial coating; its air cleaning comes from the H13 HEPA filter, and the filter should still be changed when the reminder says so.

Can an air purifier stop a cold or flu spreading at home?

No purifier can promise that. Colds and flu spread through close contact, droplets, surfaces and sometimes aerosols. A purifier only works on airborne particles that reach it. Giving the ill person their own room, ventilating, handwashing and following your doctor's advice matter more. See a doctor for high fever or breathing difficulty.

Is a UV air purifier better for germs than HEPA?

Not necessarily. UV inside a purifier only works on air while it passes the lamp, which may be a fraction of a second, and lab claims are often measured in small chambers. HEPA physically captures particles of the size that carry microbes. If a purifier has UV or an ioniser, make sure it does not produce ozone.

Category: Air Purifier

An air purifier is only as good as the air it actually moves through a real filter. Boon Airvana pairs an H13 HEPA filter (99.95% of particles in a single pass) and activated carbon with a CADR of 380 m³/h, enough for a room of about 484 sq ft, and more than nine air changes an hour in a 12 × 12 ft bedroom.

Its AtmoScan sensor reads PM1.0, PM2.5, PM10, TVOC, eCO₂, NO₂, temperature and humidity every second, so you see the number rather than a coloured ring. Auto mode follows the live AQI, Sleep runs quietly overnight, and the Boon app works with Alexa, Google Home and Matter.

Not sure what size you need? Use the air purifier size calculator, or read how to choose an air purifier for home. You can check your city’s air on the AQI by city page.

How Does an Air Purifier Work? Filters, Airflow and Sensors Explained
In This Guide

The Basic Idea: Fan Plus Filters

Stage 1: The Pre-Filter

Stage 2: How HEPA Catches Fine Particles

Stage 3: Activated Carbon for Smells and Gases

What CADR Measures

Sensors, Auto Mode and Why the Room Must Be Closed

What an Air Purifier Does Not Do

A Worked Example: Boon Airvana

Frequently Asked Questions
An air purifier works by pulling room air through a series of filters with a fan and blowing the cleaned air back out. A pre-filter stops hair and large dust, a HEPA filter traps fine particles such as PM2.5, and activated carbon adsorbs some odours and gases. Run it in a closed room and the same air passes through again and again, so the particle level falls with every cycle.

The Basic Idea: Fan Plus Filters

There is no chemistry trick at the heart of a good purifier. It is a fan and a stack of filters in a sealed box. The fan creates suction, room air is drawn in through the intake, it passes each filter layer in turn, and the outlet returns it to the room. Here is the path a parcel of air takes:
1. Intake: the fan draws room air in through the grille.
2. Pre-filter: a mesh catches hair, lint and visible dust.
3. HEPA filter: dense, pleated fibre media traps fine and very fine particles.
4. Activated carbon: a porous layer holds on to some odour and gas molecules.
5. Outlet: cleaner air leaves the top or front and mixes back into the room.
6. Repeat: that air is drawn in again, many times an hour.
The order matters. Coarse layers go first so they protect the finer, costlier ones from clogging early. Sealing matters too: any air that leaks around the edge of a filter skips it entirely.

Stage 1: The Pre-Filter

The pre-filter is a simple mesh. It catches what you can see: pet hair, human hair, fluff from clothes and the grey dust that settles on shelves. On its own it does almost nothing for PM2.5, but it keeps the HEPA layer from filling up with large debris. In dusty Indian homes it is the part that needs the most frequent attention; most pre-filters can be vacuumed or washed. Clean it whenever it looks grey or the purifier reminds you.

Stage 2: How HEPA Catches Fine Particles

HEPA is not a sieve with tiny holes. It is a mat of fine fibres laid in random directions, with gaps much larger than many of the particles it stops. Particles are caught in three ways, all ordinary physics:
- Impaction: larger, heavier particles cannot follow the air as it bends around a fibre, so they crash into it and stick.
- Interception: mid-sized particles follow the airflow but pass close enough to a fibre to touch it and stay attached.
- Diffusion: the smallest particles are knocked about by air molecules and wander in a zigzag, which makes them very likely to hit a fibre.
Big particles are caught well by impaction and the tiniest by diffusion. The hardest size sits in between, roughly around 0.1 to 0.3 microns, where neither effect is strong. That is why HEPA grades are tested at the most penetrating particle size: the rating is a worst case, and particles larger or smaller are captured even more easily. An H13 filter captures at least 99.95% of particles at that size in a single pass. For how grades compare, see the HEPA vs ioniser vs UV comparison.

Stage 3: Activated Carbon for Smells and Gases

Gas molecules are far too small for HEPA to hold. Activated carbon works differently: it is charcoal treated to be full of microscopic pores, which gives it a very large internal surface. Some gas and odour molecules stick to that surface, a process called adsorption. It helps with cooking smells, some volatile organic compounds and stale odours. It fills up over time, and it is not a fix for every gas.

In one line: the pre-filter protects, HEPA catches particles, carbon holds some gases, and the fan decides how fast all of that happens.

What CADR Measures

Clean Air Delivery Rate (CADR) is the volume of particle-free air a purifier delivers per hour, in m³/h. It combines two things: how much air the fan moves, and how much of the pollution the filter removes from that air. A purifier with a superb filter but a weak fan has a low CADR; so does a strong fan pushing air through a leaky or poor filter.

CADR is what turns a box into a result. Divide it by your room’s volume and you get air changes per hour (ACH), the number of times the room’s air passes through the filter each hour. For Indian winters, four to five ACH in a bedroom is a good aim. The air purifier size guide explains the arithmetic, and the calculator does it for you.

Enter your room’s length, width and ceiling height to see the CADR it needs.
Size Your Room →

Sensors, Auto Mode and Why the Room Must Be Closed

Many purifiers carry an air-quality sensor. A laser particle sensor shines light through a small air sample and counts the flashes scattered by particles, sorting them by size into readings such as PM1.0, PM2.5 and PM10. In Auto mode, the purifier reads this every few seconds and speeds the fan up when the number rises (cooking, incense, a door opened to smog) and slows down once the room is clean. Sensors measure particle size, not what particles are, so no home sensor can tell pollen from dust.

The room should be closed because a purifier only cleans the air it can recirculate. With a window open, outdoor air keeps arriving and the machine ends up cleaning the street. On good-air days, ventilate first and then close up; on bad-air days, keep doors and windows shut while it runs. The where to place an air purifier in an Indian home guide covers fans and ACs.

What an Air Purifier Does Not Do
- It does not remove carbon monoxide. Neither HEPA nor carbon deals with it. A CO alarm and proper ventilation of any combustion source are what protect you.
- It does not add oxygen. It cleans the air already in the room. A stuffy room needs fresh outdoor air.
- It does not change humidity. That is a humidifier’s or dehumidifier’s job.
- It does not clean surfaces. Dust that has already settled on the floor and sofa needs a cloth and a vacuum.
Our guide on what air purifiers cannot remove goes into each limit in more detail.

A Worked Example: Boon Airvana

Boon Airvana follows the same principles, with a few design choices worth explaining:
- Dual suction: air is drawn in from both sides, through two filters, rather than through one intake.
- Four stages: a washable pre-filter mesh, H13 HEPA (99.95% of particles in a single pass), activated carbon for gases and odours, and an anti-bacterial coating on the filter.
- CADR 380 m³/h: about 484 sq ft at a 3 m ceiling at roughly 2.8 air changes an hour, and more than nine air changes an hour in a 12 × 12 ft bedroom.
- AtmoScan sensor: PM1.0, PM2.5 and PM10 (laser-based), plus TVOC, estimated CO₂, NO₂, temperature and humidity, read every second. Auto mode follows the real-time AQI.
Its fresh-air alert is a good illustration of the limits above: when estimated CO₂ rises, the purifier cannot fix it, so it tells you the room needs outdoor air. Airvana is ₹14,900 at the time of writing.

Frequently Asked Questions

How does an air purifier work in simple words?

A fan pulls room air into the purifier, pushes it through a pre-filter for large dust, a HEPA filter for fine particles and an activated carbon layer for some smells and gases, and then blows the cleaner air back out. In a closed room the same air is cleaned many times an hour, so the pollution level keeps falling.

Does a HEPA filter work like a sieve?

No. HEPA is a mat of fine fibres with gaps larger than many particles it catches. Big particles crash into fibres, mid-sized ones brush against them and stick, and the smallest drift randomly until they hit one. The hardest size to catch is around 0.1 to 0.3 microns, which is why HEPA grades are tested at that worst case.

What is CADR in an air purifier?

CADR, or Clean Air Delivery Rate, is how many cubic metres of clean air a purifier delivers each hour. It combines fan airflow and filter efficiency. Divide CADR by your room’s volume to get air changes per hour. For Indian winters, four to five air changes an hour in a bedroom is a sensible target.

Do air purifiers need the windows closed?

Yes, while they run. A purifier cleans the air it can recirculate, so an open window keeps bringing in fresh pollution and the purifier never catches up. On good-air days, open windows to ventilate first, then close them and run the purifier. On smoggy days, keep doors and windows shut.

Does an air purifier add oxygen to the room?

No. An air purifier removes particles and, with activated carbon, some odours and gases. It does not create oxygen, remove carbon dioxide or remove carbon monoxide. If a closed room feels stuffy, it needs fresh outdoor air, which you get by opening a window when the outdoor air quality allows.

How does Auto mode on an air purifier work?

In Auto mode, a built-in particle sensor reads the air every few seconds. When PM2.5 or other readings rise, for example during cooking or when incense is lit, the fan speeds up. When the room is clean again, it slows down. This saves electricity and filter life compared with running on high all the time.

See how Boon Airvana’s dual-suction, four-stage design and eight-parameter sensor come together, ₹14,900 at the time of writing.
See Boon Airvana →
October 19, 2026

Musty Smell and Monsoon Mould: Fixing the Cause, Not the Symptom

A musty smell in the house during monsoon means mould or bacteria are actively growing somewhere, usually on a cool external wall, behind furniture or inside a wardrobe. The fix is moisture: find the leak or condensation, get air moving and bring the humidity down. Cleaning, air fresheners and air purifiers deal with symptoms; they do not stop the growth.

What that smell is

The typical musty smell of monsoon is not “damp” in the abstract. It is a set of volatile compounds released by mould and bacteria as they actively grow and feed.

That matters more than it sounds, because it makes the smell diagnostic: if you can smell it, something is growing right now. It is not left over from a previous wet spell, and it will not fade on its own while the conditions that produce it continue.

The core principle: mould is a moisture problem dressed up as a biology problem. Every effective fix is about water. Everything aimed at the mould itself is maintenance.

Where it is growing

Often not where you can see it. Common sites in Indian homes:

External walls, especially north-facing and shaded ones, where the wall stays cool and moisture condenses on it
Behind and beneath furniture pushed flush against an external wall, with no air movement and no drying
Inside wardrobes and cupboards, particularly those on an external wall, where still, enclosed air holds moisture
Bathroom ceilings and grout, and any bathroom without a working exhaust fan
Under sinks, around slow leaks that never get noticed
Window frames and sills, where condensation runs down and collects
Mattresses and upholstery in a room that stays humid

If a room smells musty and nothing is visible, move the furniture away from the external wall and look behind it. That is the most common answer.

Why cleaning it off does not work

Wiping growth off a wall removes what you can see. It does not remove the water that allowed it, and the water is the reason it was there.

The moisture usually comes from one of four sources, and identifying which one matters because the fixes are entirely different:

Source	Tell	Fix
Leak (plumbing or roof)	Localised patch, often worse after rain	Repair it. Nothing else works
Rising damp	Low on the wall, often with a tide line	Structural; needs a professional
Condensation	Cold external walls, window frames, worse in enclosed corners	Ventilation, air movement, lower indoor humidity
Ambient humidity	Whole room smells; nothing visibly wet	Dehumidify and ventilate

Fixing the cause

Find the water. Check for leaks first: under sinks, around the bathroom, at the ceiling. A leak makes everything else pointless.
Get air moving. Still air is what lets moisture sit on a surface long enough for growth. Pull furniture a few inches off external walls, and leave wardrobe doors ajar during the day.
Ventilate at the right time. During monsoon, outdoor air is often more humid than indoor air, so opening up on a wet day can make things worse. Open windows on drier, brighter days, and use fans for air movement inside otherwise.
Use exhaust fans properly. Run the bathroom fan during a shower and for fifteen minutes after. Run the kitchen chimney throughout cooking. Both rooms are humidity sources.
Dehumidify where practical. Mould growth slows markedly once indoor humidity comes down, and a dehumidifier is the appliance that does that job. A humidity reading, from a hygrometer or a purifier with a humidity sensor, tells you whether it is working.
Then clean the growth. Hard surfaces can be cleaned. Porous items that are thoroughly grown through, such as a mattress or some upholstery, often cannot be saved.

The same problem with smoke odour

Cigarette smoke smell in a room follows exactly the same logic, which is why it belongs here.

Smoke residue is not floating in the air weeks later. It has bound into soft materials and settled as a fine film on walls and ceilings. Filtering the air removes what is currently suspended and leaves the reservoir untouched, which is why a room can smell clean for an hour and then smell of smoke again.

What works: wash every textile that can be washed; wipe hard surfaces, including the ceiling, which is usually skipped and holds a great deal; ventilate steadily over days rather than hours; and in persistent cases, repaint with a sealing primer that locks the residue into the wall.

When mould is a health issue

For most people, mould exposure is an irritant: cough, blocked nose and itchy eyes that improve on leaving the building.

It matters more for some households:

Asthma and allergy. Mould is a well-recognised trigger and can noticeably worsen control.
Infants and elderly people. They are more susceptible to respiratory irritation.
Anyone immunocompromised. They should get specific medical advice rather than general reassurance.

If symptoms consistently improve when someone is away from the house and return within a day of coming back, take that pattern to a doctor, and see one promptly for any wheezing, breathlessness or a cough that lasts more than a couple of weeks. Then deal with the mould properly rather than seasonally. Our guide to a constant cough at home covers other indoor causes worth ruling out.

Preventing next monsoon

Repair leaks before the rains, not during them
Keep furniture off external walls permanently; a few inches is enough
Fit or fix the bathroom exhaust fan, since the bathroom is the largest humidity source in most homes
Dry laundry outdoors or in a ventilated space, because drying clothes in a closed room adds a lot of water to the air
Check wardrobes on external walls at the start and end of the season
Consider anti-fungal paint on walls where mould keeps returning. It buys time, though it does not replace fixing the moisture

Where an air purifier helps, and where it does not

An air purifier is not a mould fix, and it is worth being clear about that before anything else. It does not dry a wall, does not lower humidity and does not stop growth that is already happening. If a purifier is masking a musty smell, something in the room is still wet. Our guide to what air purifiers cannot remove covers the other limits.

What it can do, once the moisture is under control, is reduce what is already in the air. A HEPA filter captures airborne particles, which include mould spores, and an activated carbon stage helps with odours. For someone with asthma or an allergy, cleaner bedroom air while the house dries out can be worth having, alongside, not instead of, medical advice.

Boon Airvana pairs an H13 HEPA filter (99.95% of particles in a single pass) with activated carbon for odours, and its AtmoScan sensor reads humidity alongside PM2.5 and PM10 every second. It will not dry a damp wall, but it shows you whether the room is improving.

See Boon Airvana →

A few practical notes if you do use one. Size it for the room, because an undersized purifier is the most common reason people are disappointed: our air purifier size calculator works out the CADR a room needs. Place it where air can reach it from both sides, not pushed against the damp wall; see where to place an air purifier. And remember that particle sensors measure particle size, not what the particles are, so no purifier can tell you that the particles it sees are mould spores.

Frequently Asked Questions

How do I get rid of a musty smell in my house during monsoon?

Find and stop the moisture, because the smell is a by-product of mould that is actively growing. Improve ventilation and air movement in the affected room, dry out whatever is damp, and clean visible growth off hard surfaces. Air fresheners and filtration hide or reduce the smell without dealing with what is producing it.

Why does mould keep coming back on my walls?

Because the moisture that allows it is still there. Wiping growth off a surface removes what you can see while the damp remains, whether it comes from a leak, rising damp, condensation on a cold external wall or persistently high humidity, so the growth simply returns. Cleaning is maintenance; the fix is drying the wall out and keeping it dry.

Is monsoon mould dangerous to health?

For most people it is an irritant, causing cough, a blocked nose and itchy eyes that are worse indoors. For anyone with asthma or an allergy it can be a significant trigger, and people who are immunocompromised should get medical advice. Extensive growth in a home someone is living in should be dealt with rather than tolerated.

Does an air purifier remove mould smell?

It reduces airborne spores, and an activated carbon stage will reduce some of the odour compounds. Neither stops the growth. If a purifier is masking a musty smell, something in the room is still wet and still growing, so treat the smell as a signal to find the moisture rather than something to filter away.

How do I get cigarette smoke smell out of a room?

The same way as mould odour: deal with the reservoir rather than the air. Smoke residue binds into soft materials and settles as a film on walls and ceilings, so you need to wash textiles, wipe hard surfaces including the ceiling, ventilate steadily over several days, and in persistent cases repaint with a sealing primer.

Once the damp is fixed, Boon Airvana keeps the air in the room clean and shows humidity, PM2.5 and PM10 live, so you can see the room recover. ₹14,900 at the time of writing.

See Boon Airvana →

October 19, 2026

Do Air Purifiers Remove Viruses and Bacteria? An Honest Answer
In This Guide

The Short Answer

Germs, Droplets and What HEPA Can Catch

Filtration Is Not Disinfection

Reading Kills 99.99% Claims

What an Anti-Bacterial Filter Coating Does

What Actually Lowers Infection Risk at Home

Frequently Asked Questions
A HEPA air purifier can capture many airborne bacteria and the droplets and aerosols that carry viruses, so it can lower how much of them is floating in a closed room. That is not the same as disinfecting the room or preventing infection. Treat a purifier as one small layer alongside ventilation, vaccination, hygiene and your doctor’s advice, never as a replacement for them.

The Short Answer

Whether a purifier “removes germs” depends on what you mean. If you mean “captures some airborne microbes and lowers their concentration in the room’s air”, a correctly sized HEPA purifier in a closed room does that. If you mean “kills germs on surfaces”, “stops a family member’s cold spreading” or “makes the room sterile”, no home purifier does that, whatever the box says.

Infections spread in many ways: close face-to-face contact, larger droplets that fall within a short distance, touching contaminated surfaces, and, for some illnesses, smaller aerosols that linger. A purifier works only on the last part, and only on the air that actually passes through it.

Germs, Droplets and What HEPA Can Catch

Most bacteria are around a micron or a few microns across, comfortably within the range a HEPA filter traps. Individual viruses are much smaller, but they rarely travel through the air on their own. They ride inside droplets and aerosols of breath, saliva and mucus, which are larger.

HEPA filters are rated at their hardest particle size, roughly 0.1 to 0.3 microns, and capture particles both larger and smaller than that even more efficiently. So, in principle, the particles that carry microbes are the kind HEPA handles well. An H13 filter captures at least 99.95% of particles at that worst-case size in a single pass. A clogged or overdue filter does this less well, so air purifier maintenance and filter care matters too.

The catch is not the filter; it is the room. Only air that reaches the purifier gets cleaned. Someone coughing a metre away from you shares their breath with you long before it drifts to the purifier across the room.

The honest framing: a HEPA purifier can reduce airborne particles that may carry germs. It does not disinfect a room, kill germs on surfaces, or replace ventilation, vaccination or medical care.

Filtration Is Not Disinfection

Disinfection means killing or inactivating microbes. Filtration means moving them from the air onto a filter. A HEPA purifier does the second. The difference matters in three ways:
- Surfaces are untouched. Door handles, phones, taps and shared towels are a common route for many infections. Cleaning and handwashing handle those.
- Ventilation still matters. Opening windows when the outdoor air allows replaces stale indoor air entirely. A purifier recirculates the same air; it does not bring in fresh air or lower CO₂.
- Speed is limited by CADR. In a 12 × 12 ft room with enough CADR for five air changes an hour, room air passes through the filter about five times an hour. That helps, but it is not instant, and it cannot outpace someone sneezing at close range.
For the wider picture of where purifiers help and where they do not, see whether air purifiers actually work.

Reading Kills 99.99% Claims

Listings for purifiers with UV lamps, ionisers, “plasma” or photocatalytic stages often promise to kill 99.9% or 99.99% of viruses and bacteria. Before you trust the number, ask how it was measured:
1. Where was it tested? Most such figures come from a small sealed laboratory chamber, not a furnished room with people walking in and out.
2. Against what? One test organism under set conditions does not cover every virus or bacterium.
3. Over what time? A reduction measured over an hour or more in a tiny chamber can sound instant on a box.
4. Compared with what? Some claims include the microbes that would have settled or died naturally in the chamber anyway.
UV inside a purifier also has a basic limit: air rushes past the lamp in a fraction of a second, which may be too brief to inactivate much. Some ionisers and plasma features produce ozone, a lung irritant. The HEPA vs ioniser vs UV comparison explains why HEPA is the safer core technology.

Boon Airvana is built around an H13 HEPA filter, a washable pre-filter and activated carbon, with no claim to sterilise your room. ₹14,900 at the time of writing.
See Boon Airvana →

What an Anti-Bacterial Filter Coating Does

Some filters, including Boon Airvana’s, carry an anti-bacterial coating. It is worth being precise about what that means. The coating is on the filter, and its job is to limit the growth of bacteria on the filter media itself, where captured material collects over weeks of use. It does not sterilise the air in your room, it does not kill germs on your surfaces, and it is not a reason to delay changing the filter when the purifier says it is due.

Put simply: the HEPA layer captures particles; the coating helps keep the filter cleaner while it holds them. Neither turns a purifier into a disinfection device.

What Actually Lowers Infection Risk at Home
- Follow your doctor’s and health authorities’ guidance on vaccination, isolation when ill and masks. Infection control is a medical question, not an appliance question.
- Ventilate when the outdoor air allows, especially when someone at home is unwell. Check your city’s air on the AQI by city page first.
- Wash hands and clean shared surfaces regularly.
- Give an ill person their own room where possible. A purifier in that room can lower airborne particle levels, as one layer among these.
See a doctor if anyone has a high or persistent fever, difficulty breathing, chest pain, confusion, or symptoms that worsen after a few days. Seek care promptly for infants, older family members and anyone with a long-term heart or lung condition.

Frequently Asked Questions

Can an air purifier remove viruses from the air?

A HEPA purifier can capture many of the droplets and aerosols that carry viruses, which lowers their airborne concentration in a closed room. It does not disinfect the room, clean surfaces or stop close-range spread between people. Use it as one small layer alongside ventilation, vaccination, hygiene and your doctor’s advice, not instead of them.

Does a HEPA filter trap bacteria?

Most bacteria are around a micron or a few microns across, which is within the range a HEPA filter traps well. An H13 filter captures at least 99.95% of particles at its hardest size in a single pass. Only air that actually reaches the purifier is cleaned, so room size, CADR and keeping the room closed all matter.

Are air purifiers that kill 99.99% of germs real?

Such figures usually come from small sealed laboratory chambers, against one test organism, over a set time. Results in a furnished room with people moving about can be very different. Ask where, against what and over how long the claim was tested. Some ioniser and plasma features also produce ozone, which irritates the lungs.

What does an anti-bacterial coating on an air purifier filter do?

It limits the growth of bacteria on the filter media, where captured material collects over time. It does not sterilise the air in the room or kill germs on surfaces. Boon Airvana’s filter has an anti-bacterial coating; its air cleaning comes from the H13 HEPA filter, and the filter should still be changed when the reminder says so.

Can an air purifier stop a cold or flu spreading at home?

No purifier can promise that. Colds and flu spread through close contact, droplets, surfaces and sometimes aerosols. A purifier only works on airborne particles that reach it. Giving the ill person their own room, ventilating, handwashing and following your doctor’s advice matter more. See a doctor for high fever or breathing difficulty.

Is a UV air purifier better for germs than HEPA?

Not necessarily. UV inside a purifier only works on air while it passes the lamp, which may be a fraction of a second, and lab claims are often measured in small chambers. HEPA physically captures particles of the size that carry microbes. If a purifier has UV or an ioniser, make sure it does not produce ozone.

Boon Airvana: H13 HEPA, activated carbon and an eight-parameter sensor, sold for what filtration really does. ₹14,900 at the time of writing.
See Boon Airvana →
October 19, 2026

Anti-Mosquito Air Purifier: Does It Work? A Myth-Check for Indian Homes

An air purifier does not repel or kill mosquitoes. Its fan and filters are built to catch microscopic particles, and a mosquito is neither drawn to it nor harmed by it. What protects a bedroom is nets, window screens, removing standing water and repellents used as directed. A purifier’s real role is smaller: it can help clear the smoke that mosquito coils leave behind.

The Short Answer

Searches for an “anti mosquito air purifier” usually blend two different products. One is a regular air purifier, which cleans particles from the air. The other is a mosquito trap or “mosquito killer” machine, which uses light and a fan to lure and catch insects. They look similar on a shelf and are sometimes sold together, but they do different jobs, and neither replaces the basics.

Device	What it does	Effect on mosquitoes	Effect on indoor air
HEPA air purifier	Filters fine particles, some odours and gases	None	Lowers particles, including coil smoke
UV or fan mosquito trap	Lures insects with light, catches them with a fan or grid	Mixed; varies by species and setting	None
Coil or incense-style repellent	Burns to release repellent with smoke	Repels while burning	Adds smoke and fine particles
Liquid or mat vaporiser	Heats a repellent so it spreads into the room	Repels while running	Adds repellent vapour to the air
Net and window screens	Physical barrier	Keeps them off you	None

Why an Air Purifier Cannot Stop Mosquitoes

A purifier’s fan draws air gently into its intake, and the pre-filter and HEPA layers are designed for dust, smoke and fine particles. A mosquito is a strong, deliberate flier that is attracted to people by the carbon dioxide we breathe out, body warmth and skin odours. A purifier offers none of those cues, and its intake is not designed to pull in and trap a flying insect.

If a product calls itself an air purifier and claims to kill mosquitoes, check which part does the killing. Usually it is a separate light-and-grid or trap feature bolted on, and the air-cleaning part is unrelated. For how a purifier works and what it can remove, see whether air purifiers actually work.

UV and Fan Mosquito Traps Are a Different Device

Mosquito traps and “mosquito killer” lamps use ultraviolet or blue light to attract insects, then catch them with a fan, sticky board or electric grid. They do catch insects, but the evidence that they meaningfully reduce bites is mixed. Many of the insects they catch are not the biting kinds, and the mosquitoes that matter most for dengue tend to bite by day and respond to human cues more than to light. Treat them as an extra, not as your main protection, and never as a reason to skip the net.

The plain truth: no air purifier keeps mosquitoes away. Nets, screens and removing standing water do. A purifier only helps with the smoke some repellents leave behind.

Coils, Vaporisers and Your Indoor Air

Mosquito coils work by smouldering, and like agarbatti and dhoop, that slow burn releases smoke made of fine particles, along with gases. In a closed bedroom, a coil burning all night can push indoor PM2.5 well up while you sleep beside it. The same physics applies to incense; our guide on agarbatti and dhoop smoke indoors explains what that smoke contains and how to reduce it.

Liquid and mat vaporisers do not burn, so they produce far less smoke, but they do release repellent into the room’s air on purpose. That is how they work. Use any repellent product exactly as the label directs: keep the room ventilated where the label says so, keep products away from infants and pets as instructed, and do not run several at once in a small closed room.

If anyone at home has asthma or a persistent cough, smoke-producing repellents are worth avoiding altogether; see constant cough at home and talk to your doctor.

What Actually Keeps Mosquitoes Out

Sleep under a mosquito net, especially for babies, young children and anyone unwell.
Fit mesh screens on windows, ventilators and balcony doors, and keep doors shut at dusk.
Remove standing water every week: coolers, flower-pot saucers, buckets, old tyres, overhead tank lids and the tray under the fridge. Many household mosquitoes breed in clean, still water close to the home.
Use repellents as directed on exposed skin when you are outdoors or awake indoors at biting times, following the label for children.
Wear long sleeves and trousers at dawn and dusk, and through the day in dengue season.
Support your building’s or society’s fogging and clean-up drives, since mosquitoes breed beyond your own walls.

Dengue and Malaria: When to See a Doctor

Mosquito season in India brings dengue, malaria and chikungunya. See a doctor promptly for any fever during mosquito season, rather than waiting it out. Seek care urgently for warning signs such as severe abdominal pain, repeated vomiting, bleeding from the gums or nose, blood in vomit or stools, unusual drowsiness or restlessness, difficulty breathing, or fever with chills and shivering. Children, older adults and pregnant women need earlier attention. Do not self-medicate for fever in this season without medical advice; follow your doctor’s guidance on tests and treatment.

Where a Purifier Does Help

If you use coils or other smoke-producing repellents, a HEPA purifier can bring down the fine particles they leave in the room, and an activated carbon layer can help with some of the smell. The better move is to switch to a net or screens and drop the coil, but where that is not possible, a purifier limits the smoke. It is also useful after Diwali and other smoky evenings; see Diwali smoke and indoor air.

Boon Airvana’s AtmoScan sensor reads PM1.0, PM2.5 and PM10, so you can watch the reading rise when a coil is lit and fall once it is out and the purifier runs. It will not keep a single mosquito out of the room. It is ₹14,900 at the time of writing.

Frequently Asked Questions

Does an anti mosquito air purifier work?

An air purifier does not repel or kill mosquitoes. Products sold as anti mosquito purifiers usually combine a normal air filter with a separate light trap, and the evidence that such traps meaningfully reduce bites is mixed. Mosquito nets, window screens, removing standing water and repellents used as directed are what actually protect you.

Can an air purifier catch mosquitoes?

No. An air purifier’s intake draws air gently and its filters are designed for dust, smoke and fine particles, not flying insects. Mosquitoes are attracted to the carbon dioxide we breathe out, body warmth and skin odours, which a purifier does not provide. It will not trap or kill them in any useful number.

Is mosquito coil smoke harmful indoors?

Mosquito coils smoulder and release smoke containing fine particles and gases, much like agarbatti. In a closed bedroom overnight, that can raise indoor PM2.5 while you sleep. A net or window screens avoid the smoke entirely. If anyone at home has asthma or a persistent cough, avoid smoke-producing repellents and talk to your doctor.

Can I run an air purifier while a mosquito vaporiser is on?

Yes. A vaporiser releases repellent into the air on purpose, and a purifier with activated carbon may capture some of it, which could make the vaporiser less effective. Follow the vaporiser’s label for ventilation and room size. For bedrooms, a mosquito net with the purifier running is the cleaner combination.

Do mosquito killer machines work?

Light-based mosquito traps and killer lamps do catch insects, but many catches are not biting species, and the mosquitoes that spread dengue tend to bite by day and respond to human cues more than light. Treat them as an extra rather than your main protection. Nets, screens and removing standing water matter more.

When should I see a doctor for fever in mosquito season?

See a doctor promptly for any fever during mosquito season. Go urgently for severe abdominal pain, repeated vomiting, bleeding from the gums or nose, blood in vomit or stools, unusual drowsiness, breathing difficulty, or fever with chills. Children, older adults and pregnant women need earlier attention. Do not self-medicate without medical advice.

Already using coils? Boon Airvana’s H13 HEPA filter and live PM readings help clear the smoke, while your net keeps the mosquitoes out.

See Boon Airvana →

October 19, 2026

PM2.5 vs PM10: What Is the Difference and Which Matters More Indoors?

PM10 is particulate matter 10 microns across or smaller; PM2.5 is the finer fraction, 2.5 microns or smaller. PM10 is mostly dust and mostly lodges in the nose and throat, while PM2.5 is mostly smoke and combustion particles and can travel deep into the lungs. Indoors, PM2.5 is the number that matters more, and a HEPA purifier captures both.

What the Numbers Mean

“PM” stands for particulate matter: tiny solid or liquid particles floating in air. The number is a size cut-off in microns (a micron is a thousandth of a millimetre).

PM10 includes every particle 10 microns or smaller.
PM2.5 includes every particle 2.5 microns or smaller.
PM1.0 includes every particle 1 micron or smaller.

These are nested, not separate. All of PM2.5 is also counted inside PM10, and all of PM1.0 is inside PM2.5. So when a monitor shows PM10 higher than PM2.5, that is expected: the PM10 figure includes the fine particles plus the coarser ones between 2.5 and 10 microns. Both are far too small to see individually; a human hair is many times wider than either.

Where Each Comes From in Indian Cities

	Coarser particles (PM10 side)	Fine particles (PM2.5 side)
Main outdoor sources	Road dust, construction and demolition, unpaved ground, wind-blown soil	Vehicle exhaust, stubble and crop-residue burning, wood and waste burning, industry, firecrackers
Main indoor sources	Sweeping, dusting, shaking bedding, fans lifting settled dust	Frying and tadka, agarbatti and dhoop, mosquito coils, smoking, candles
How they behave	Settle out of the air relatively quickly; come back up when disturbed	Stay suspended for a long time; travel far and slip through gaps
When they peak	Dry, windy days; near construction; summer dust	Still, cold evenings and nights; October to January in north India

This is why a dusty house in summer and a smoky winter evening feel different. Dust you can often see on surfaces; our guide on why your house gets so dusty covers that side. Winter smog is mostly the fine fraction, which you cannot see settling anywhere.

Why PM2.5 Does More Harm

The body’s airways act like a series of filters. Larger particles are mostly caught in the nose and throat and cleared by mucus, sneezing and coughing. The smaller the particle, the further it gets:

Coarse particles in PM10 mostly irritate the nose, throat and upper airways. That is the sneezing, itchy throat and dust-allergy side of air pollution.
PM2.5 can reach the small airways and air sacs deep in the lungs, where the body’s clearing mechanisms are slower.
Fine particles from combustion also tend to carry the products of burning with them, which is part of why smoke is treated as more harmful than plain dust.

That is why the health limits for PM2.5 are much stricter than for PM10, and why public health agencies focus on PM2.5. If smog season brings on throat burning or watery eyes, see our page on throat irritation and burning eyes in smog; for anything that persists or affects breathing, see a doctor.

In one line: PM10 is mostly the dust you can sweep; PM2.5 is mostly the smoke you cannot see. Indoors in winter, watch PM2.5 first.

PM1.0: The Smallest Number on Your Monitor

Some monitors and purifiers also report PM1.0. It is the finest slice of PM2.5 and is dominated by fresh combustion particles: vehicle exhaust, burning, incense and cooking smoke. There is no Indian standard for PM1.0, so it is best used as a trend signal. If PM1.0 jumps while you are cooking or lighting dhoop, the source is in the room; if it climbs slowly in the evening with the windows shut, it is likely seeping in from outside.

What Each Kind of Sensor Can See

Most home air-quality monitors and purifier sensors use a laser particle sensor. A small fan draws air past a laser beam, the sensor counts the flashes of scattered light, and software estimates the mass in each size range.

Laser particle sensors report PM1.0, PM2.5 and PM10. They measure particle size, not what the particle is. They cannot tell pollen from smoke from dust.
Gas sensors (TVOC, eCO₂, NO₂) measure different things altogether: volatile chemicals, an estimate of carbon dioxide build-up, and a traffic-related gas. They do not see particles.
Older or very cheap “dust” sensors often report a single vague number and struggle with the finest particles. A monitor that shows only one unlabelled number is not telling you much.

For a full comparison of monitors, apps and what each can measure, read how to check air quality at home.

Boon Airvana’s AtmoScan sensor reads PM1.0, PM2.5 and PM10 with a laser, plus TVOC, eCO₂ and NO₂, every second, so you can see which kind of pollution is in your room.

See Boon Airvana →

How a HEPA Purifier Handles Both

A HEPA filter is a dense mat of fine fibres. It does not work like a sieve with holes of a fixed size; particles are caught by several mechanisms at once. Large particles slam into fibres, mid-sized ones are intercepted as they pass close to a fibre, and the very smallest ones zig-zag randomly and stick when they touch a fibre. There is a size in between, around 0.3 microns, that is hardest to catch, and HEPA filters are rated at that hardest size.

PM10: the pre-filter catches the largest dust and hair; the HEPA layer catches the rest of the coarse fraction easily.
PM2.5 and PM1.0: captured by the HEPA layer. An H13 grade filter captures 99.95% of particles in a single pass at its rated test size.
Gases and smells: not captured by HEPA at all. That is the job of an activated carbon layer, and even carbon only helps with some gases. Our guide on HEPA vs ionizer vs UV purifiers explains why HEPA is the technology to rely on for particles.

The filter grade is only half the story. How much air passes through the filter each hour (the CADR) decides how quickly the room’s particle level actually falls.

Indian Limits and Which Number to Watch

Standard	PM2.5	PM10
India NAAQS, 24-hour	60 µg/m³	100 µg/m³
India NAAQS, annual	40 µg/m³	60 µg/m³
WHO 2021 guideline, 24-hour	15 µg/m³	Not covered here
WHO 2021 guideline, annual	5 µg/m³	Not covered here

For daily decisions in an Indian home: in winter, watch PM2.5 and keep it under 60 µg/m³ at the very least, as close to 15 as you can manage in the bedroom. In dusty months, PM10 tells you when to close up and when the sweeping has stirred things up. PM1.0 tells you when something in the room is burning.

Frequently Asked Questions

What is the difference between PM2.5 and PM10?

PM10 is all particulate matter 10 microns or smaller; PM2.5 is the finer part, 2.5 microns or smaller. PM2.5 is counted inside PM10. PM10 in Indian cities is dominated by road dust and construction, while PM2.5 comes mostly from combustion: vehicles, stubble and waste burning, firecrackers, and indoor smoke from cooking and incense.

Which is more harmful, PM2.5 or PM10?

PM2.5 is generally considered more harmful because the particles are small enough to reach deep into the lungs, where they are cleared more slowly. Coarser PM10 particles are mostly trapped in the nose and throat. That is why PM2.5 limits are much stricter. Both are worth reducing, but indoors in winter PM2.5 is the number to watch first.

Why is my PM10 reading always higher than PM2.5?

Because PM10 includes PM2.5. The PM10 figure counts all the fine particles plus the coarser ones between 2.5 and 10 microns, so it is always equal to or higher than PM2.5. A big gap between the two means a lot of coarse dust; readings close together mean the air is mostly fine particles, typical of smoke and winter smog.

Does a HEPA air purifier remove both PM2.5 and PM10?

Yes. A HEPA filter captures both coarse and fine particles, and an H13 grade filter captures 99.95% of particles in a single pass at its rated size. How quickly the room clears depends on the purifier’s CADR relative to the room size and on keeping the door closed. HEPA does not capture gases or odours.

What is PM1.0 and should I worry about it?

PM1.0 is particles 1 micron or smaller, the finest part of PM2.5. It mostly comes from fresh combustion such as vehicle exhaust, incense and cooking smoke. India has no separate standard for it, so treat it as a signal: a sudden PM1.0 spike usually means something is burning in or near the room.

Can an air quality sensor tell if particles are pollen or smoke?

No. Laser particle sensors measure particle size and estimate mass in each size range; they cannot identify what a particle is made of. You can make reasonable guesses from patterns, for example a PM1.0 spike while cooking, but a home sensor cannot confirm pollen, mould spores or smoke specifically.

See PM1.0, PM2.5 and PM10 in your room separately, every second. Boon Airvana pairs a laser particle sensor with an H13 HEPA filter.

See Boon Airvana →

October 16, 2026

What Is a Safe AQI Level Indoors? A Plain Guide for Indian Homes

A safe indoor AQI is 50 or below, the CPCB “Good” band. Anything up to 100 (“Satisfactory”) is acceptable for most healthy people, but children, older family members and anyone with asthma or heart disease do better when the room stays under 50. Above 100 indoors, it is time to close up, filter the air and cut indoor sources of smoke.

If you have searched “AQI kitna hona chahiye”, that is the answer in one line: aim for under 50 inside your home, treat 51 to 100 as fine for a short while, and act once it crosses 100.

The Short Answer

The AQI (Air Quality Index) turns several pollutants into one number on a 0 to 500 scale. Lower is better. In Indian cities during October and November, the number that drives the AQI is almost always fine particulate matter (PM2.5), so in practice “a safe AQI” means “a low level of fine particles”.

India’s AQI and its air-quality standards are written for outdoor air. There is no separate household number that you are required to meet, so the sensible approach is to borrow the outdoor bands and the health-based limits, and hold the air in the rooms where you spend most time, especially the bedroom, to the stricter end of them.

Rule of thumb: under 50 is the goal, under 100 is acceptable, over 100 indoors means you need to act, and over 200 indoors means the room is not protecting you at all.

The CPCB Bands and What to Do Indoors

These are the Central Pollution Control Board’s National AQI bands. The right-hand column is practical guidance for the inside of a home, not an official instruction.

AQI	Band	What to do indoors
0-50	Good	Ventilate freely. Open windows for fresh air, especially after cooking.
51-100	Satisfactory	Fine for most people. Sensitive family members may notice symptoms; a purifier on low or Auto keeps the bedroom in the Good band.
101-200	Moderate	Keep windows mostly closed during the worst hours, ventilate briefly when outdoor air is cleaner, run a purifier in occupied rooms.
201-300	Poor	Windows closed, purifier running continuously in the bedroom and living room, avoid incense and frying without the chimney or exhaust on.
301-400	Very Poor	Treat the bedroom as a clean room: door shut, purifier sized for the room, gaps under doors reduced. Limit outdoor exercise.
401-500	Severe	Same as above, with everyone who is vulnerable kept in the cleanest room. If anyone has breathing difficulty, contact a doctor.

When outdoor AQI goes past 400 or “500+”, the useful question is no longer what the city reads but what your sealed bedroom reads. A correctly sized purifier in a closed room can pull a room far below the outdoor number; an undersized one in a room with an open door cannot. The GRAP stages explained guide covers what the city restrictions at each level mean.

AQI Number vs PM2.5 in µg/m³

This is the most common source of confusion. AQI and PM2.5 are two different scales. PM2.5 is a concentration: micrograms of fine particles in a cubic metre of air (µg/m³). AQI is an index: a 0 to 500 number calculated from that concentration (and from other pollutants), designed so that people can read it at a glance.

A monitor that shows “PM2.5: 60” and one that shows “AQI: 100” may be describing similar air. The numbers are not interchangeable.
India’s AQI is built so that an index of 100 lines up with the 24-hour national standard for each pollutant. For PM2.5, that standard is 60 µg/m³.
Some devices and apps use another country’s AQI formula. The same air can show a different AQI number on two screens, so check which scale your monitor or app uses before comparing.

When in doubt, look at the raw PM2.5 in µg/m³. It is the figure the health limits below are written in.

WHO and Indian Limits for PM2.5 and PM10

Pollutant	WHO 2021 guideline	India NAAQS
PM2.5, 24-hour	15 µg/m³	60 µg/m³
PM2.5, annual	5 µg/m³	40 µg/m³
PM10, 24-hour	Not used in this guide	100 µg/m³
PM10, annual	Not used in this guide	60 µg/m³

The WHO guideline is a health target: the level below which the evidence of harm is weakest. The Indian National Ambient Air Quality Standards (NAAQS) are the legal outdoor limits. The gap between the two is large, which is why an outdoor reading can be “within the national standard” and still be well above what the WHO recommends.

Why Indoor and Outdoor AQI Differ

Many people assume that closing the windows makes indoor air clean. It helps, but fine particles are small enough to travel through gaps around doors, windows, AC ducts and exhaust openings. Without filtration, indoor PM2.5 in a polluted city usually follows the outdoor level, with a lag.

Indoor air can also be worse than outdoor air for short spells, because a home has its own sources:

Cooking, especially frying and tadka, without a chimney or exhaust running. See how Indian cooking affects indoor air.
Agarbatti, dhoop, camphor and mosquito coils.
Dust stirred up by sweeping, dusting and fans.
Firecracker smoke drifting in around Diwali, covered in our Diwali smoke and indoor air guide.

And there is one thing a sealed room gets worse at: carbon dioxide from breathing builds up when windows stay shut. That is not a particle problem and a purifier does not fix it; a short airing when the outdoor air is at its cleanest does.

A Realistic Indoor Target

The WHO 24-hour figure of 15 µg/m³ is hard to hold through a north Indian winter, but it is the right direction. A practical ladder:

Minimum: keep indoor PM2.5 below the 24-hour NAAQS of 60 µg/m³ in every room people use. On the Indian AQI that means staying at or under 100.
Better: keep the bedroom in the Good band (AQI 50 or below) through the night, because that is where most hours of breathing happen.
Best you can practically do: get the bedroom as close to the WHO 24-hour guideline of 15 µg/m³ as your room and purifier allow, especially for children, older relatives and anyone with a lung or heart condition.

Getting there is mostly a matter of sizing. A purifier needs enough Clean Air Delivery Rate (CADR) for the room’s volume, and the door needs to stay shut while it works. The air purifier size calculator gives you the CADR your room needs.

Boon Airvana shows a live AQI on its display and reads PM1.0, PM2.5 and PM10 every second, so you can see whether your bedroom is actually under 50, not just guess.

See Boon Airvana →

How to Know Your Room’s Number

You cannot see or smell PM2.5 reliably, so a number is the only way to know. Two sources together give you the full picture:

Outdoor: the AQI for your city tells you what is pressing on your windows today and whether a short airing makes sense.
Indoor: a laser particle monitor or a purifier with a built-in PM sensor tells you what is in the room. Our guide on how to check air quality at home compares monitors, apps and what each can and cannot measure.

Check the reading at three moments: after cooking, late in the evening when outdoor pollution tends to settle low over cities, and first thing in the morning in the bedroom. If the morning bedroom reading is under 50, your setup is working.

If someone at home has persistent cough, wheezing or breathlessness during smog season, a low indoor AQI helps but it is not a treatment. See a doctor, and tell them about the air at home.

Frequently Asked Questions

What AQI level is safe inside a home?

An indoor AQI of 50 or below, the CPCB Good band, is the target. Between 51 and 100 is acceptable for most healthy people for short periods. Above 100, close windows during the worst hours, cut indoor smoke sources and run a correctly sized air purifier, especially in the bedroom. Children, older people and anyone with asthma or heart disease benefit most from keeping rooms under 50.

AQI kitna hona chahiye ghar ke andar?

Inside the home, AQI should ideally be 50 or less. Up to 100 is acceptable for a short time for healthy adults. If it is above 100 indoors, keep doors and windows shut during peak pollution, avoid incense and smoky cooking without the exhaust on, and run an air purifier sized for the room.

Is AQI the same as PM2.5?

No. PM2.5 is a concentration measured in micrograms per cubic metre. AQI is an index from 0 to 500 calculated from that concentration and other pollutants. On India’s AQI, an index of 100 lines up with the 24-hour PM2.5 standard of 60 µg/m³. Different apps may use different AQI formulas, so compare raw PM2.5 when you can.

Can indoor AQI be worse than outdoor AQI?

Yes, for short spells. Frying or tadka without an exhaust, agarbatti or dhoop, mosquito coils and sweeping can push indoor particle levels above the outdoor reading. In smog season, fine particles also seep in through gaps, so a closed home without filtration usually follows the outdoor level rather than staying clean.

What should I do if my room AQI is above 300?

Shut the door and windows of the room you are using, run an air purifier sized for that room on a high setting or Auto, and avoid any indoor smoke. Keep vulnerable family members in the cleanest room. If anyone has breathlessness, chest tightness or wheezing that does not settle, contact a doctor rather than relying on the purifier.

What PM2.5 level should I aim for indoors?

At minimum, keep indoor PM2.5 below 60 µg/m³, the Indian 24-hour standard. A better goal for the bedroom is the Good AQI band. The health-based target is the WHO 24-hour guideline of 15 µg/m³; it is hard to hold all winter, but getting the bedroom close to it is a reasonable aim with a correctly sized purifier and a closed door.

Want to see your bedroom’s AQI every second instead of guessing? Boon Airvana reads PM1.0, PM2.5 and PM10 and shows a live AQI on its display.

See Boon Airvana →

October 16, 2026

Smart Air Purifier in India: What App, Alexa and Google Home Features Actually Matter

A smart air purifier is one that measures your air accurately and acts on it without you: a laser particle sensor with a numeric PM2.5 readout, an Auto mode that responds quickly, scheduling, and an app that shows trends. Wi-Fi and voice control are useful on top of that, but they are not what makes a purifier smart. A connected purifier with a poor sensor is just a remote-controlled fan.

What Smart Should Mean

The word “smart” is used for anything with Wi-Fi. A more useful test is whether the purifier makes better decisions than you would by hand. That depends on three things, in this order:

Sensing: does it know what is in the air, and how much?
Control: does it act on that reading sensibly, speeding up fast and slowing down once the room is clean?
Connection: can you see, schedule and automate it from your phone or voice assistant?

Most buyers compare the third and ignore the first two. Reverse that order. The CADR and filter still do the actual cleaning, so a smart purifier must also be correctly sized; see the air purifier features that matter for the basics.

Sensors: Which Parameters Matter

Parameter	What it tells you	How useful at home
PM2.5	Fine particles that reach deep into the lungs; the main pollutant in Indian winter smog	Essential
PM10	Coarser dust, pollen-sized particles, construction dust	Very useful, especially in dusty cities
PM1.0	The finest particles, largely from combustion such as smoke and incense	Useful for smoke events
TVOC	Total volatile organic compounds: cooking fumes, cleaners, paints, agarbatti	Useful; shows when to ventilate
CO₂ or eCO₂	How stale a closed room is; eCO₂ is an estimate, not a direct measurement	Useful as a “time to open a window” signal
NO₂	A traffic and combustion gas	Useful for homes near busy roads

Two honest caveats. A purifier cannot remove CO₂; it can only tell you the room needs fresh air. And particle sensors measure particle size, not what the particles are, so no home sensor can tell pollen from dust. For more on reading these numbers, see how to check air quality at home.

Numeric Readout vs Colour Ring

A colour ring that turns from red to green is reassuring, but it hides the information you need. Green might mean a PM2.5 of 10 or of 50, which are very different against the WHO 24-hour guideline of 15 µg/m³ and India’s NAAQS 24-hour limit of 60 µg/m³. A numeric PM2.5 readout lets you check the purifier is doing its job: switch it on in a smoggy room and watch the number fall. It also tells you when the filter is tiring, because the number falls more slowly than it used to.

The quickest test of a smart purifier: does it show PM2.5 as a number, and does that number move when you light an agarbatti across the room?

Auto Mode and Scheduling

Auto mode is where sensing turns into clean air. A good Auto mode reacts within a few minutes to cooking or incense, then steps down once the room is clean, saving electricity and filter life. A poor one either reacts too late or runs loud all the time. Look for a setting that lets you choose an air-quality target rather than just “on”.

Scheduling covers the predictable parts of your day: switch on before you wake, turn on Sleep mode at bedtime, start before you get home. An energy-saving mode that pauses the fan when air is clean and restarts when it worsens helps on milder days.

Boon Airvana reads eight parameters every second, shows them as numbers, and works with the Boon app, Alexa, Google Home and Matter.

See Boon Airvana →

Alexa, Google Home and Matter

Voice control is a genuine convenience when your hands are full or you are already in bed. Check that the purifier works with the assistant you actually use. Matter is a newer smart-home standard designed so that devices from different makers work across platforms; support for it makes a purifier less likely to be stranded if you change ecosystems later. Routines are where it pays off: for example, switching the purifier to high when you say you are cooking.

Insights, Diagnostics and Gimmicks

Worth having: history charts that show when your air is worst (often evenings and early mornings in winter), filter-life tracking based on actual use, alerts that suggest an action (open a window, clean the pre-filter), and self-diagnostics that flag a sensor or motor fault before you notice it.

Usually gimmicks: animations and mood lighting sold as features, “AI” labels with no explanation of what is learned, health scores that cannot be traced back to a measured number, and claims to detect specific allergens. Some purifiers also cannot remove certain pollutants at all; what air purifiers cannot remove explains the limits.

Boon Airvana as an Example

Here is how Boon Airvana lines up against this list, using only its published specifications:

Sensing: the AtmoScan sensor reads PM1.0, PM2.5 and PM10 (laser-based), TVOC, eCO₂ (estimated), NO₂, temperature and humidity, every second.
Display: a full-colour display with watch faces for full metrics, AQI only, an AQI graph, and a High AQI alert screen.
Control: Auto mode follows real-time AQI; Sleep runs quietly through the night; Eco cycles off and on as AQI settles or rises. Four fan speeds, a timer and child lock.
Alerts: fresh air (eCO₂), cooking fume (TVOC), traffic pollution (NO₂), allergy (PM2.5 and PM10 rising), clean pre-filter and change filter. The allergy alert responds to particle levels; it does not identify pollen.
App: modes, scheduling, child lock, air-quality targets, Auto-learn (learns your routine and starts purifying before you get home), a diagnostics report, charts, trends and insight cards.
Connection: works with Amazon Alexa, Google Home and Matter, with continuous self-diagnostics on sensors, filters and motor.

Underneath the smart layer it has a 380 m³/h CADR and an H13 HEPA filter. What it will not do: remove carbon monoxide, add oxygen or tell you which pollen is in the room. Airvana is ₹14,900 at the time of writing.

Frequently Asked Questions

What makes an air purifier smart?

A smart air purifier measures the air accurately and acts on it by itself. That means a laser particle sensor with a numeric PM2.5 readout, an Auto mode that speeds up and slows down sensibly, scheduling, and an app with history and filter tracking. Wi-Fi and voice control add convenience, but without good sensing they do not make a purifier smart.

Do air purifiers work with Alexa and Google Home?

Many connected purifiers do, but not all, and support varies by model. Check the listing for the exact assistant you use. Matter support helps a purifier work across different smart-home platforms. Boon Airvana works with Amazon Alexa, Google Home and Matter, alongside the Boon app.

Is a PM2.5 number better than a colour indicator?

Yes. A colour ring groups a wide range of readings under one colour, so green could mean clean air or merely acceptable air. A numeric PM2.5 readout lets you compare against the WHO 24-hour guideline of 15 µg/m³, check the purifier is lowering the reading, and notice when the filter starts to tire.

Can a smart air purifier measure CO2?

Some include a true CO2 sensor and others show eCO2, an estimate rather than a direct measurement. Either way, a purifier cannot remove CO2. The reading is useful as a signal that a closed room has gone stale and needs fresh outdoor air, which you get by opening a window when the outdoor AQI allows.

Is an app-controlled air purifier worth the extra cost?

It is if the app does useful work: scheduling, remote start before you get home, air-quality targets, filter-life tracking and charts that show when your air is worst. It is not if the app only duplicates the buttons on the machine. Never trade CADR or filter quality for an app.

Can an air purifier sensor detect pollen?

No home particle sensor can identify pollen. Sensors measure particle size, such as PM2.5 and PM10, not what the particles are. A rise in coarse particles during pollen season may include pollen, but it could also be dust. If allergy symptoms persist despite clean readings, see a doctor for testing.

Boon Airvana: eight-parameter AtmoScan sensing, numeric display, the Boon app, Alexa, Google Home and Matter. ₹14,900 at the time of writing.

See Boon Airvana →

October 16, 2026

How Long Should You Run an Air Purifier? 24/7, Overnight, or Only When AQI Is High

During smog season, run your air purifier whenever someone is in the room, which for a bedroom means all night and for a living room means most of the day. Pollution keeps leaking in, so a purifier switched off for a few hours lets the room drift back towards the outdoor level. The easy way to do this without wasting power is Auto mode, which raises and lowers the fan as the room’s air changes.

The Short Answer

Situation	How long to run it
Outdoor AQI Poor, Very Poor or Severe (common October to January in north India)	Continuously in occupied rooms, on Auto. All night in bedrooms.
Outdoor AQI Moderate	Auto mode, mostly in the evening and overnight when pollution tends to build.
Outdoor AQI Good or Satisfactory	Ventilate instead. Run the purifier after cooking, incense or cleaning, or on Auto so it wakes up only when needed.
Someone with asthma or allergies in the room	Lean towards continuous running in their bedroom through the season.

The reason to keep it running is simple: a purifier does not clean a room once and leave it clean. Fine particles keep arriving through gaps around doors and windows, and from cooking, incense and people moving about. When the purifier stops, the room starts heading back towards the outdoor level.

How Long It Takes to Clean a Room

The clean-up time depends on air changes per hour (ACH): how many times the purifier can pass a volume of air equal to the whole room through its filter in an hour. You get it by dividing the purifier’s CADR (in m³/h) by the room’s volume (floor area times ceiling height, in m³).

At 3 ACH, a volume equal to the room’s air passes through the filter about three times an hour.
At 6 ACH, twice as often, so the room clears roughly twice as fast.
A larger room, a higher ceiling, or an open door to the rest of the house all lower the effective ACH.

One air change does not mean the room is fully clean. Clean air from the purifier mixes with the dirty air already in the room, so each pass removes a share of the particles, not all of them. The level falls quickly at first and then more slowly, which is why a purifier needs a few air changes, not one, to bring a polluted room down, and why it has to keep running to hold it there.

For example, Boon Airvana delivers a CADR of 380 m³/h. In a typical 12 × 12 ft bedroom that is more than nine air changes an hour. Across about 484 sq ft with a 3 m ceiling, it is about 2.8 air changes an hour. Our air purifier size guide and the room size calculator work this out for your room.

Rule of thumb: the higher the air changes per hour, the faster the room clears and the more easily it stays clean. A correctly sized purifier on a lower fan speed often does more than an undersized one on maximum.

Doors and Windows: Closed or Open?

Close them while the purifier is working, if outdoor air is polluted. An open window on a smoggy day keeps bringing in fresh particles, and an open door turns a bedroom into a bedroom plus the hallway plus the living room, which spreads the purifier’s work over a much larger volume.

You do not need to seal the room airtight. Normal gaps are fine; the purifier is sized to cope with them. Two caveats:

Carbon dioxide builds up in a closed room with people in it. A purifier does not remove CO₂ or add oxygen. Air the room briefly when outdoor AQI is at its lowest point in the day, then close up again and let the purifier recover the room.
Never close up a room with a gas heater, angithi, coal or charcoal burning. A purifier does nothing for carbon monoxide. See what air purifiers cannot remove.

Where you put the purifier matters too: away from walls and curtains, with clear space around the intake. Our guide on where to place an air purifier covers Indian rooms, fans and ACs.

Boon Airvana’s Auto mode follows the room’s real-time AQI, Sleep mode runs quietly through the night, and Eco mode cycles off and on as the air settles or worsens.

See Boon Airvana →

Running It While You Sleep

Yes, run it overnight. You spend more continuous hours in the bedroom than anywhere else, the door is usually shut, and in many north Indian cities pollution tends to build up in the evening and night. A bedroom purifier that runs from bedtime to morning does more for most people than one that runs in the living room during the day.

Three tips for nights:

Start it before bedtime, so the room is already clean when you lie down.
Use a sleep mode with a dimmed display and a quiet fan, so nobody is tempted to switch it off.
Keep the door shut. An open door roughly undoes the sizing you did.

Auto and Eco Modes: the Practical Answer

Most people do not want to decide every hour whether the purifier should be on. That is what sensor-led modes are for:

Auto mode reads the room’s particle level and raises the fan when pollution rises (cooking, incense, a door opened) and lowers it when the air is clean. It runs continuously but only works hard when needed.
Eco mode (on Airvana) goes a step further: it cycles the purifier off and on as the AQI settles or rises, to save electricity.
Scheduling and timers help where routines are fixed, for example starting the bedroom purifier an hour before bedtime. Airvana’s app also has an Auto-learn mode that learns your routine and starts purifying before you get home.

Only rely on Auto if the purifier has a real particle sensor. A purifier that guesses, or one with a vague dust sensor, may lower the fan while the fine particles are still high.

Electricity and Filter Life

Running a purifier 24/7 does use more electricity than running it for a few hours, but at lower fan speeds most purifiers draw far less than at full speed, which is why Auto and Eco modes matter. The actual cost depends on the model’s power draw, the speed it spends most time at and your tariff; our air purifier running cost guide shows how to work it out.

The bigger running cost is usually the filter. A filter that cleans more air catches more particles and fills faster, so running a purifier through a Delhi winter uses up a filter faster than running it in a clean month. Three habits help:

Wash or vacuum the pre-filter regularly (Airvana’s pre-filter is washable). It catches hair and dust that would otherwise clog the main filter.
Change the main filter when the reminder says it is due, not on a fixed calendar. On Airvana the reminder depends on the air it has actually cleaned.
Do not switch the purifier off to “save the filter” on smoggy days. The filter is there to be used; an unused filter in a polluted room protects nobody.

See air purifier maintenance and filter care for the full routine.

Frequently Asked Questions

Should I run my air purifier 24/7?

In smog season, running it continuously in occupied rooms makes sense, because outdoor particles keep leaking in and the room drifts back to the outdoor level once the purifier stops. Use Auto mode so the fan only works hard when pollution rises. When outdoor AQI is Good or Satisfactory, ventilating the home is often enough.

How long does an air purifier take to clean a room?

It depends on air changes per hour: the purifier’s CADR divided by the room’s volume. At 3 air changes an hour, a volume equal to the room’s air passes through the filter about three times an hour; at 6, twice as often. Each pass removes a share of the particles, so a few air changes are needed to bring a polluted room down.

Should doors and windows be closed when using an air purifier?

Yes, when outdoor air is polluted. An open window brings in fresh particles and an open door spreads the purifier over a larger space. You do not need to seal the room airtight. Air the room briefly when outdoor AQI is lowest to clear carbon dioxide, and never close up a room with a gas heater, angithi or charcoal burning.

Is it safe to run an air purifier all night while sleeping?

Yes, a HEPA air purifier is designed to run for long periods, and the bedroom at night is where it does the most good. Start it before bedtime, keep the door shut and use a sleep mode so the noise and display do not disturb you. Avoid purifiers that produce ozone, especially in bedrooms.

How much electricity does an air purifier use if run 24 hours?

It depends on the model’s power draw at each fan speed, how long it spends at each speed, and your electricity tariff. Purifiers draw much less on low speeds than at full speed, so Auto and Eco modes keep 24-hour running costs down. Check the model’s rated power and use our running cost guide to work out your monthly figure.

Does running an air purifier all the time wear out the filter faster?

Yes, a filter that cleans more air catches more particles and fills sooner, especially in a smoggy winter. That is the filter doing its job. Wash the pre-filter regularly to protect the main filter, and replace the main filter when the purifier’s reminder says it is due rather than on a fixed calendar.

Set it once and let the room decide. Boon Airvana’s Auto mode follows the live AQI, and Eco mode cycles off and on to save electricity when the air is clean.

See Boon Airvana →

October 16, 2026

Do Indoor Plants Purify Air? What the Research Actually Shows

Not in any way you would notice. Indoor plants do absorb small amounts of some gases, but in a normal home the effect is tiny compared with opening a window, and plants do nothing meaningful for PM2.5, the fine particles behind India’s winter smog. Keep plants for how they make a room feel; use ventilation and a HEPA filter for the air.

The Short Answer

Lists of “air purifying plants” are among the most shared home tips in India, usually with the snake plant, money plant, areca palm and peace lily at the top. The claim is not completely invented: plants and the microbes in their soil can take up some volatile chemicals. The problem is scale. A few pots in a living room process a very small volume of air compared with the air that leaks in and out of the room every hour, let alone the air a purifier moves.

Bottom line: plants are good for wellbeing, not for air cleaning. For smog season, the useful tools are ventilation when outdoor air is cleaner, and HEPA filtration when it is not.

Where the Idea Came From: the NASA Study

Almost every “plants clean the air” article traces back to a 1989 NASA study, often called the Clean Air Study. It looked at how houseplants might help clean air in sealed spaces, with a future space station in mind.

The key detail is how it was done. Plants were placed in small, sealed test chambers, a known amount of a chemical was injected, and researchers measured how the level fell over time. In a small sealed box with no fresh air coming in, even a slow removal process shows up clearly.

A home is the opposite of a sealed chamber. Air constantly leaks in and out through doors, windows, gaps and exhausts, and new pollution keeps arriving. The chamber result was real, but it does not transfer to a living room.

What Later Research Found

Researchers have since gone back over the chamber studies and asked the obvious question: how many plants would a real home need to match what ordinary ventilation already does?

A widely cited review by Cummings and Waring, published in 2019, converted the chamber results into a form that can be compared with real buildings. Their conclusion was that you would need an impractically large number of plants per square metre of floor, far more than anyone could fit in a home, to equal the air cleaning that normal air exchange through a building already provides.

In other words, the gas removal plants offer is swamped by the air that moves through a room anyway. Adding a few more pots does not change that.

Why Plants Do Nothing for PM2.5

Even the NASA study was about gases (volatile organic compounds), not particles. That matters in India, because the pollution that sends the AQI into Poor, Very Poor and Severe from October to January is mostly PM2.5: fine particles from vehicles, stubble burning, waste burning and firecrackers.

To remove particles, air has to be pushed through a filter. A plant has no fan and no filter. A few particles land on leaves, but the room’s air is not being drawn past them in any meaningful volume.
Dusty leaves do not mean the plant is “cleaning” the air; settled dust would have settled on the floor or shelf anyway.
No plant reduces carbon monoxide or adds a meaningful amount of oxygen to a room. Neither does an air purifier, for that matter: see what air purifiers cannot remove.

There is also a downside worth knowing. Overwatered pots and constantly damp soil can grow mould, and mould releases spores into the air. For anyone with allergies or asthma, a crowd of wet pots in a bedroom can make the air worse, not better. Let the top of the soil dry between waterings, use pots with drainage, and keep heavily watered plants out of the bedroom of anyone sensitive.

A filter only works if it moves enough air for your room. Find the CADR your room needs before you buy any purifier.

Size Your Room →

Plants vs Ventilation vs a HEPA Purifier

	Indoor plants	Opening windows	HEPA air purifier
PM2.5 and PM10	No meaningful effect	Lowers indoor PM only when outdoor air is cleaner; raises it on smog days	Captures both; how fast depends on CADR vs room size
Gases and odours (VOCs)	Very small effect in a real home	Effective, by diluting with outdoor air	Some, if it has activated carbon; not every gas
Carbon dioxide from breathing	No meaningful effect	Effective	No effect
Works in Severe AQI?	No	No, it brings the smog in	Yes, in a closed room sized correctly
Downsides	Mould risk from wet soil	Lets in dust, noise and smog	Running cost and filter replacement

To the question “do plants clean air better than a budget HEPA purifier?”, the answer is no. Even a modest HEPA purifier sized for the room removes far more particles than any number of plants you could fit in it. Our guide on whether air purifiers actually work covers what a purifier can and cannot be expected to do.

The best combination for most Indian homes: air the house briefly when the AQI for your city is at its lowest point in the day, run a HEPA purifier in the rooms you use when it is high, and control indoor sources such as frying without an exhaust and burning incense in closed rooms.

Keep Your Plants, for the Right Reasons

None of this means you should give your plants away. Greenery at home is widely associated with feeling calmer and more pleasant surroundings, and looking after plants is a good habit. Just do not count them as air-cleaning equipment, especially not for a child, an older parent, or anyone with asthma during smog season.

A few habits keep plants and clean air working together:

Pick hardy, low-water plants that suit your light, so the soil is not wet all the time.
Wipe dusty leaves with a damp cloth rather than dusting them dry, which only puts the dust back into the air.
Keep pots on the balcony or in the living room rather than crowding a bedroom, and check the soil surface and saucers for mould or a musty smell.
Do not let a plant shelf block the intake or outlet of your air purifier; it needs clear space around it to move air.

If the reason you were buying plants was a family member’s cough or wheezing in winter, the plants will not fix it. Get the room’s PM2.5 measured, filter the air properly, and see a doctor if symptoms continue.

Frequently Asked Questions

Do indoor plants really purify the air?

Only very slightly. Plants and their soil microbes can take up small amounts of some gases, but in a normal home that effect is tiny compared with ordinary air exchange through doors and windows. Plants do nothing meaningful for PM2.5, the fine particles behind winter smog in Indian cities. Keep them for wellbeing, not as air cleaners.

What did the NASA plant study actually prove?

The 1989 NASA study found that plants could reduce some volatile chemicals inside small, sealed test chambers. A home is not sealed: air keeps leaking in and out and new pollution keeps arriving. Later analysis, including Cummings and Waring in 2019, concluded you would need an impractically large number of plants per square metre to match normal ventilation.

Do snake plants or money plants remove PM2.5?

No. Removing particles needs air to be pushed through a filter, and plants have neither a fan nor a filter. Some dust settles on leaves, but it would have settled somewhere else anyway. For PM2.5 during smog season, a HEPA air purifier sized for the room is the tool that works.

Are indoor plants better than a budget HEPA air purifier?

No. A HEPA purifier with a CADR suited to the room removes far more particles than any number of plants you could fit in it, and plants do almost nothing for PM2.5. Plants also cannot react when pollution spikes. The budget purifier needs to be sized correctly and have its filter replaced on time to do its job.

Can indoor plants make air quality worse?

They can. Overwatered pots and soil that stays damp can grow mould, which releases spores into the air. That can bother people with allergies or asthma. Use pots with drainage, let the top of the soil dry between waterings, and keep heavily watered plants out of the bedroom of anyone who is sensitive.

Which plants are best for indoor air quality in India?

No plant meaningfully improves indoor air quality in a real home, so choose plants for how easy they are to care for in your light and climate, not for air-cleaning claims. Hardy, low-water plants reduce the mould risk from damp soil. For cleaner air, rely on ventilation when outdoor AQI is low and a HEPA purifier when it is high.

For particles that plants cannot touch, Boon Airvana pushes air through an H13 HEPA filter and shows you the PM2.5 level in the room as it falls.

See Boon Airvana →

October 16, 2026

Air Purifier for Asthma: What Helps, What to Look For, and When to See a Doctor
In This Guide

Does an Air Purifier Help Asthma?

Features That Matter for Asthma

What to Avoid

Triggers a Purifier Cannot Handle

Children With Asthma

When to See a Doctor

Frequently Asked Questions
An air purifier can help some people with asthma by lowering the particles and airborne allergens they breathe at home, particularly in the bedroom and during smog season. It is an add-on to medical treatment, never a replacement for an inhaler, a prescription or a doctor’s plan. Choose an H13 HEPA purifier sized for the room, without an ozone-producing ioniser.

Does an Air Purifier Help Asthma?

The honest answer is: it can help, it does not help everyone equally, and it is never the main treatment. Asthma is a long-term condition of the airways, and the people who manage it best do so with a doctor’s plan: preventer and reliever medicines, knowing their triggers, and a clear idea of what to do in an attack.

Where a purifier fits is in reducing exposure to some of those triggers. General guidance on asthma and allergy management supports cutting exposure to airborne particles and allergens, and a HEPA purifier is one practical way to do that indoors. The effect is most noticeable when:
- Outdoor PM2.5 is high (October to January in much of north India), and the person’s symptoms track the smog.
- The person is sensitive to airborne allergens that a filter can catch, such as dust-mite debris stirred up from bedding or pet dander.
- The purifier runs in the room where the person sleeps, with the door shut, because that is where the most hours of breathing happen.
If dust mites are a suspected trigger, a purifier is only part of the answer. Covers, washing and humidity matter more; our dust mite allergy guide covers that in full.

Keep the order right: doctor’s plan first, trigger control second, clean bedroom air third. A purifier belongs in the third step.

Features That Matter for Asthma

Many purifiers are sold with “asthma” on the box. These are the features that actually make a difference, in order:
1. A true HEPA filter, ideally H13. HEPA is the proven technology for particles. H13 captures 99.95% of particles in a single pass at its rated test size, which covers smoke, fine dust and allergen fragments.
2. Enough CADR for the bedroom. CADR (Clean Air Delivery Rate) is how much clean air the purifier delivers per hour. An undersized purifier with an excellent filter still leaves the room polluted. Size it for the actual room volume, not the box claim.
3. A real particle sensor and Auto mode. A laser PM2.5 sensor lets the purifier react when pollution rises, for example when someone starts cooking or a neighbour burns leaves, rather than running on a fixed speed you forget to change.
4. Quiet enough to run all night. A purifier that is switched off at bedtime because it is too loud does nothing. Look for a sleep mode, and test it in your room during the return period.
5. Easy filter replacement and a reminder. A clogged filter delivers far less clean air. A purifier that tells you when the filter is due is easier to keep effective.
Before you compare models, work out how much CADR your bedroom needs. It takes a minute and stops you buying an undersized purifier.
Size Your Room →

What to Avoid
- Ozone-producing ionisers and “ozone generators”. Ozone is a lung irritant, which is the opposite of what someone with asthma needs. If a purifier has an ioniser, check that it can be switched off, or choose a HEPA-only design. Our guide on HEPA vs ionizer vs UV purifiers explains the difference.
- Fragrance add-ons. Some purifiers and room fresheners add scent. Strong fragrances are a trigger for some people with asthma.
- “Doctor recommended” brand claims. Doctors generally recommend reducing exposure, not a specific brand. If your doctor has advised a purifier, ask them what matters for your case, then compare features against that.
- Moving it from room to room every hour. One purifier sized for the bedroom, left running, does more than one purifier chasing the person around the house.
Triggers a Purifier Cannot Handle

Being honest about the limits matters, because an asthma plan built on the wrong assumption can fail when it is needed most. A purifier does little or nothing for:
- Cold air, exercise and respiratory infections, which are common triggers that have nothing to do with indoor particles.
- Many gases. An activated carbon layer reduces some odours and gases, but it is not a fix for every gas, and a purifier does nothing for carbon monoxide. See what air purifiers cannot remove.
- Allergens that sit in bedding, carpets and soft toys. Dust-mite allergen is heavy and settles quickly; it gets into the air mostly when disturbed. Washing and covers do more than a filter here.
- Damp and mould at the source. A purifier can catch some airborne spores, but a damp wall keeps producing them. Fix the damp.
- Smoke made inside the room. Incense, mosquito coils and smoking indoors put out particles faster than many purifiers can remove them. Removing the source is the bigger win.
Children With Asthma

Many parents search for an air purifier for an asthmatic child, and it is a reasonable thing to consider, especially in north Indian winters. Please make the first step a conversation with your child’s paediatrician: they can confirm the diagnosis, check the child’s medicines and inhaler technique, and help you identify which triggers matter for your child. A purifier can then support that plan in the child’s bedroom.

Practical points for a child’s room: choose a purifier with a child lock so settings are not changed, place it where it cannot be pulled over, keep it running quietly through the night, and avoid any ozone-producing feature. Our guide to an air purifier for a baby’s room covers placement and safety for younger children.

When to See a Doctor

A purifier should never delay medical care. Book a doctor’s appointment if:
- Asthma symptoms wake you or your child at night.
- You are using a reliever inhaler more often than usual, or it helps for a shorter time.
- Symptoms get worse every smog season, or a cough has not settled. Our guide to a constant cough at home covers other causes worth ruling out.
- You have never had a written asthma action plan, or are not sure your inhaler technique is right.
Get emergency help immediately if there is severe breathlessness, breathlessness at rest or difficulty speaking in full sentences, a reliever inhaler that is not helping, blue or grey lips or fingertips, or a child who is struggling to breathe, unusually drowsy or confused. These are emergencies; do not wait to see if the air clears.

Frequently Asked Questions

Does an air purifier help with asthma?

It can help some people by reducing the particles and airborne allergens they breathe indoors, especially in the bedroom during smog season. It does not treat asthma and does not replace inhalers or a doctor’s plan. The benefit depends on the person’s triggers: a purifier helps with airborne particles, not with cold air, exercise, infections or most gases.

What type of air purifier is best for asthma?

Look for a true HEPA filter, ideally H13, with enough CADR for the bedroom, a real PM2.5 sensor with Auto mode, a quiet sleep mode so it can run all night, and filter replacement reminders. Avoid purifiers that produce ozone, such as ozone generators or ionisers that cannot be switched off, because ozone irritates the lungs.

Is an ioniser air purifier safe for someone with asthma?

Some ionisers produce ozone as a by-product, and ozone is a lung irritant, so they are a poor choice for anyone with asthma. If a purifier has an ioniser, check that it can be switched off and run the HEPA filter alone. A HEPA-only design avoids the question entirely. Ask your doctor if you are unsure.

Should my asthmatic child have an air purifier in the bedroom?

It can be a sensible addition, especially in north Indian winters, but speak to your child’s paediatrician first so the purifier supports a proper treatment plan. If you use one, size it for the bedroom, keep the door shut, run it through the night, use the child lock and place it where it cannot be pulled over.

Can an air purifier stop asthma attacks?

No. An air purifier cannot stop or treat an asthma attack. It may reduce exposure to some airborne triggers over time, which helps some people, but attacks need the reliever and action plan your doctor has given you. If a reliever is not helping, or lips turn blue or grey, get emergency medical help immediately.

When should someone with asthma see a doctor during smog season?

See a doctor if symptoms wake you at night, if you are using your reliever more often, if symptoms worsen every winter, or if a cough does not settle. Seek emergency help for breathlessness at rest, difficulty speaking, a reliever that is not working, or blue or grey lips. Clean indoor air supports treatment; it never replaces it.

If your doctor agrees cleaner bedroom air is worth trying, Boon Airvana pairs an H13 HEPA filter with a live PM2.5 sensor, Auto and Sleep modes, and a child lock.
See Boon Airvana →
October 16, 2026

Category: Air Purifier

The Basic Idea: Fan Plus Filters

Stage 1: The Pre-Filter

Stage 2: How HEPA Catches Fine Particles

Stage 3: Activated Carbon for Smells and Gases

What CADR Measures

Sensors, Auto Mode and Why the Room Must Be Closed

What an Air Purifier Does Not Do

A Worked Example: Boon Airvana

Frequently Asked Questions

How does an air purifier work in simple words?

Does a HEPA filter work like a sieve?

What is CADR in an air purifier?

Do air purifiers need the windows closed?

Does an air purifier add oxygen to the room?

How does Auto mode on an air purifier work?

What that smell is

Where it is growing

Why cleaning it off does not work

Fixing the cause

The same problem with smoke odour

When mould is a health issue

Preventing next monsoon

Where an air purifier helps, and where it does not

Frequently Asked Questions

How do I get rid of a musty smell in my house during monsoon?

Why does mould keep coming back on my walls?

Is monsoon mould dangerous to health?

Does an air purifier remove mould smell?

How do I get cigarette smoke smell out of a room?

The Short Answer

Germs, Droplets and What HEPA Can Catch

Filtration Is Not Disinfection

Reading Kills 99.99% Claims

What an Anti-Bacterial Filter Coating Does

What Actually Lowers Infection Risk at Home

Frequently Asked Questions

Can an air purifier remove viruses from the air?

Does a HEPA filter trap bacteria?

Are air purifiers that kill 99.99% of germs real?

What does an anti-bacterial coating on an air purifier filter do?

Can an air purifier stop a cold or flu spreading at home?

Is a UV air purifier better for germs than HEPA?

The Short Answer

Why an Air Purifier Cannot Stop Mosquitoes

UV and Fan Mosquito Traps Are a Different Device

Coils, Vaporisers and Your Indoor Air

What Actually Keeps Mosquitoes Out

Dengue and Malaria: When to See a Doctor

Where a Purifier Does Help

Frequently Asked Questions

Does an anti mosquito air purifier work?

Can an air purifier catch mosquitoes?

Is mosquito coil smoke harmful indoors?

Can I run an air purifier while a mosquito vaporiser is on?

Do mosquito killer machines work?

When should I see a doctor for fever in mosquito season?

What the Numbers Mean

Where Each Comes From in Indian Cities

Why PM2.5 Does More Harm

PM1.0: The Smallest Number on Your Monitor

What Each Kind of Sensor Can See

How a HEPA Purifier Handles Both

Indian Limits and Which Number to Watch

Frequently Asked Questions

What is the difference between PM2.5 and PM10?

Which is more harmful, PM2.5 or PM10?

Why is my PM10 reading always higher than PM2.5?

Does a HEPA air purifier remove both PM2.5 and PM10?

What is PM1.0 and should I worry about it?

Can an air quality sensor tell if particles are pollen or smoke?

The Short Answer

The CPCB Bands and What to Do Indoors

AQI Number vs PM2.5 in µg/m³

WHO and Indian Limits for PM2.5 and PM10

Why Indoor and Outdoor AQI Differ

A Realistic Indoor Target

How to Know Your Room’s Number

Frequently Asked Questions

What AQI level is safe inside a home?