Chat with us
Contact For Business
Cart

Tag: indoor air quality

  • 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 sourcesRoad dust, construction and demolition, unpaved ground, wind-blown soilVehicle exhaust, stubble and crop-residue burning, wood and waste burning, industry, firecrackers
    Main indoor sourcesSweeping, dusting, shaking bedding, fans lifting settled dustFrying and tadka, agarbatti and dhoop, mosquito coils, smoking, candles
    How they behaveSettle out of the air relatively quickly; come back up when disturbedStay suspended for a long time; travel far and slip through gaps
    When they peakDry, windy days; near construction; summer dustStill, 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

    StandardPM2.5PM10
    India NAAQS, 24-hour60 µg/m³100 µg/m³
    India NAAQS, annual40 µg/m³60 µg/m³
    WHO 2021 guideline, 24-hour15 µg/m³Not covered here
    WHO 2021 guideline, annual5 µg/m³Not 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 →

  • 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.

    AQIBandWhat to do indoors
    0-50GoodVentilate freely. Open windows for fresh air, especially after cooking.
    51-100SatisfactoryFine for most people. Sensitive family members may notice symptoms; a purifier on low or Auto keeps the bedroom in the Good band.
    101-200ModerateKeep windows mostly closed during the worst hours, ventilate briefly when outdoor air is cleaner, run a purifier in occupied rooms.
    201-300PoorWindows closed, purifier running continuously in the bedroom and living room, avoid incense and frying without the chimney or exhaust on.
    301-400Very PoorTreat the bedroom as a clean room: door shut, purifier sized for the room, gaps under doors reduced. Limit outdoor exercise.
    401-500SevereSame 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

    PollutantWHO 2021 guidelineIndia NAAQS
    PM2.5, 24-hour15 µg/m³60 µg/m³
    PM2.5, annual5 µg/m³40 µg/m³
    PM10, 24-hourNot used in this guide100 µg/m³
    PM10, annualNot used in this guide60 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:

    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:

    1. 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.
    2. Better: keep the bedroom in the Good band (AQI 50 or below) through the night, because that is where most hours of breathing happen.
    3. 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 →

  • 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

    SituationHow 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 ModerateAuto mode, mostly in the evening and overnight when pollution tends to build.
    Outdoor AQI Good or SatisfactoryVentilate 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 roomLean 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:

    1. Start it before bedtime, so the room is already clean when you lie down.
    2. Use a sleep mode with a dimmed display and a quiet fan, so nobody is tempted to switch it off.
    3. 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 →

  • 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 plantsOpening windowsHEPA air purifier
    PM2.5 and PM10No meaningful effectLowers indoor PM only when outdoor air is cleaner; raises it on smog daysCaptures both; how fast depends on CADR vs room size
    Gases and odours (VOCs)Very small effect in a real homeEffective, by diluting with outdoor airSome, if it has activated carbon; not every gas
    Carbon dioxide from breathingNo meaningful effectEffectiveNo effect
    Works in Severe AQI?NoNo, it brings the smog inYes, in a closed room sized correctly
    DownsidesMould risk from wet soilLets in dust, noise and smogRunning 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 →

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

    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 →

  • Agarbatti and Dhoop Smoke: How It Affects Indoor Air, and How to Keep the Ritual Safer

    Agarbatti, dhoop, sambrani, camphor and mosquito coils all release smoke, and smoke means fine particles (PM2.5 and PM1.0) plus volatile organic compounds (VOCs). In a closed room that adds up, especially for children and anyone with asthma. You do not have to give up the ritual: ventilate while and after you burn, use fewer sticks, and let the air clear before people settle in.

    What Is in Agarbatti and Dhoop Smoke

    For many Indian families, lighting an agarbatti or dhoop is part of the day: at the mandir corner in the morning, during puja, or in the evening. Any time something smoulders, it gives off two kinds of pollution:

    • Fine particles. The visible haze from incense is made of very small particles, mostly in the PM2.5 and PM1.0 range. These are the same size class as the particles in winter smog, which is why a home monitor often shows a sharp jump within minutes of lighting a stick.
    • Gases and VOCs. The fragrance, plus the products of incomplete burning. Some of these irritate the eyes, nose and throat. A TVOC sensor picks up the overall rise, though it cannot tell you which chemicals are present.

    How much it matters depends on dose: how many sticks, for how long, in how small a room, with how much fresh air. A single stick near an open window is very different from several sticks of dhoop in a closed bedroom in December, when the outdoor air is too smoky to open up.

    The simple principle: the ritual is not the problem; the closed room is. Smoke that can leave quickly does far less harm than smoke that has nowhere to go.

    Who Should Be Most Careful

    • Babies and young children, who breathe faster for their size and spend long hours indoors. See our guide to an air purifier for a baby’s room.
    • Anyone with asthma, allergies or a chronic lung condition. Smoke is a common trigger. If incense seems to set off cough or wheezing, talk to a doctor.
    • Older family members and anyone with heart disease.
    • Everyone during smog season, because indoor smoke adds to particles that are already high and you cannot air the room as freely.

    Keep the Ritual, Protect the Air

    These steps let you keep the practice with much less smoke in the air you breathe:

    1. Burn near a window or door that can stay open. Even a few minutes of open window during and after lighting lets most of the smoke leave instead of spreading through the house.
    2. Ventilate after, not just during. Smoke lingers. Keep the window open, or the exhaust running, for a while after the stick has burnt out.
    3. Use fewer sticks. One agarbatti in place of three is a real cut in smoke with no change to the meaning of the practice.
    4. Choose the room. Avoid lighting dhoop in bedrooms, especially a child’s room or the room of someone with asthma, and keep them out of the room until the air clears.
    5. Consider lower-smoke options for daily use. Some families keep a single diya, an electric diya, fresh flowers or dhoop only on special occasions. These are personal choices; there is no single right answer.
    6. In smog season, time it. When outdoor AQI is Very Poor or Severe, you cannot ventilate freely, so keep the burning short and run a purifier in the room afterwards. Check the AQI for your city to pick the cleaner part of the day.

    Diwali brings all of this together with firecracker smoke outside. Our Diwali smoke and indoor air guide covers the festival nights specifically.

    Mosquito Coils and Camphor

    Mosquito coils smoulder for hours, often in a closed bedroom overnight. That long, slow burn in a sealed room is exactly the pattern to avoid. Nets, window and door screens, and non-burning repellents avoid the smoke entirely. If you do use a coil, use it in a ventilated space and not in the room where someone is sleeping.

    Camphor (kapur) burns with a bright, sooty flame. Burn small pieces, in a ventilated space, and keep the camphor itself out of children’s reach.

    Boon Airvana’s TVOC and PM sensors notice incense smoke within seconds and raise its fan in Auto mode, then show you on the display when the room has cleared.

    See Boon Airvana →

    What an Air Purifier Can and Cannot Do

    A common question is whether an air purifier removes agarbatti or dhoop smoke, and its smell. The honest answer is: the particles, largely yes; the smell, partly.

    Part of the smokeWhat a purifier does
    Fine particles (PM2.5, PM1.0)A HEPA filter captures them. An H13 filter captures 99.95% of particles in a single pass at its rated size. How fast the room clears depends on CADR and room size.
    Smell and VOCsAn activated carbon layer reduces some odours and gases. It does not remove all of them, and a strong fragrance may linger.
    Carbon monoxide from burningNothing. No air purifier removes carbon monoxide. Ventilation is the only answer.
    Smoke while the stick is still burningA purifier is fighting a source that keeps producing. Ventilation does more during burning; the purifier helps most after.

    So a purifier is a good partner to ventilation, not a replacement. It is also not a reason to burn more incense in a closed room. Our guide on what air purifiers cannot remove explains the gas side in more detail, and the same logic applies to tadka smell, covered in Indian cooking and indoor air.

    How to Tell if the Air Has Cleared

    Smell is a poor guide: your nose gets used to a fragrance within minutes, while fine particles stay invisible. A laser particle monitor, or a purifier with a built-in PM sensor, shows you the real pattern. Watch PM2.5 and PM1.0 jump when the agarbatti is lit, then fall back once the window is open or the purifier has run for a while. If a TVOC reading is available, watch that too; it often stays up a little longer than the particles.

    Once you have seen the pattern a few times, you will know how long your room needs, and you can plan puja time and family time around it without guessing.

    Frequently Asked Questions

    Is agarbatti smoke harmful to health?

    Agarbatti smoke contains fine particles and volatile organic compounds, and in a closed room it can push indoor PM2.5 up sharply. Occasional use in a ventilated space is a much smaller exposure than several sticks daily in a closed bedroom. Children, older people and anyone with asthma are more sensitive. If smoke triggers cough or wheezing, speak to a doctor.

    Does an air purifier remove agarbatti smoke?

    A HEPA air purifier captures the fine particles in incense smoke, and an H13 filter captures 99.95% of particles in a single pass at its rated size. An activated carbon layer reduces some of the smell and VOCs, but not all. Ventilation works better while the stick is burning; the purifier is most useful once it has burnt out.

    Does an air purifier remove the smell of tadka or agarbatti?

    Partly. Smell comes from gases, which a HEPA filter does not catch. An activated carbon layer reduces some odours and VOCs, so the smell fades faster, but strong smells can linger. For tadka, run the chimney or exhaust while cooking; for agarbatti, open a window during and after burning, and let the purifier handle what remains.

    Is dhoop smoke worse than agarbatti smoke?

    It depends more on how much you burn and where than on the type. Dhoop and sambrani often produce thick visible smoke over a short time, while agarbatti burns longer with less visible smoke. Either can raise indoor particles sharply in a closed room. Burn less, near an open window, and keep sensitive family members out until the air clears.

    Are mosquito coils safe to use in a bedroom?

    A mosquito coil smoulders for hours, so in a closed bedroom it keeps adding smoke all night. That is the pattern to avoid, especially around children or anyone with asthma. Nets, window screens and non-burning repellents avoid the smoke. If you use a coil, keep it in a ventilated space rather than the room where someone sleeps.

    How long should I ventilate after lighting incense?

    There is no fixed time; it depends on the room size, how many sticks you burnt and how much air moves through. Keep a window open during burning and for a while after. A PM2.5 monitor or a purifier with a particle sensor shows you when the reading is back to where it was before you lit the stick.

    Keep the ritual and see the air clear. Boon Airvana’s PM and TVOC sensors show incense smoke as it rises and falls, and its H13 HEPA filter captures the particles.

    See Boon Airvana →