How to Choose an Air Purifier for Home in India: A Complete Decision Framework

To choose an air purifier for home, start with the room: work out the CADR it needs, then insist on a true HEPA filter in a sealed housing, a sensor that shows real numbers, and a running cost you can live with. Smart features and design come last. Follow the five steps below in order and most models eliminate themselves.

Step 1: Room Size and CADR

CADR, Clean Air Delivery Rate, is how many cubic metres of clean air a purifier delivers every hour. It is the single number that decides whether a purifier will make a difference you can feel. Everything else on the box is secondary.

To find what your room needs, multiply floor area by ceiling height to get the volume, then multiply by the number of air changes per hour (ACH) you want. For Indian winters, aim for about four to five air changes an hour in a bedroom. A 12 × 12 ft bedroom with a 3 m ceiling holds about 40 m³, so it needs roughly 160 to 200 m³/h.

Measure the room you will actually use it in, not the one you hope it will cover. If you plan to move it between rooms, size it for the largest. The air purifier size calculator does the arithmetic in a few seconds.

Step 2: Filter Grade and Seal

A true HEPA filter is the part that captures fine particles such as PM2.5. Look for a named grade; H13 is the common standard in home purifiers. Avoid “HEPA-type” or “HEPA-like” media, which is not graded to a HEPA standard.

Two things matter as much as the grade. First, the seal: air that leaks around the filter is not cleaned. Second, activated carbon: a layer of carbon helps with cooking smells and some gases, which HEPA cannot catch. More carbon generally helps more; a token dusting does little. A washable pre-filter that catches hair and large dust is a welcome bonus because it protects the HEPA layer.

Step 3: Sensor Quality

The sensor decides when the fan speeds up and slows down. A good one makes Auto mode useful; a poor one makes it either lazy or noisy.

• Laser particle sensors count particles by size and can show PM2.5 as a number. They are the better choice.
• Infrared sensors are cheaper and coarser, and are usually paired with a colour light rather than a number.
• A numeric display lets you check the purifier is working: watch PM2.5 fall after you switch it on. A colour ring alone tells you very little.

Gas sensors (TVOC, NO₂, estimated CO₂) are useful extras for kitchens and homes near traffic, not essentials. The trade-offs are covered in the air purifier features that matter.

Step 4: Smart Features Worth Having

App control earns its place if it does something you would otherwise do by hand: scheduling, remote start before you get home, filter-life tracking, and history charts that show when your air is worst. Voice control through Alexa or Google Home is a convenience. A child lock matters if you have small children. Features that only add colours or animations are design choices, not air cleaning.

Step 5: Noise, Running Cost and Service

Noise. A purifier in a bedroom runs all night, so noise decides whether you keep it on. Check the stated noise figure in dB at the lowest speed or Sleep mode, and be wary of listings that give no figure. A purifier with plenty of CADR can run at a lower, quieter speed and still keep up. For how air and sleep connect, see bedroom air quality and sleep.

Running cost. Replacement filters are usually the larger running cost, then electricity. Look up the current filter price for the exact model, and prefer a unit with an Auto or Eco mode that slows down once the room is clean. The full sums are in our guide to air purifier running cost in India.

Filters and service. Before you buy, confirm that replacement filters are listed and in stock, and that someone will answer if the unit develops a fault. A purifier you cannot get a filter for is a fan. Good habits after purchase are covered in air purifier maintenance and filter care.

The Checklist

Check	What good looks like	Red flag
CADR	Stated in m³/h, enough for 4 to 5 ACH in your room	Coverage in sq ft only
Filter grade	True HEPA with a named grade, such as H13	“HEPA-type”, “HEPA-like”
Seal	Filter seats firmly with a gasket	Loose filter, visible gaps
Carbon	A real activated-carbon layer	No carbon, or carbon not mentioned
Sensor	Laser particle sensor, numeric PM2.5	Colour light only
Auto mode	Fan responds within minutes to cooking or incense	Stays on one speed regardless
Night noise	Stated dB figure at the lowest speed	No noise figure given
Ozone	No ioniser, or one you can switch off	Always-on ioniser or “plasma”
Filters	Listed, in stock, price known	Not available to buy
Service	A clear way to reach the brand	Marketplace seller only

If you or a family member has breathing difficulty, chest tightness or a cough that does not settle, see a doctor. A purifier reduces exposure to particles; it does not treat a condition.

A Worked Example: Boon Airvana

Here is how Boon Airvana reads against the framework, using only its published specifications:

• CADR: 380 m³/h. About 484 sq ft at a 3 m ceiling (around 2.8 air changes an hour), and more than nine air changes an hour in a 12 × 12 ft bedroom.
• Filter: dual suction through two filters, with a washable pre-filter mesh, H13 HEPA, activated carbon and an anti-bacterial coating on the filter.
• Sensor: AtmoScan reads PM1.0, PM2.5 and PM10 (laser-based), plus TVOC, estimated CO₂, NO₂, temperature and humidity every second, shown as numbers on a full-colour display.
• Modes: Auto, Sleep and Eco, four fan speeds, a timer and a child lock.
• Smart: the Boon app adds scheduling, air-quality targets, Auto-learn, a diagnostics report and trend charts, and works with Alexa, Google Home and Matter.
• Filters: a change-filter reminder based on the air it has cleaned; the pre-filter is washable.

Where it does not fit: a hall much larger than about 484 sq ft is better served by two units placed apart, and no purifier helps with carbon monoxide. Airvana is ₹14,900 at the time of writing.

Frequently Asked Questions

How do I choose an air purifier for my home?

Start with the room. Multiply floor area by ceiling height and by four to five air changes an hour to get the CADR you need. Then insist on a true HEPA filter, ideally H13, in a sealed housing, plus activated carbon. After that, compare sensor quality, night-time noise, running cost and filter availability. Smart features are tie-breakers, not reasons to buy.

What size air purifier do I need for my room?

Size by CADR, not by the coverage claim on the box. Room volume in cubic metres multiplied by the air changes per hour you want gives the CADR in m³/h. A 12 by 12 ft bedroom with a 3 m ceiling needs roughly 160 to 200 m³/h for four to five air changes an hour. The Boon size calculator does this for any room.

Is one air purifier enough for the whole house?

Usually not. A purifier cleans the room it is in, and walls and doors limit how far its airflow reaches. Put one in the room where you spend the most hours, which for most families is the bedroom at night. Add a second for the living room if needed, rather than buying one large unit and expecting it to reach every room.

Which matters more, CADR or HEPA grade?

CADR, for most homes. A sealed H13 filter in a purifier with too little airflow will clean a room slowly, while a correctly sized unit with a good HEPA filter cleans it fast. The filter grade sets how much is caught per pass; CADR sets how often the room’s air passes through. You need both, but size first.

How quiet should an air purifier be for a bedroom?

Check the stated noise figure in dB at the lowest speed or in Sleep mode, and compare models on that number. Be cautious with listings that give no figure. A purifier with more CADR than the room strictly needs can run at a lower, quieter speed through the night and still keep the air clean.

Should I buy an air purifier with an app?

An app is worth having if it does useful work: scheduling, starting the purifier remotely before you get home, tracking filter life and showing when your air is worst. It does not make the air cleaner by itself. If the choice is between a better filter and fan or an app, choose the better filter and fan.