Air purifiers for a home office in India: an indoor air quality guide

If you work from home in Delhi, Lucknow, Kolkata or most of the Indo-Gangetic plain, you already know the pattern. From late October the sky turns beige, the AQI app goes from yellow to purple, and by mid-afternoon you have a dull headache that coffee does not fix. Your office used to have central filtration you never thought about. Your spare bedroom does not.

An air purifier is one of the few home-office purchases that changes how the working day feels. It is also a category full of inflated claims. This guide covers what actually matters when you buy one for the room you work in, and how to tell whether it is doing anything.

Know what you are filtering

Outdoor pollution in Indian cities during winter is dominated by fine particulate matter, PM2.5. These particles are small enough to get deep into the lungs, and they come indoors easily through window gaps, door frames and every time someone walks in. Indoors you add your own sources: cooking smoke, incense and agarbatti, mosquito coils, dust, and in older buildings, damp and mould.

A good purifier deals well with particles. It deals much less well with gases. If your main problem is cooking fumes or a new-furniture smell, ventilation and an exhaust fan matter more than any filter. Keep that in mind when a box promises to remove “99.99% of all pollutants”.

Read the AQI properly

India’s National Air Quality Index, published by the Central Pollution Control Board, runs in bands: Good (0 to 50), Satisfactory (51 to 100), Moderate (101 to 200), Poor (201 to 300), Very Poor (301 to 400) and Severe (above 400). Many phone apps use the US EPA scale instead, which is stricter at the lower end, so the same air can show as “Moderate” on one app and “Unhealthy” on another. Pick one source and stick to it.

The figure that matters for your room is the indoor one. A basic laser PM2.5 monitor costs far less than a purifier and tells you whether the machine is working. Without one, you are trusting the purifier’s own display, which on cheaper models is often optimistic.

The one number to compare: CADR

Clean air delivery rate, or CADR, is how much filtered air a purifier delivers, usually in cubic metres per hour or cubic feet per minute. It is the single most useful number on the box, because it combines airflow and filter efficiency.

The common rule of thumb, from the US appliance association AHAM, is that the smoke CADR in cubic feet per minute should be at least two thirds of the room’s floor area in square feet. A 120 square foot study (about 11 square metres, a typical spare bedroom) therefore wants a CADR of at least 80 CFM, roughly 135 cubic metres per hour.

In Indian winters, buy above that. The rule assumes moderately polluted outdoor air, and you will want the machine to cope on its lower, quieter speeds rather than running flat out beside your laptop all day. A practical target for a work room is a CADR of 1.5 to 2 times the minimum.

Be wary of models that quote a “coverage area” without a CADR figure. Coverage areas are calculated in different ways by different brands and are not comparable.

HEPA, “True HEPA” and the marketing around it

A HEPA filter is a dense mat of fibres that traps fine particles. The term is a standard, not a brand, and the grade matters:

• H13 and H14 (under the European EN 1822 standard) are the grades to look for. H13 captures at least 99.95% of particles at the size filters find hardest to catch.
• “True HEPA” is US marketing language for filters meeting the US Department of Energy standard of 99.97% at 0.3 microns. Fine, but check it is stated, not implied.
• “HEPA-type” or “HEPA-like” filters do not meet either standard. Avoid them.

Most purifiers also include an activated carbon layer for odours. A thin carbon sheet does very little. If smells matter to you, look for a filter with a meaningful weight of carbon granules, and expect to replace it more often.

Features that matter and features that do not

Worth having:

• A real PM2.5 sensor with a numeric readout, so you can see what is happening.
• A quiet low or night mode. You will be on video calls next to this machine. Look for a noise figure in decibels at the speed you will actually use, ideally under about 40 dB.
• Easy filter access and filters that are actually sold in India, with a stated replacement interval.

Not worth paying for:

• Ionisers and “plasma” features. Some produce ozone, which irritates the lungs. If a model has an ioniser, check you can switch it off.
• UV lamps in compact purifiers. Air passes too quickly for meaningful exposure.
• App features you will use once. A physical button is more reliable.

Never buy an “ozone generator” sold as an air cleaner. Ozone is a lung irritant, not a cure.

The real cost is the filter

The purifier is a one-off. Filters are forever. In a Delhi winter, with the machine running eight to ten hours a day, a filter rated for twelve months can need replacing in six to eight. Before you buy, find the price of a genuine replacement filter and work out the yearly running cost. A cheaper machine with expensive or hard-to-find filters is the worse deal.

Watch out for counterfeit filters on marketplaces. They often fit the machine but lack proper HEPA media. Buy from the brand or an authorised seller, and be suspicious of filters at a fraction of the usual price.

Set it up so it works

Placement and habits make more difference than most people expect:

1. Close the room. A purifier cleans the room it is in. Keep the door shut while you work and close windows on bad-air days.
2. Give it space. Keep it a short distance from walls and furniture so intake and outlet are clear. Do not hide it under the desk.
3. Run it before you start. Switch it on 30 to 60 minutes before your working day so the room is clean when you sit down.
4. Ventilate briefly, at the right time. You still need fresh air for carbon dioxide. Open a window for a few minutes when outdoor AQI is lowest, often early afternoon, then close it and let the purifier catch up.
5. Cut indoor sources. Skip incense and mosquito coils in the work room, and use the kitchen exhaust when cooking.

Is it worth it for your situation?

If you live in a high-pollution city and spend most of your working day in one room, a properly sized purifier is among the better health purchases you can make for a home office. If you live somewhere with consistently satisfactory air, a monitor plus good ventilation may be all you need.

If you are negotiating a remote or hybrid arrangement, it is reasonable to ask whether your employer’s home-office allowance covers air purification, especially in north India. Some do. Our guide on how to ask for remote or hybrid work covers how to frame that kind of request, and if winter fatigue is starting to look like something more, see how to recognise and recover from burnout.

Start with the cheapest step: buy a PM2.5 monitor, check your work room on a bad day, and size the purifier to the number you see.

This article is general information, not medical advice. People with asthma, heart or lung conditions should take advice from a doctor about air pollution exposure.