Do air purifiers really work? What they do and don't do in a Delhi home
By the BYM Electronics team · Updated 07 October 2026
Why this matters in Delhi
Delhi's monthly average PM2.5 in November 2025 was 215 µg/m³, according to the Centre for Research on Energy and Clean Air. India's national 24-hour standard is 60 µg/m³ and the World Health Organization's 24-hour guideline is 15 µg/m³. Outdoor air gets indoors through gaps, doors and windows, so indoor air in an ordinary flat follows the outdoor level unless something is filtering it.
What the research says
A 2019 study in the International Journal of Environmental Research and Public Health modelled a typical urban Delhi household. Running a HEPA air filter all day cut a person's PM2.5 exposure from 103 to 29 µg/m³ in a non-smoking home, a 72% reduction. The same study is clear about the limit: outdoor air leaking in is what stops the number going lower, which is why closed windows matter so much.
The US Environmental Protection Agency puts it this way: portable air cleaners "can reduce indoor air pollution; however, they cannot remove all pollutants from the air", and the most effective steps are still to remove pollution sources and ventilate with clean outdoor air when it is available.
What an air purifier does and doesn't do
| People ask | Answer |
|---|---|
| Does it remove dust? | It removes dust that is floating in the air. Dust already on shelves and floors still needs wiping, though less new dust settles when a purifier runs. |
| Does it remove smells and cigarette smoke? | Smoke particles, yes (HEPA). Smells and gases need an activated carbon layer; check the filter description for one. No purifier makes indoor smoking safe. |
| Does it help with allergies? | It lowers airborne pollen, pet dander and dust-mite particles in the room. Whether symptoms improve varies from person to person; treat it as one part of managing allergies and follow your doctor's advice. |
| Does it reduce humidity or make the air dry? | No. A purifier only filters air; it neither adds nor removes moisture. See our purifier vs humidifier vs dehumidifier guide. |
| Does it cool the room? | No. It moves air like a small fan but does not lower the temperature. |
| Can I use it with an AC? | Yes, and they work well together: a split AC recirculates room air, so you can keep windows shut while the purifier cleans it. |
| Does it use a lot of electricity? | No. Most home purifiers draw less power than a ceiling fan. See the running-cost guide. |
| Are there side effects? | A purifier that cleans by filtration alone (pre-filter, HEPA, carbon) adds nothing to the air. Avoid devices sold as "ozone generators" for occupied rooms. The practical downsides are fan noise at high speed and the cost of replacement filters. |
Is it worth the money?
It is worth it if you will actually use it the way it works: in a room you spend hours in (usually the bedroom), with the door and windows closed, sized correctly, with the filter replaced on time. It is not worth it for a room that stays open to a balcony or corridor, or if it will run on the lowest speed in a room twice its rated size.
The running costs are small next to the purchase price: electricity is typically a few rupees a day, and a filter is usually needed about once a year (some Philips filters are rated for longer).
How to make a purifier work properly
- Size it for the room. Use the brand's rated room size as the maximum, and prefer a model whose CADR in m³/h is at least 1.1 times your room area in sq ft. See the room-size guide.
- Shut the doors and windows while it runs.
- Run it continuously on auto. Pollution leaks back in within minutes of switching it off.
- Give it space: keep it a little away from walls and curtains so air can flow in and out.
- Clean the pre-filter every two to four weeks and replace the main filter when the indicator says so.
Air purifiers we stock, by room size
Not sure which fits your room? WhatsApp us your room size.
Sources
- Centre for Research on Energy and Clean Air: Monthly ambient air quality snapshot for India, November 2025
- Liao, Ye, Pillarisetti and Clasen (2019): Modeling the impact of an indoor air filter on air pollution exposure reduction and associated mortality in urban Delhi households
- US EPA: Air cleaners and air filters in the home
Frequently asked questions
Do air purifiers really work?
Yes, for airborne particles. A correctly sized HEPA purifier in a closed room removes most fine dust and smoke (PM2.5) from the air. A 2019 modelling study of Delhi households found all-day HEPA filtration cut PM2.5 exposure by about 72%.
Is an air purifier worth it in Delhi?
It is worth it for a room you spend many hours in, such as a bedroom, if you keep doors and windows closed and size the purifier for the room. It does little in a room that stays open to outside air.
Does an air purifier remove dust from a room?
It removes dust floating in the air and slows new dust from settling. It does not lift dust that has already settled on surfaces.
Does an air purifier reduce humidity or dry the air?
No. An air purifier only filters particles and, with a carbon filter, some gases and odours. It does not change humidity.
Can I use an air purifier with an AC?
Yes. A split AC recirculates indoor air, so the two work well together with the windows closed.