🌬️ Air purifier FAQ
Air Purifier FAQ: Straight Answers, No Sales Pitch
These are the questions we are asked most often, answered as briefly as they can honestly be answered. Where a question deserves more than three sentences, the link under each answer goes to the page that treats it properly.
One framing worth having before you read the rest: an air purifier is a fan and a set of filters. There is no chemistry and nothing exotic happening. What separates a good unit from a poor one is how much air it moves against filter resistance, how well the body seals so air cannot bypass the media, and how much genuine filter media is inside — and all three of those are things you can check on a spec sheet.
Do they work, and what do they remove?
Do air purifiers actually work?
Yes, within defined limits: in a closed room, with a correctly sized unit and a filter that is not exhausted. Independent testing consistently shows well-sized HEPA purifiers reducing indoor PM2.5 by 50-90%. They cannot clean a room with the windows open or cover a whole flat from one corner.
Do air purifiers remove dust?
Airborne dust, yes — a true HEPA filter captures it very effectively. Settled dust on furniture and floors, no. A purifier reduces what you breathe and slows how fast surfaces re-dust, but it does not replace cleaning or stop dust arriving on shoes and clothing.
Do air purifiers remove smells?
Only the activated carbon stage does. Odour molecules are gases that pass straight through a HEPA filter. How well and for how long depends on how much carbon the unit actually contains — which varies from a 40 g coated mesh to a 1.2 kg granular bed.
Do air purifiers help with allergies?
Meaningfully for pollen, pet dander and airborne mould spores, particularly in a bedroom with the door closed overnight. For dust mite allergy they are secondary — mites live in bedding, so hot washing, mattress encasings and humidity under 50% do more.
Do air purifiers reduce CO2 or humidity?
Neither. Carbon dioxide is not filtered or adsorbed by anything in a domestic purifier, and only fresh air reduces it. Humidity needs a dehumidifier, which is a separate appliance. A purifier addresses particles and gases, and nothing else.
Sizing and specifications
What CADR do I need for my room?
Aim for CADR in m³/h of at least 5 times your room's floor area in square metres — so a 15 m² bedroom wants at least 75 m³/h. Then size up: one class in a normal city, two in Delhi NCR, because manufacturer figures assume a sealed room you do not have.
What does H13 mean, and is 'HEPA-type' the same thing?
H13 is a grade requiring at least 99.95% efficiency at the most-penetrating particle size. 'HEPA-type', 'HEPA-like' and 'HEPA-style' meet no standard at all and typically test at 85-95% — which lets through 10 to 100 times more particles. Check the grade printed on the filter, not the carton.
How many air purifiers do I need for a 2 BHK?
Two or three: one per bedroom, and optionally one in the living room. Purified air does not travel usefully through doorways, so one unit cleans one room. Two ₹15,000 units in bedrooms beat one ₹30,000 unit in the hall for almost every household.
Should I turn the ioniser on my air purifier off?
Yes, in most cases. The HEPA stage does essentially all the useful work, an ioniser mostly relocates particles onto surfaces rather than removing them, and some designs produce ozone as a by-product. Switching it off costs you nothing meaningful.
Running and maintaining one
Should I run my air purifier all night?
Yes — overnight in a closed bedroom is the highest-value period a purifier gets. Use sleep or auto mode, keep the door shut, and pick a unit quiet enough that you actually leave it on. Electricity costs roughly ₹80-250 a month running continuously.
Where should I place an air purifier?
In the room you occupy longest with the door closed, with at least 30 cm of clearance on all sides, slightly raised if the design allows, and out of an AC's direct airstream. Corners, alcoves and spaces behind curtains are the common self-inflicted performance losses.
How often should air purifier filters be changed?
In Indian conditions expect 6-9 months from a HEPA rather than the 12 usually quoted, and 4-8 months from carbon — which saturates silently with no drop in airflow. Wash the pre-filter every 2-4 weeks; that single habit does most to extend the HEPA's life.
How much electricity does an air purifier use?
Most domestic units draw 15-60 W depending on fan speed, which is roughly ₹80-250 a month running continuously. Filters cost considerably more than the electricity, so running it continuously on auto is both cheaper and more effective than short bursts on high.
Can HEPA filters be washed and reused?
No. Washing collapses the fibre structure, destroys any electrostatic charge in the media, and leaves damp fibres that grow mould. Wash the pre-filter, which is designed for it, and replace the HEPA on schedule.
Air purifiers versus other appliances
Does my AC already clean the air?
No. A split AC's filter is a coarse mesh designed to keep dust off the evaporator coil, and it lets PM2.5 through almost completely. Models with an added PM2.5 layer help a little but rarely publish a CADR and only filter while the fan is running.
Does an air cooler purify the air?
No — and on a high-AQI day it makes indoor air worse, because it continuously draws unfiltered outdoor air through a wet pad. It also raises humidity by 15-30 points, which encourages dust mites and mould.
Is an exhaust fan better than an air purifier?
For indoor-generated pollution — cooking fumes, gas combustion, bathroom moisture, solvent fumes — yes, and it is not close. For outdoor-origin pollution like winter smog it does the reverse. The rule: if the source is inside, ventilate; if it is outside, seal and purify.
Can an air purifier replace a kitchen chimney?
No. A chimney extracts fumes at the source before they disperse; a purifier can only treat what has already spread through the room. Use extraction while cooking and a purifier for the residual load afterwards.
Question not answered here?
Tell us your city and your situation and we will give you a straight answer — including when the honest answer is that you do not need to spend much at all.