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Is your air purifier useless?

Most brands sell them on high-sounding technology and lots of jargon

brunch Updated: Dec 16, 2017 21:14 IST
Rajiv Makhni
Rajiv Makhni
Hindustan Times
air purifier,technology,HEPA (High Efficiency Particulate Air) Filter
The right air purifier can actually help by providing safe and clean air if certain pre-requisites are met

If you’ve bought an air purifier, chances are that you’ve either bought the wrong one or aren’t using it right. I know, pretty harsh, but true. Between the fact that most air purifier companies are selling you products by scaring you, selling devices with exaggerated features that you don’t need mixed in with the reality that 99 per cent people use their air purifiers wrong – your air purifier is pretty much useless. Now sit back, breathe in some more of that poisonous air and let me try and rectify the situation.

An air purifier is a simple device in itself. It’s got a fan that sucks in air and blows it out and has a filter(s) that cleans that air. There is absolutely nothing else to it. But within this simple action lies the essence of life and death for your lungs. We spend nearly 90 per cent of our time indoors and the air is more polluted than the outdoors. Thus the air purifier has to do a fantastic job to get clean air in your room. Most air purifiers are sold based on high sounding self-named technology, looks and number of filters while its efficiency lies elsewhere. Unfortunately, there is a bit of jargon and acronyms involved. Pay heed though as this really matters.


Ignore any company that sells you air purifiers giving seven- layer, nine-layer or even 11-layer filtration. What you need in India is just two or three filters.

HEPA (High Efficiency Particulate Air) Filter: Most will be rated to remove 99.97 per cent of particles that are 0.3 microns and larger. Check this. If the manufacturer doesn’t state this, don’t buy it.

Pre-Filter: These trap larger particles before they get to the main filter, thus extending the life and efficiency of the HEPA Filter. Best if this is a separate filter that can be removed and cleaned.

Carbon Filter: These have activated carbon within, thus removing odours and chemicals like cigarette smoke, formaldehyde, paint fumes and kitchen odours.

Some acronyms

In India, an air purifier with just two or three filters is enough

An air purifier’s job is to clean the air and make it pure. How long it takes to do that and how well it maintains it even if the door is opened once in a while – are determined by the following.

CADR stands for Clean Air Delivery Rate and this tells you the volume of filtered air that the device can blow out. This is critical as a higher CADR number is what you’re looking for.

Monitor the air purifier’s efficiency with an external AQI monitoring device kept on the opposite side of the room

ACH is Air Changes per Hour. Each Purifier comes with a room size rating. What’s important is how quickly can the purifier change all of the air in that given space per hour. ACH rating of six to eight is a must.

CFM is Cubic Feet per Minute and measures how many cubic feet of air move through the unit per minute. You need a higher CFM.

Wasting money

I’ve seen offices place air purifiers in open cabins. I’ve seen huge hospitals place little air purifiers in lobbies and I’ve seen schools put them in classrooms. Each of them is wasting money and lungs as an air purifier needs certain critical dos that must be adhered to.


You have to shut the door of the room for the air purifier to make any difference. It’s impossible in a classroom where the door opens multiple times or even in open cabins or large lobbies. Next, clean the pre-filter and replace the HEPA filter exactly at the time it’s specified. Place it in the most uncluttered area of the room so that it can suck in more air. Run it continuously when you’re in the room. Monitor its efficiency with an external AQI monitoring device kept on the opposite side of the room.

Very few brands of air purifiers specify all the things I’ve listed above. May I make an emotional statement. You’re selling a life-saving device. Suck up a little bit of that profit and put those ratings of your device in bold on the box. Our current lungs and our future generations will thank you for it.

Rajiv Makhni is managing editor, Technology, NDTV, and the anchor of Gadget Guru, Cell Guru and Newsnet 3

From HT Brunch, December 17, 2017

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First Published: Dec 16, 2017 21:09 IST