Air purifier buying guide: how to choose the right air purifier

With air quality worsening with every passing day, there’s a new home appliance that’s almost become mandatory for anyone concerned about health – the air purifier. Available in a wide range of sizes (and at various price points), air purifiers are an excellent way of making the air inside your home or office safe to breathe. Ask around – many of your friends might already be using air purifiers, and you’ll also find them in places like offices and cafes. But when it comes to choosing an air purifer, there’s a lot of jargon like PM 2.5, CADR, HEPA filters and other terms, which might be confusing to the average buyer. To help you understand these and more, we’ve come up with this buying guide to air purifiers: We hope this will make your purchasing decision a lot easier. 

Also read: 5 things to consider when buying an air purifier

Who needs an air purifier?

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Indian cities have some of the worst air quality in the world. In fact, India ranks third on the 2018 World Air Quality report (released by IQAir AirVisual and Greenpeace). 8 of the 11 worst-affected cities were in India – Gurgaon, Ghaziabad, Faridabad, Bhiwandi, Noida, Patna, Lucknow and Delhi. Air pollution usually spikes in winter, with crop fires, climatic conditions, vehicular emissions, construction sites, and even firecrackers exacerbating the situation. Delhi’s air quality has, on many occasions, crossed 999 for PM 2.5 pollutants) – the maximum reading in many air quality instruments. On some occasions, air quality meters at the US Embassy in Delhi have seen the air quality cross even 1200.

 But while these are just extreme instances, it’s not like the air is clean even on ‘good’ days. India’s National Air Quality Index which lays out safe limits for different types of pollutants, includes a limit of 30 for PM 2.5 and 20 for PM 10, a limit which is met, if you’re lucky, on one or two days a year.

The harmful effects of air pollution

Air pollution kills. Contrary to what some people believe, you cannot build ‘resistance’ or ‘immunity’ to air pollution. This silent killer, as some term it, results in a whopping 1.2 million deaths a year in India. South Asians (including Indians) lose 2 years and 6 months of life expectancy thanks to dirty air. But that’s not the only issue. Even on a day-to-day basis, air pollution impacts the quality of our lives. From asthma attacks and breathlessness, to poor performance in schools and at work, to having to curtail outdoor activities, we can’t escape air pollution.

Different types of air pollution

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While we usually assume air pollution to be an outdoor-only issue, this couldn’t be further from the truth. Not only does external air (and pollutants) make its way indoors, but our homes and offices are also sources of pollution that are as harmful as the pollutants that come from outdoor sources.

Outdoor air pollutants

That thick smog you see in the air probably consists of particulate matter from a variety of sources – vehicular exhaust, coal power plants, dust carried by wind, stone, cement and other dust, or chemicals from construction sites, wood fires, burning plastic, crop fires, industries… the list goes on.

Indoor air pollutants

Our homes are also sources of pollution. Damp conditions can lead to growth of toxic mold which can have serious consequences. Meanwhile, inefficient exhaust systems lead to pollution from activities such as cooking. Even pets such as cats and dogs shed hair, which is especially bothersome to those with allergies. The list doesn’t stop here – incense, fragrances, and even paint / polish on walls and furniture, all contain pollutants that can have serious consequences for vulnerable people such as children, the elderly, and the ill.

Different type of pollutants

We’ve spoken of the sources of pollution but what about the pollution itself? What exactly is it that makes air dirty?

PM2.5 / PM10 particulates: Particulate matter such as that you’d find in dust, soot, smoke (under 2.5 and 10 microns) has been linked to asthma, breathing trouble, heart disease, strokes, and other health problems. PM2.5 is considered particularly dangerous as the particles are small enough to enter the bloodstream via the lungs.

NO2: Vehicles are the main source of Nitrogen Dioxide, which has been linked to asthma, wheezing, and other breathing issues.

SO2: Caused by burning of fossil fuels such as coal and diesel, Sulphur Dioxide causes acid rain, atmospheric haze and creates breathing issues.

CO: Carbon Monoxide can even kill in higher concentrations, and is created when fuels such as wood, charcoal, coal and other organic fuels are burnt.

O3: Ozone is a serious air pollutant created when certain other pollutants react with sunlight and is very harmful to our lungs.  

NH3: Ammonia is created from agricultural and industrial activities and is considered an aggravating factor for increased particulate matter pollution.

Pb: Lead, which can cause brain damage, has been completely removed from sources such as petrol and paints, but is often created by industrial activity.

VOCs: Volatile organic compounds, also found indoors, comes from a variety of sources – from industrial emissions, to something as ‘harmless’ as art supplies and paints. These have been cited as a factor for ailments ranging from eye irritation to organ damage and cancer. Examples of some common VOCs are toulene and formaldehyde.

Radon:This gas is created by the decay of naturally occurring radioactive elements in soil, and bricks and is considered a factor in lung cancer. Usually only an issue indoors.

Mold: Poorly maintained homes and buildings in areas with heavy rainfall are prone to mold growth, which can cause allergic reactions, asthma and lung damage.

Pet hair: As anyone with pets knows, many animals shed their hair, more so in hot months – this can lead to asthma in some people.

Pollen: Pollen from plants can aggravate allergies in susceptible individuals.

What air purifier is best for you?

There are a wide variety of air purification technologies on the market, and most purifiers use a combination of these.

Pre-filters: The most basic, pre-filters in air purifiers are similar to those found in air conditioners. These are normally washable and reusable, and filter out the biggest particles (such as dust or sand) that may clog finer filters.  

Ionizing purification: These use high voltage current to ionise (negatively charge) air particles, which attach to dust particles that eventually settle down on indoor surfaces. Some ionizers may have internal dust collection surfaces as well. Purifiers that use just this technique are often the most affordable. However, they don’t clean the most serious pollutants, and may also generate ozone, which may worsen conditions.

HEPA filters: HEPA filters are the main weapon of air purifiers. These use sheets containing fibres that trap particulates. HEPA filter efficiencies are set by standards organisations and may differ from country to country. Still, as a yardstick, assume HEPA filters can clean over 99 percent of particulate matter smaller than 0.3 microns. 

Activated Carbon: Activated carbon works wonders in filtering out VOCs (see above) and may reduce the impact of unwelcome smells.

UV: Ultraviolet light kills a wide range of pathogens and are sometimes found in air purifiers – the air passes in front of a UV lamp, which should remove many illness-causing bacteria and viruses. Similar in nature to the UV lamps you’ll see in water purifiers. 

What size air purifier do I need?

As with air conditioners, air purifiers come in a range of capacities. And just as air conditioner capacities are measured in tons, air purifiers have their own measure of capacity: Clean Air Delivery Rate (CADR), which is the air flow (Cubic Feet per Minute, or CFM) of clean air. Larger rooms will do better with a higher CADR, as you’ll get to the ‘clean’ stage faster.

One rule of thumb – as recommended by the Association of Home Appliance Manufacturers is to get an air purifier with a CADR value that’s at least two-thirds the room’s area.

Running costs of an  air purifier

Another factor you need to consider is the costs of consumables: Pre-filters can be washed but might need changing eventually, UV lamps can burn out, activated carbon and HEPA filters can’t be reused but need replacement. On an average you’ll be changing your carbon and HEPA filters once in six months, so do factor that into account. Some brands use composite filters, where all three types of filters are combined in one, while others let you change individual filters. Easy availability of consumables is another factor – pick a brand that lets you purchase filters online, or has a store or service centre near your home or office. 

And finally, there’s the cost of keeping an air purifier running constantly. You’ll find most residential air purifiers range from 30W to 50W, which is about the same as an incandescent bulb.

Other features to consider

You would think effective air purification is the only parameter to judge air purifiers from different brands. But there are other features that can really elevate the ownership experience. Keep an eye out for these:

Filter alerts: Most models warn you with beeps / alarms when their filters are getting clogged, but some models might even show you (via an in-built display or through an app) how many days of usage you have left. This can really help by letting you order new filters just in time.

Air Quality Indicators: Some air purifiers do not include any air quality measurement. Others show you a ‘good / bad / hazardous’ level using LEDs. However, we’d recommend that you pick a model that shows you the PM 2.5 count, either via an app or through a display.

Noise levels: Some brands tout the silent operation of their models. Keep in mind manufacturer noise ratings may be for the quietest modes – such as a night mode. However, in general, you’ll be happier in the long run with a quieter model, as they just blend seamlessly into the background.

Smart features: If air conditioners can be smart, so can air purifiers. Smart features run the whole gamut here, from something as basic as an ‘auto’ mode that adjusts fan speed based on air quality, to something as convenient as app-based operation over Wi-Fi, offering features such as remote operation, time-based rules, current air quality levels, and estimated filter life.

We hope this buying guide will help you choose the right air purifier for your needs. To make it easier, we’ve also compiled a list of the top air purifiers under Rs 10,000, under Rs 20,000 and under Rs 40,000. Also check out our roundups of the top air purifiers from Sharp and Honeywell.