Keep the indoors pollution-free with the right air purifier for your space

Before buying, check your room size, filters type, ease of use and maintenance cost

The winter is a difficult time for citizens in the national capital, especially those with respiratory issues, as the region's air quality plunges to levels that have the potential to trigger a health crisis. And with the pandemic still around, the need to keep viral and bacterial infections, and allergens at bay becomes critical. Brian Hu, senior engineer, Dyson says, "While air pollution levels vary through the year, they peak at this time in India owing to changes in the weather and temperature, as well as seasonal activities." All these factors have led to a spike in the demand for air purifiers in the past, and if you are in the market to buy air purifiers, there are a few things to need to know before buying.

Who should buy: To understand pollution, you need to check the air quality index (AQI) level. An AQI of 0-50 is good, 50-100 is moderately good, and 101-150 is unhealthy and anything above this is hazardous. There are websites that report the AQI of your city and even neighbourhood, but the truth is that it isn't just an outdoor problem. Hu says, "While poorer air quality is a concern now, outdoor air is only part of the problem. Every day we can breathe in up to 9,000 litres of air and could be taking in more pollutants indoors as we are spending up to 90 per cent of our time behind closed doors." Clearly, if you live in an area with an AQI level above 100, you should consider buying an air purifier, but most experts say the pollution indoor is over 100 already. If you are allergic to pollen, tobacco smoke, grains, dust, mites, mould, and pet hair, consider getting one. Those with asthma or a weak immune system, or those living near a construction site, should buy one too.

There are a few things to keep in mind while buying, though.

Room Size and CADR: An air purifier is not a one-size-fit all device. Rachit Arora, director, MIE says, "The first step to filtering out air purifiers is figuring out how much space you want your device to clean. For instance, one could have a small 100 sq ft room or a large 800 sq ft living room. Keeping in mind the exact dimensions of the room while buying a purifier is crucial.." Small devices aren't effective in large living spaces, while larger, heavy-duty air purifiers may be overkill in small rooms.  

CADR: Hu says, "Some air purifier and humidifier manufacturers test performance with a lab test called ‘Clean Air Delivery Rate’ (CADR), in which the air quality is measured with only one sensor.' It is an important parameter to know how much clean air the purifier can pump out for a room. 

Dyson follows a testing method called POLAR for its purifiers, which it claims is superior to the CADR score followed by the industry. Companies mention the ideal room size for air purifier models. Note, that the higher the CADR of an air purifier, the faster it will clean the air. The CADR should ideally be two-thirds of the room size.

Air change rate: Simply put, this shows the number of purification cycles the purifier completes in an hour. Again, a higher number indicates greater machine efficiency in purifying air.

Filter Types: Filters are the most important criteria for selecting an air purifier. Different purifiers have different purification mechanisms, such as HEPA filtration, Ionic filtration, Carbon filtration, and Photocatalytic filtration (See Box). Many air purifiers come with a pre-filter, which has the first layer of filter fitted ahead of the main filter to remove large particles of dust from the air. HEPA filters can remove 99.9 per cent of all the particles. Activated carbon/charcoal filters help absorb odours and gases, and neutralise smoke, chemicals, and food smell. "Consumers need to check if the purifier is efficient enough to remove small suspended particles, viruses, and bacteria. Our purifiers remove 99.97 per cent indoor air pollutants as tiny as 0.003 microns--the smallest of small particles--smaller than PM2.5. Our purifiers also remove 99.9 per cent of various viruses and bacteria,” says Dipanjan Chakraborty, marketing director, Philips Domestic Appliances. PM2.5 is a particulate matter 2.5 micrometers or less in diameter. It is able to travel deep into the respiratory tract and reach the lungs.

Features: After choosing the type and size of air purifier you need, consider whether you'd like any special feature.

Some features in the market include air quality indicators that give real-time updates on the quality of your air. Some indicators are light-based, others aree colour-based. Some come with remote controls too. Abhishek Jain, founder, bijlibachao.com says, "Filters are more important than features. A good combination of HEPA and an activated carbon filter is a must. You need this to remove particulate matter, bacteria, virus and chemical compounds, odours and gases."  

Robos at work: These machines are not very portable. Robot purifiers, which are a combination of vacuum cleaner, wet mop, and air purifier, have emerged as an option you might want to consider. “An air purifier is static and can only clean the air in one room unless you move it physically. Robotic purifiers use self-navigation to go from one room to another. Air purifiers can help clear up particulate matter. However for virus, fungus, and allergens there is no alternative to vaccuming,” says Saksham Karwal, executive director, Milagrow Humantech. These come with an app that will show which parts of the house have been covered. These robot purifiers come equipped with HEPA-12 filters.

Maintenance cost: In air purifiers, the key type of maintenance is replacement of air filters. Jain says, "Electricity cost isn't that big a deal. If you have a device that comes with a dehumidifier, the power consumption increases to around 200 watts." Portable home purifiers have a wattage rating of 50-70 watts. HEPA filters last about a year depending on use, while activated carbon filters typically last six months. Pre-filters usually last three months, but washable ones last longer. Others use heat or ultraviolet light to purify your air and kill germs and allergens, and don't need replacement filters. It would be best that you figure out the cost of replacement filters beforehand.

Be mindful of the claims made by the brands and should look out for test certificates and reports which back them. You may also want to look at how much noise the model produces.

Types of filters 

• Pre-Filters: Eliminate large particles like pet hair
• HEPA: Remove 99.9% of all the particles, which can be as small as 0.3 microns
• Activated carbon/charcoal filters help in absorbing odors and gases
• Antibacterial and Germicidal Filters help to eradicate harmful bacteria and germs
• UV filters minimise risk of air-borne infections
• Photocatalytic Oxidation (PCO) filter breaks down chemicals during the filtration process
• Charged Media Filters combine a particle along with an electrostatic charge filter to filter particles as small as 0.1 microns

Table: Indicative price list of some air purifiers available in the market

Model	Price (Rs)
Coway Professional Air Purifier, Special Green Anti-Virus True HEPA Filter (Coway AirMega 150 (AP-1019C)	20,700
Philips AC1215/20 Air purifier, removes 99.97% airborne pollutants with 4-stage filtration	12,995
Mi Air Purifier 3 with True HEPA Filter and Smart App Connectivity	9,999
Philips High Efficiency Air Purifier AC2887, with Vitashield Intelligent Purification	23,995
Honeywell Air Touch V2 Air Purifier with H13 HEPA Filter, Activated Carbon filter and Pre-Filter	7,999
Sharp Air Purifier for Homes & Offices | Dual Purification - ACTIVE (Plasmacluster Technology) & PASSIVE FILTERS (True HEPA H14+Carbon+Pre-Filter	9,999
Dyson Pure Cool Link Tower (White/Silver) - TP03	24,900

Notes:

Source: Listing by Bijlibachoa.com, exept Dyson;

Pricing: Company Websites except Honeywell and Sharp (from Amazon.com)