Tech talk: Breathe easy this winter

Air purifiers are becoming a necessity in most Indian cities, especially in homes with children and senior citizens

An air purifier essentially filters out PM2.5 - particles that are 2.5 microns in size – using a HEPA (High Efficiency Particulate Air) filter. (IStockphoto)

The air quality in most cities in India is poor, especially during winter. More and more people are now buying air purifiers, especially those with children and senior citizens at home.

They're becoming more of a necessity and as with water purifiers, might become the new norm in upper middle-class households in the country soon.

How air purifiers work

An air purifier essentially filters out PM2.5 - particles that are 2.5 microns in size - using a HEPA (High Efficiency Particulate Air) filter. Some cheaper models instead use 'HEPA-type' filters which have limited effectiveness. Note that some ionizers and humidifiers also claim to clean the air around you, but they cannot be considered air purifiers.

As you go up the range, many purifiers have additional filters, such as a pre-filter to capture larger dust particles and activated carbon filters to capture allergens that may get through the HEPA filter.

The HEPA filters have a life that depends on how polluted the air around you is and hence is a recurring expense. A pre-filter significantly improves the life of the HEPA filters and while the pre-filters are easily washable, HEPA filters cannot be washed and need to be replaced. HEPA filters that don't have a pre-filter last around six months and those that have pre-filters, around 12-15 months.

The purifier you buy must be the right fit for the room you wish to use it in. You need to match the size of your room with the coverage area specified by the manufacturer. Like air-conditioners and room heaters, air purifiers too are a 'per room' appliance. You'll get clean air only in the room which has your purifier and not across your house. So, depending on your family size, you may want to invest in more than one.

Obsolete benchmarks

With the growing appreciation for air purifiers in India, several brands have jumped into the fray to cash in on the market. However, in absence of any recent regulatory requirements and benchmarks regarding air purifier certifications in India, the performance claims are often unsubstantiated.

Most air purifiers gauge their performance using a laboratory test method called 'Clean Air Delivery Rate'. However, the CADR test was developed over three decades ago and does not represent real home conditions.

Some purifiers, like Dyson, prefer to validate their portfolio with what is called the POLAR test. The POLAR test lab is based on a larger room size and assesses the ability of machines to remove harmful particles and gases, the uniformity of the cleaning performance delivered around the whole room, and airflow projection.

Recommended picks

While you can access the AQI (air quality index) of the area you live in with apps like AirVisual and AQI India, you can also use a pollution monitor, like Honeywell Indoor Air Quality Monitor and Kaiterra Laser Egg, to help you monitor the air quality, PM2.5 content, and temperature and humidity in your room.

When it comes to air purifiers, the market is crowded with a slew of options available at every price point.

Xiaomi offers pretty good options at the entry level. The Mi Air Purifier 2s is a great buy and includes smart home integration and mobile app connectivity. They also recently launched a cheaper Mi Air Purifier 2C which misses out on all smart and sophisticated features but delivers on the clean air promise like its more expensive sibling.

Amongst the traditional electronics brands, Philips offers a wide portfolio of air purifiers depending on your budget with better feature set as you go up the price ladder.

If you are on a liberal budget, you can consider options from Sharp or Dyson. The star of the latter's portfolio is the Dyson Pure Hot + Cool that simultaneously purifies and heats the room eliminating the need to use a separate room heater.

There's also Dyson Pure Cool Me which is a unique personal air purifier and fan that projects cool, filtered air and is best suited for use on desks or side tables.

If you have kids or seniors in the family that move around the city often, you can also consider using an air-purifier in the car. The two best options for clean air on-the-go are the Philips GoPure and the Honeywell Move Pure Car Air Purifier.