Breathe easy!

They used to say: Your home is your castle. Shut the door and shut out the world and its problems. Not anymore. Today, the world — and its polluted air — comes seeping in, through every crack and crevice.

Last month, Delhi had the dubious distinction of becoming the city with the worst air quality in the world.  But other Indian cities are not far behind;  many figures in the global Top Twenty of most polluted places:  Gwalior, Allahabad, Patna, Raipur, Ludhiana, Kanpur... Southern metros like Hyderabad, Bangalore and Chennai are only a whisker short of this name-n-shame list,  albeit in specific pockets.  The villain is usually fine particle pollution  -- called particulate matter (PM). Cities like Pune, Kolkata, Amritsar suffer from nitrogen dioxide pollution, caused mainly by vehicular emissions.

In all these cities,  this is no longer an outdoors-only problem.  Air quality even indoors is degrading alarmingly. The argument: "My grandparents lived to be 90 in this same home, without such fancy stuff", is longer be valid.   We are more prone than ever, to respiratory ailments and by 'we'  one means especially the very young and the old who are more vulnerable. If you live in an apartment or house that is on a busy road,  or near a  smoke emitting industry, chances are you are more in danger of the effects of air pollution.   An air purifier will provide definite relief and may prevent frequent visits to the clinic.

All air purifiers improve the air quality, some better than others.  Their basic function is to filter out the particulate matter for which they all use what is known as a HEPA --High Energy Particulate Arrester -- filter. This is usually classified as a PM 2.5 filter which means it can remove particles of dust, soot and smoke, larger than  2.5 micrometres in size. Just to give you an idea,  a human hair is 100 micrometres in thickness or 40 dust particles in a row.  These ultra-fine particles can go straight to the lung and can trigger chronic diseases such as asthma, bronchitis and other respiratory problems.  Even larger particles  up to   PM10 or ten micrometres pose a health concern because, in spite of the human body' own filtering mechanisms, they are small enough to be inhaled. Indoor Air Purifiers depending on the make,  also come with some other filtering mechanisms:   courser  filters to  take off  visible dust;  ultraviolet ray generators to kill some ( not all) germs; special filters to address  fungal spores and pollen which many people find allergic;  active carbon to absorb bad odours -- even  a  bit of Vitamin C to deodorize the air.

Thanks to the air quality crisis in north India this year, a  dozen brands of indoor air purifiers  are available all over India...  names like  Atlanta, Blue Star, Kent, Eureka Forbes, Honeywell, Moonbow,  Nirvana  Panasonic, Philips,  Samsung, Sharp, Xiaomi.... Typically such purifiers cost between Rs 15,000 and Rs 40,000 and are good for averagely sized apartments, covering  25 - 60  square meters. Each make has some special claim:  Philips touts its Aerasense technology which in addition to particles,  addresses allergy-sources like pet dander and dust mites.  Sharp says it is the first in the world to add a mosquito catcher.  Moonbow uses activated charcoal to capture gases and bad odour.  Xiaomi's Mi Air Purifier can be controlled with a mobile phone and has attracted buyers by being the first to sell for less than Rs 10,000.  New entrant Nirvana has offerings all across the price spectrum, from the Airgle AG600 costing nearly 1.35 lakhs to anti-viral 'Respokare' re-useable face masks for Rs 400 - Rs 1000.

Do indoor air purifiers work -- and if so how well?  The Energy Research Institute (TERI)  carried out a study earlier this year, using Sharp units in three different types of locations in Bangalore and Delhi, over a period of two months. Results showed that irrespective of the building type, the performance of the air purifiers improved with time. The maximum reduction in fine particles as well as harmful gases was observed when the air purifier runs for 90 minutes.  So clearly they do help clean the air.  Unless the environment in Indian cities improves sharply, we may  have to resign ourselves to increasingly cleaning the air we breathe,   even as we are used to cleaning the water we drink.  There is a new Enemy Within. We ignore it at our peril. 

— IndiaTechOnline