Assess the quality of filtration system
Advanced air purifiers that use a combination of purification systems are ideal
Seventy three-year-old Ravi Meattle, a resident of central Delhi, has been taking great care to ensure his air purifier is working well this winter. He gets its filters vacuum-cleaned every week and changes the filter every six months, even if it sets him back by ~6,000-8,000. But that is an investment in health for Meattle, who has chronic respiratory problems. Aradhana Ghosh, a mother of two young children, has installed air purifiers in both the bedrooms in her house and does not let her children go out to play. “Nowadays you don’t just feel pollution, but you can see, smell, and taste it too. We often wonder if we should migrate to escape this gas chamber,” says the 42-year-old. Abi Stringer, design engineer, research design and development, Dyson, shares how in January 2019 Bangkok declared an emergency when the Air Quality Index (AQI) hit 179. In London, where she resides, people start buying air purifiers as soon as the reading hits 50 or 60. She says it is unbelievable that the AQI has to cross 500 in Delhi before the authorities raise an alarm. After Diwali, several areas of Delhi recorded an AQI of 999, beyond which a reading is not possible. Such unprecedented levels of pollution have led to a spike in the sales of air purifiers in recent years. Says Mahesh Gupta, chairman and managing director, Kent RO,
“In the past four years, we have seen a surge in the demand for air purifiers in Delhi during the smog situation.”
The market is replete with choices. Prices range from ~6,000 to over ~1 lakh. Some of the major players are Philips, Sharp, Blueair, Eureka Forbes, Dyson, Honeywell, LG Electronics, Kent R O, Atlanta Healthcare, Panasonic, Crusaders Technologies, and Daikin Air Conditioning.
Filtration system holds the key: The filtration system is the core of a purifier. Several types are available. One is where ultraviolet light uses electromagnetic radiation to destroy bacteria, viruses and mold. However, this variant does not remove dust, allergens or air particles. In another, activated carbon filters react chemically with pollutants to clear smoke, odours and gases, but they are unable to filter out very fine particles. In a third variant, air ionisers work by sending out a stream of charged ions to attract dust and allergens. However, they can produce ozone, a respiratory irritant, as a by-product. Then you have high-efficiency particulate air (HEPA) purifiers, which trap pollutants and fine particles across a range of sizes. They do not, however, remove volatile organic compounds.
The best purifiers combine HEPA filters with activated carbon, enabling them to remove both particulate matter and volatile organic compounds. Advanced air purifiers use a combination of purification systems and a set of filters. They have a four-stage filtration process — primary filter, carbon, HEPA and ionizer — to make the air 100 per cent clean and pure.
When selecting an air purifier, look for what it targets — normally the culprits are PM2.5, PM10, volatile organic compounds and nitrogen oxide. The most commonly measured size is 2.5 microns and particles of this size are referred to as PM2.5. Most filters tend to capture this. Some purifiers can capture particles as small as PM0.1, which impact not just the lungs but also enter the bloodstream.
Accurate sensor is essential: Most entry-level purifiers have a basic LED indicator system for air quality. Avoid these. The newer models come with a digital display that shows the actual air quality level in your room. They make it easy to decide when to run the purifier at the highest level and when to turn it down.
Take room size into account: A 600 square-foot room will require 40 watts at top speed, says a Dyson spokesperson. But even the most powerful purifier may not work even if the room size is small, if the walls are thin, or the windows are susceptible to leakage. “If your room measures 150 sq. ft, get an air purifier that indicates a rating that is at or just above this number. A 200 or 250 sq. ft rating would be just as efficient as one that measures 150 sq. ft exactly,” says a spokesperson from Kent.
Rahul Aeron, Assistant Vp-sales, Desiccant Rotors International Pvt Ltd (DRI), Pahwa group, says that since the acceptable levels of PM2.5 as per UN guidelines is 25 g/m3, 24-hour mean, but let’s say in Delhi today PM2.5 is 500, then you need to stop 475 particles. Then the purifier has to work at 90-95 per cent efficiency level.
Pay heed to maintenance: The filter should be cleaned regularly and replaced every 6-12 months, depending upon usage. It may cost anything between ~4,000 and ~8,000. Filters of most air purifiers can be vacuum cleaned.