Breathing easy: Is an expensive air purifier necessarily more effective?

With the onset of winter bringing its usual pall of pollution-related gloom over the skies in North India, the conversation in Delhi, the second-most polluted city in the world, returns to the question of how to tackle pollution, indoors and outdoors.

Over the past two years, this concern has resulted in a thriving market for air purifiers in the national capital.

“The market is worth around anything between Rs 600 crores to Rs 700 crores in India,” said Jay Kannaiyan, co-founder of Smart Air purifiers. “[It] has shown 40% growth last year with more than half of its sales having taken place in Delhi-NCR."

Kannaiyan’s company projects itself as an affordable option in a confusing market where air purifiers can be bought for as little as Rs 15,000 and as much as Rs 80,000 depending on brand, quality and spin.

While several experts and doctors believe that air pollution can only be combated through policy level changes, and that alternatives like air purifiers are an ineffective solution for what is a very serious public health problem, others believe that the use of purifiers can at least mitigate the negative effects of breathing severely polluted air till long-term efforts to combat air pollution show results.

For instance, two major pollutants, PM (particulate matter) 2.5 and PM 10 – like dust, soot and pollen – can cause serious health problems in the long-term.

PM 2.5 is particularly dangerous pollutant because it is so tiny. Measuring less than 2.5 microns across – 30 times smaller than the average width of a human hair – it can enter the bloodstream and settle in the lungs, which, in the long term, can lead to cancer, cardiovascular and respiratory diseases. This pollutant is also to blame for much of the haze that blankets North India, especially in the winter when cool, heavier air mixes with these particles and stays suspended over the city, lowering visibility.

The World Health Organisation suggests that average PM 2.5 levels should not be more than 10 microgram per cubic metre in a year. Indian standards, which are not as strict, put the yearly threshold at 40 microgram per cubic metre. However, Delhi's average in the most recent July-November period was more than four times that, and 13 times higher than the WHO prescribed safety limit.

The promise of air purifiers

Going by their advertisements, leading air purifiers in the market claim to protect users from up to 99.7% pollutants – including particulate matter measuring 0.1 microns across, and a range of viruses – with the help of High-Efficiency Particulate Arrestance technology, widely known as HEPA.

HEPA filters were invented in United States in the early 1940s. These filters work by forcing air through a fine mesh made of thin fibres of glass to trap harmful pollutants like PM 2.5 and PM 10.

They are graded either on a numeric basis like HEPA-11, HEPA-12 and so on till HEPA-18 – the higher number denoting increased efficiency, or on the basis of types like HEPA type-A, HEPA type-B and so on, each of which have distinct specifications.

However, the HEPA filter in the fanciest air purifier will need to be replaced regularly. According to Kannaiyan, the life of a HEPA-13 filter – the most used filter – in Delhi is anything between two and four months. Replacements do not come cheap with leading brands charging Rs 4,000 to Rs 6,000 for each replacement.

“There are several brands that claim that their filters can last up to two years, which is impossible in case of a city like Delhi or Beijing,” said Kannaiyan. “Their research was conducted years ago and that too in European countries, where pollution levels are anyway low.”

Ankur Chawla, director (sales and marketing) of Crusaders Technologies, a leading player in the air purifier industry in India, added that a HEPA filter was not the only filter an efficient air purifier should have.

He said that it was important for an air purifier to have several layers of filters, each for a different purpose, including filtration of coarse dust, smoke, toxic gases and viruses. A pre-filter, for instance, removes bigger particles like hair and dust, reducing the burden on the HEPA filter. Similarly, an activated carbon filter removes gases such sulphur dioxide, nitrogen oxide and hydrogen sulphide (the source of the pungent smells one gets near large drains).

Said Chawla: “It is surprising that some leading brands, which try to capitalise so much on the HEPA technology, do not even feel the necessity of a pre-filter, thus exposing the sensitive HEPA to all sort of large and small pollutants."

But additional filters could increase the cost of an air purifier, which is possibly why the cost of air purifiers vary so greatly.

Elaborating on the importance of multiple layer of filters, Vijay Kannan, the India head of Blueair, a leading Swedish air purifier brand that launched in India in 2014, said that certain air purifier models are expensive because they have multiple filters.

“With three filters, even the basic model of our product eliminates pollutants down to 0.01 microns at a rate of five air-change per hour,” said Kannan. “This means the machine takes 12 minutes to complete one full cycle of transforming polluted air into fresh air.”

He suggested that the best way to use an air purifier is to keep it switched on round the clock, like a refrigerator, adding that an ideal model consumed minimum electricity. “With this, a person will get access to fresh air as soon as he or she enters home and at least for the period spent indoors.”

Paying for gimmicks?

However, Kannaiyan suggested that some expensive air purifiers are just gimmicky and should not actually cost that much.

“This thriving market of unreasonably expensive air purifiers largely capitalises on the fear of the various health threats posed by air pollution and lack of awareness among public on the same,” he said.

Kannaiyan said that to be effective, an air purifier needed a HEPA filter, a pre-filter for larger particulate matter, and an optional activated carbon filter.

Explaining why he thought air purifiers should not be expensive, Kannaiyan said that an ordinary HEPA-13 plate cost around Rs 1,299, a pre-filter cost about Rs 140 while an optional activated carbon filter cost a little more than an HEPA filter.

A “lack of awareness” was therefore to blame for the trend of people assuming that inexpensive air purifiers are ineffective, said Kannaiyan, adding that it was these people who opted for more expensive air purifiers.

“The same perception was there in Beijing [one of the most polluted cities in the world] too, but things changed over the past two years," he said. "With time, things are expected to change here too as people are now exposed to a lot of debate on the issue.”

‘Find long-term solution’

Polash Mukerjee, Research Associate in the Clean Air and Sustainable Mobility unit of the Centre for Science and Environment, echoed Kannaiyan’s views on the rapid growth of the air purifier market. “The fear of pollution has been utilised for economic gains and has successfully ended up creating a thriving market for the commodity,” said Mukerjee.

Mukerjee said that air purifiers were “a quick fix solution, like band-aid on a deep wound” and called for changes at the policy level as the only way to fight pollution.

He also flagged the class divide regarding access to clean air.

“Is clean air not something which everyone should have equal access to?” asked Mukerjee. “An air purifier is a rich man’s commodity...It is high time that we look forward to effective measures at both macro and even individual levels.”

Mukerjee added that the efficiency of an air purifier also depended on how airtight the space it is operated in was. “But spending too much time inside a sealed room, which lacks oxygen, leads to fatigue and other health issues,” he said.

Dr SP Byotra, senior consultant and chairman of the Department of Medicine at Delhi’s Sir Gangaram Hospital, was of the view that air purifiers were not that effective.

“Unless a person decides to spend all 24 hours near an air purifier, which is nearly impossible, it does not help much,” said Byotra. “A certain quantity of a pollutant like PM 2.5 gets settled deep in the lungs of an individual as he is exposed to the polluted outdoor air. After that, spending few hours in a room with an air purifier turns out to be ineffective.”