But here’s the thing: when we talk of worsening air quality, we allude to outdoor or ambient air. Air purifiers, by scope and function, are meant to filter indoor air. Never mind the government’s Chaplinesque move to install Wayu (Wind Augmentation PurifYing Unit) devices across some Delhi intersections. Its capacity to purify air within a 500 square-metre radius means the megapolis would need as many Wayus as termites to a mound.

So, how bad is indoor or household pollution? Terrible, claim air purifier brands. And they’re not wrong. There’s no dearth of studies on indoor air, but since WHO is the gold standard, let’s focus there.

3.8 million people across the world die each year from diseases related to indoor pollution. India suffers an 11% proportional mortality rate from chronic respiratory diseases, with 70-89 deaths per 100,000 being attributed to household pollution. 59% of our population is primarily reliant on polluting fuels, or biomass.

“When indoors, there’s the danger of volatile organic compounds (VOCs), formaldehyde, and carcinogenic agents from cleaners and sprays. Indoor air is typically 5-10 times worse than ambient air pollution,” says Sudhir Pillai, GM of Honeywell India’s Homes division. Pillai is echoed by Philips India’s marketing director and business head Gulbahar Taurani, and BlueAir country head Arvind Chabra. The clarion call of indoor air pollution being worse than ambient pollution is a tie that binds competitors.

But here’s why fine print matters. WHO data for India points to an indoor air crisis in rural centres or among the urban poor – both of which aren’t target groups for an industry whose unit prices range from roughly Rs 8,000 to Rs 1,00,000-plus ($110 to $1371-plus).

The naysayers

“First, there are no guidelines for indoor air pollution. Which means there’s no quantification of acceptable levels of certain household pollutants,” says Dr Chirashree Ghosh, an aerobiologist and associate professor with the department of environmental studies, Delhi University.

What India has is the National Ambient Air Quality Standards (NAAQS), which lists acceptable concentrations and measurement methods for 12 pollutants (PM 2.5, PM 10, sulphur dioxide, nitrogen dioxide, ozone, lead, carbon monoxide, ammonia, benzene, benzo-pyrene, arsenic, and nickel). There are no parameters for measuring pollutants other than these, leave alone doing so in enclosed spaces.

Dr Ghosh’s 2014 pilot study on indoor air quality across Delhi’s economic zones does reveal, however, that questionable structural materials and increasing tendency to leave windows closed could be bigger contributors to urban indoor pollution than, say, a dusty carpet. This also explains sick building syndrome.

“There’s also no understanding of the implications of poor urban planning, least of all when it comes to respiratory issues,” she outlines. “In the macro picture, HEPA filters are temporary solutions at best.”

In March this year, news trickled in about the government spending Rs 36 lakh ($49,327) to install 140 air purifiers across seven agencies, including the PMO.

The Central Pollution Control Board (CPCB) wasn’t one of them.

“But you can’t say indoor pollution is worse than ambient pollution. Context matters. In the industrial belt from Dhanbad to Durgapur, for example, which do you think would be worse?”

Meanwhile Dr Virendra Singh, editor of the peer-reviewed medical journal Lung India, underlines the need for double-blind, placebo-controlled studies in the National Physical Laboratory to substantiate air purifier claims. Now, since India has no indoor air pollution parameters, there’s no regulatory body akin to the Bureau of Indian Standards (BIS), which other consumer goods adhere to. Multinational companies (MNCs) therefore brandish international certifications like the European Centre for Allergy Research Foundation (ECARF) or the Association of Home Appliance Manufacturers (AHAM) from the US. There’s no sure shot way to prove whether products tested abroad would be as effective in Indian conditions.

Number crunching

But none of this matters. Here’s why.

In December 2016 – when Honeywell India officially started selling air purifiers – 95% of its business came from Delhi-NCR. In under two years, this figure is now down to 75%, with Mumbai being an emerging driver alongside Bengaluru. And while Honeywell GM Sudhir Pillai doesn’t divulge unit sales figures, he points to as much as a threefold increase (year-on-year) in overall sales.

“The scientists there aren’t using air purifiers. Neither am I,” chuckles Dr SK Tyagi, a former CPCB member who serves on the board of the Indian Association for Air Pollution Control. Yes, he concedes, VOCs are a concern because air fresheners, deodorants, and cleaners that were once luxury items are no longer so, meaning respiratory tract irritants and the count of carcinogenic compounds may have spiked in urban homes.