Filtered ventilation and passive purifiers: Decoding air quality for homes

The air quality is severe in most cities in North India. Very poor, if we get lucky on some days. Our cities are enveloped in dense smog, a deadly concoction of particulate matter, nitrogen dioxide, sulphur dioxide and other pollutants. The sunshine barely filters through. Burning sensation in the eyes and lungs betraying a heaviness with every breath outdoors. Little does a human body care about numbers that define air quality index (AQI). Unfortunately, the insides of our homes and workplaces aren’t shielded from reality of our outdoors.

The question many are asking, is it possible to pollution proof your home? Air purifiers provide a straightforward answer to this conundrum, something a greater number of citizens are trying to tackle. There is also a second method, which is filtered ventilation and these are customisable, often expensive solutions that run air from outside through a filter before circulating that indoors, which experts talk to HT about.

An air purifier, depending on a configuration you’ve purchased, will have a series of filters including a pre-filter for larger particles, a HEPA or high-efficiency particulate arrestance filter for smaller pollutants, and activated carbon for airborne bacteria and volatile compounds. The room’s air is pulled in by the fans, and it passes through these layers of filters which capture pollutants, particulate and allergens, before the cleaned air is blown back into the room.

“Of course, air purification is the solution. Absolutely, it is possible to pollution Proof Your Home to a 95% extent,” Barun Aggarwal, CEO and founder of air quality experts BreatheEasy Consultants, and author of How to Grow Fresh Air. He clarifies that when he references that figure of 95%, he’s factoring in the times when windows or doors in a home will open, or cleaning will take place. “At those times all bets off, especially when outdoor readings are as high as they are” he says.

Intensifying problem, and changing perceptions

Typically, there has been resistance towards air purifiers, but that perception is fast changing. “At Xiaomi, we’ve witnessed a 150% increase in sales for our Xiaomi Air Purifier Series 4 since October, reflecting the growing demand for Air Purifier category, particularly in highly polluted regions. We have observed consumers are gravitating towards health conscious buying that not only enhance air quality but also align with their fast paced lifestyles,” Anuj Sharma, Chief Marketing Officer at Xiaomi India, tells HT.

The company, which currently has a range of three air purifiers priced between ₹9,500 and ₹14,000, has partnerships with quick commerce platforms including Blinkit. At this time, e-commerce platforms Amazon and Flipkart, haven’t released their data indicating air purification shopping trends.

It is a case of choice aplenty for buyers. Popular air purifier brands in India include Dyson, Philips and Xiaomi, alongside premium solutions from IQAir and Airgle. On any online shopping website and also in physical stores, many more brands vie for attention, but they may not deliver best filter efficiency.

Pooja Baid, who is Chief Marketing Officer at Versuni India Home Solutions (formerly Philips Domestic Appliances) points out that while the purifier sales are indeed at their highest in Delhi NCR and other parts of North India, that trend isn’t restricted to this part of the country only.

“The air purifier market is witnessing significant growth this season, driven by deteriorating air quality across India. New pollution hotspots are emerging in regions like Maharashtra, Bihar, Odisha, and Rajasthan. This alarming trend has heightened consumer awareness about indoor air quality, transforming air purifiers into a necessity rather than a luxury,” she says.

According to Baid, consumers are increasingly opting for advanced models featuring HEPA filters, activated carbon layers, real-time AQI displays, and smart connectivity (that allows for monitoring and controls using a smartphone app). “The demand is no longer limited to metro cities, with Tier 2 and Tier 3 markets becoming important growth hubs. Families with children, elderly individuals, or those with respiratory or cardiac conditions are leading this shift,” she adds.

An understanding gap, and countering it

Still, many consumers question of these devices will do them any good, considering they spend enough time in the outdoor pollution.

“There’s a big understanding gap. It’s a cumulative effect when you’re breathing in pollution. The more pollutants go into the lungs, the blacker your lungs get, and they faster they reach a point of failure. Pollutants also go into the bloodstream and affect other organs. If you can avoid breathing pollution for seven or eight hours a day, you are giving those organs respite, making them stronger, versus reducing immunity,” points out Barun Aggarwal.

Jai Dhar Gupta, CEO of Nirvana Being, a clean air solutions business, illustrates how indoor air composition can be quite dangerous for health. “Indoor air is typically 10 times worse. All outdoor pollutants in ambient air are indoors too, with additional sources such as off-gassing from construction materials, gases and VOCs from housekeeping materials, oil-based particles, smoke from the kitchen, bio-contaminants if someone is unwell, and build up of carbon dioxide through natural process of breathing,” he points out.

The composition of an air purifier

Depending on how fine the sieves in a filter are, and the density of its final composition, most air-purifiers can catch airborne particles larger than or equal to 0.3 microns—microns being the standard unit for measuring air particles. Each micron is 1/25,400 of an inch. HEPA filters have ratings, with filters between H10 and H12 being ‘true HEPA’, while H13 and H14 are medical grade. The latter can capture airborne particles as small as 0.2 microns.

Xiaomi’s latest generation purifiers cost ₹9,999 onwards, while Philips’ updated 3200 Series, 4200 Series, and 900 Mini portfolio can be bought for ₹8,500 onwards. Most affordable consumer purifiers have H10 or H12 rated filters. Premium ones, such as the Dyson BIG+Quiet (around ₹66,000) has an H13 filter. All HEPA filters have a usable life, post which they must be replaced.

Companies are getting innovative with solutions

Nirvana Being’s latest generation MESP purifier, which HT has reviewed, replaces HEPA with a Micro-electrostatic Precipitator or MESP filter, reduces cost of filter replacement by making this filter washable. MESP is a honeycomb structure of metallic tubes that have an insulation coating generating electrical fields within the tubes – pollutants are charged particles and get pulled towards these tubes (eventually stuck). Periodically, wash this with running water.

HEPA filters are a composition of fibers, mostly polypropylene, borosilicate and fiberglass. They cannot be washed, only cleaned occasionally.

Indian company Airth along with IIT Kanpur and IISc Bangalore, has developed HEPA filters for split air-conditioning units too, with different configuration for enhanced filtration during higher pollution winter months. These are easy to install, and cost around ₹2,199 whilst converting your existing AC into an air purifier.

The IQAir Atem X, which Breathe Easy sells in India (that’s around ₹1,69,000) has evolved the traditional HEPA methodology further, to create the HyperHEPA HF filter. “The 3D multi-layer construction minimizes airflow resistance while maintaining exceptional filtration performance,” says the company.

What to keep in mind, and what to avoid

Breathe Easy’s Aggarwal points out the methodologies of passive and active air filtration, and why one needs to be “avoided like a plague”, as he puts it. “Active air filtration includes newer technology like air ionizers, ozonizers, photocatalytic oxidation and electrostatic precipitators. I don’t believe in those technologies, even though they are being sold fairly openly. There are enough negative byproducts that are produced for these technologies that can be harmful to human health,” he says.

The air purifiers we recommend, follow the method of passive filtration — this means running the air through a number of filters including HEPA and carbon, to trap and hold pollutants, thereby preventing them from being free in the breathing space.

It is important for an air purifier to be an ideal fit for the room size. Purifiers are sold with different cleaning capacity ratings, including CADR, or clean air delivery rate. A mistake many make is to lead the purchase decision by looking at the price tag. A smaller, and therefore more affordable purifier, may not be able to effectively clean the polluted air volume in a large room.

That problem gets compounded in more active rooms, such as a living room, where outside air too may stream in occasionally.

“Most Indian households have significant leakage of air. That can be from windows or doors opening regularly. Air Purifiers work most effective in closed environments,” points out P.K. Jain, Managing Director of Atlanta Healthcare, a leading air quality management company in the country working with hospitals and commercial establishments.

“Completely pollution-proofing your home might not be entirely feasible, but significantly reducing indoor pollutants is achievable. Air purifiers are a key part of this strategy, effectively removing dust, allergens, smoke, and other airborne particles. However, they work best when combined with other measures like sealing gaps, and maintaining a clean environment,” says Pooja Baid.

Air purifiers work in the room they are kept, and are not meant to be centralised systems indoors. If you keep one in the living room, it will not clean the air in the bedroom.

Is filtering outdoor air, a solution for indoors?

Atlanta Healthcare’s Jain points to an ideal approach that should work for most homes, is to create a positive pressure of purified air inside the house. On a morning when the AQI outside was hovering around 500 according to official numbers, Atlanta Healthcare’s Jain tells us his bedroom’s AQI reading was 2. “When I opened to bedroom door, it went up to 100 in 10 seconds,” he says. Within a few more seconds, the AQI reading in the room shot past 250.

Jain believes the key is to ensure the volume of purifier air emerging in a room is higher than in any adjoining indoor areas or the outdoors accessible through gaps or doors that are opened for passage. “Negative pressure will invite polluted air into the house. Close the rooms and purify,” is the simple advice. Similar air purification methods, though more precise and expensive, are traditionally used for patients with immunocompromised conditions.

Nirvana Being’s Jai Dhar Gupta explains what he believes is an ideal implementation. “A scientific solution, involves both filtered ventilation to mitigate CO2, VOCs, Gases, PM2.5 and create a positive pressure on the home, as well as filtration in your living areas as well through air purifiers or MESP filters on your duct-able AC units. A combination of filtered ventilation and filtration on recirculating units in each living area indoors is a sure shot way to achieve a health and safety compliance indoors,” he says.

Filtered ventilation will require some installation work at home, unlike a plug-and-power-on air purifier unit. These solutions can be costlier too, since they are often customized depending on physical layout.

Barun Aggarwal says most of us are focusing on what he calls “recirculation filtration”, amidst what he describes as “massive craziness that’s happening outside in terms of particulate matter because of a combination of stubble burning predominantly during this period, changes in wind direction and temperature inversion.”

Breathe Easy Labs, for example, has something called the IQAir In-Flow Ducting Kit, which costs around ₹55,000 and is compatible with all IQAir purifiers meant for indoor use in homes and commercial establishments. The idea is to install this ducting in a way (think of this as a mechanism similar to a chimney, except the direction is in reverse, which is inward) that the purifier pulls in outdoor air through this, runs that air through a series of filters and releases clean air into the room.

But these solutions aren’t light on the pocket, because of the additional parts that make this jigsaw. The special ducting kit will work with an IQAir HealthPro 100 (that’s around ₹1,37,000), a HealthPro 150 (that costs ₹1,42,500) or a HealthPro 250 (this flagship is priced at ₹1,59,000). Barun Aggarwal says they’ve installed this solution in more than 10,000 homes in recent months. He hopes awareness will help users breathe clean air indoors, whether it is with a simpler air purifier, or a more customized solution such as this.