Air Purifiers, Masks and Plants: What Actually Helps During Smog

An honest hierarchy for smog season

Every November, NCR households spend real money on pollution defences, and much of it lands on things that cannot work. Before any purchase, hold the hierarchy in mind: first reduce exposure, by timing outdoor hours around the AQI and making no smoke indoors; second, filter the air of the room you sleep in; third, protect the breathing zone outdoors with a respirator that seals. Everything that genuinely helps fits one of these three shelves, and everything else, ionisers, a few potted plants, herbal room sprays, sells comfort rather than clean air. The sections below take the shelf items one by one.

HEPA purifiers: real physics, real limits

A true HEPA filter is a dense mat of fibres that captures fine particles as air is forced through, big particles by collision, the finest by their own zigzag motion into the fibres, and a good unit removes the vast majority of PM2.5 from the air it processes. The limits are practical: it cleans only the air that passes through it, so match the machine's clean-air delivery rate, the CADR figure on the box, to your room's size, and accept that one unit cleans one closed room, not a whole open-plan house. A purifier in a room with open windows is a fan with expenses.

Where to put it and how to run it

Give the purifier to the bedroom, because the hours you can most realistically spend in filtered air are the seven or eight you sleep, and a child's or elder's bedroom outranks the drawing room where guests sit. Run it continuously through the smog months with the door and windows closed, on auto or medium rather than off-and-on bursts, since particle levels rebound within an hour of stopping. The filter is the machine: a saturated HEPA cleans nothing, so change it on schedule, and treat a unit whose replacement filters are unavailable as no purchase at all.

Masks: the seal is the technology

An N95 or FFP2 respirator filters fine particles through layers of charged fibres that attract and trap them, but the filtration figure applies only to air that actually passes through the material. Air, like water, takes the easiest path, and on a loosely worn mask that path is the gap at the nose or cheeks, which is why a pinched nose-clip, snug cheeks and no fogging of spectacles matter more than any number printed on the packet. Surgical masks leak generously around the edges and cloth masks barely filter fine particles at all; both have uses against droplets, neither is smog equipment.

Plants: pleasant, but not purifiers

The idea that a few money plants or snake plants scrub indoor air descends from a spacecraft experiment in sealed chambers, and it does not survive household arithmetic: at room scale, the particle and gas removal of a handful of pots is negligible against ordinary ventilation, and you would need a room packed wall-to-wall with foliage to rival one small purifier. Keep plants for what they honestly give, greenery, humidity, and a better mood, and let no seller convince you they replace filtration. Overwatered pots in a closed winter room can even add mould spores to the air.

Ionisers, ozone machines and other gadgets to skip

Ionisers charge particles so they stick to walls and surfaces, which drops the meter reading while redecorating your room with the dust you meant to remove, and some emit ozone as a by-product. Machines sold outright as ozone purifiers deserve a plain warning: ozone is itself a lung irritant that worsens asthma, and no home should run one in occupied rooms. Fragrance sprays and camphor mask smells without touching particles. If a device does not physically pass air through a filter you can hold, replace and see darken with use, be sceptical of what it claims to remove.

A smog-day routine that puts it together

On a severe morning: check the AQI before the milk boils; shift the walk to afternoon or indoors; children to school in well-fitted N95s if they tolerate them, windows of the car or auto closed; purifier running in the bedroom all day, door shut; no agarbatti, coil or indoor smoke, exhaust fan on for every tadka; brief ventilation in the afternoon dip; saline nasal rinse for the congested; inhalers in pockets for the asthmatic. And watch the family for wheeze, night cough, breathlessness on stairs or rising reliever use, any of which moves the matter from shopping to the clinic.