Stop making pollution indoors

Incense, mosquito coils, cooking smoke and heaters can make indoor air worse than outdoors. These are the free fixes.

A purifier works against everything that adds particles to the room, not only what leaks in from outside. Some everyday habits release large amounts of fine smoke right next to the people breathing it.

The biggest indoor sources

Source	What to do
Incense, dhoop, agarbatti, havan	Avoid indoors during the pollution season. If used for prayer, keep it brief, in a ventilated spot away from bedrooms, with the exhaust on.
Mosquito coils	Avoid. Burning coils release a lot of smoke. Use window mesh, bed nets or electric repellents instead.
Smoking (including bidis and hookah)	No smoking indoors, ever. It is the largest controllable source of indoor PM2.5.
Candles and oil lamps (diyas)	Keep to a minimum indoors. Use electric lights for décor.
Frying, tadka, grilling	Use an outdoor-vented exhaust, lids, and lower heat where possible. Keep bedroom doors closed while cooking.
Gas stoves	Use the exhaust and ventilate the kitchen. Gas burners also release nitrogen dioxide, which particle filters do not remove. Induction avoids burner emissions (the food itself still smokes).
Sweeping and dusting	Damp-mop and damp-dust instead of dry sweeping. A vacuum with a sealed HEPA filter is better than a broom.

Heating safely in winter

Never use charcoal, coal or wood (angithi, sigri) indoors. It releases carbon monoxide (CO), an odourless gas that can kill people in their sleep, plus heavy smoke.
Kerosene and gas room heaters also produce CO and need ventilation. Electric oil-filled radiators and fan heaters produce no combustion fumes.
Fit a carbon monoxide alarm if anything burns fuel in the home (gas geyser, stove, heater).

Festivals

Firecrackers around Diwali cause some of the sharpest spikes of the year. Keep windows shut, keep purifiers running in occupied rooms that evening and the next day, and keep sensitive family members indoors.