When the AQI crosses 300, the air outside is “very poor” on India’s national scale, and above 400 it’s “severe”, a level that affects even healthy people. The most useful things you can do at home are to keep outdoor air out while the reading is high, stop adding smoke and dust indoors, and move exercise inside, while watching for symptoms that need a doctor.
None of this needs expensive gear. Most of it is about what you close, what you stop burning and how you clean.
What “very poor” and “severe” actually mean
India’s National Air Quality Index, run by the Central Pollution Control Board (CPCB), has six bands. This is the scale and the health note for each band, as published by state pollution boards such as Jammu and Kashmir’s:
| AQI | Category | Possible health impact |
|---|---|---|
| 0 to 50 | Good | Minimal impact |
| 51 to 100 | Satisfactory | Minor breathing discomfort to sensitive people |
| 101 to 200 | Moderate | Breathing discomfort to people with lung disease, asthma and heart disease |
| 201 to 300 | Poor | Breathing discomfort to most people on prolonged exposure |
| 301 to 400 | Very poor | Respiratory illness on prolonged exposure |
| 401 to 500 | Severe | Affects healthy people and seriously impacts those with existing diseases |
One of the pollutants that pushes the index up is fine particulate matter (PM2.5). The World Health Organization says these particles cause heart and lung disease and cancers. Of the deaths linked to outdoor air pollution in 2019, about 68% were from heart disease and stroke, 14% from COPD, 14% from lower respiratory infections and 4% from lung cancer.
Check your local reading on CPCB’s Sameer app or website before deciding whether to open windows or go out. The number can change a lot within the same day.
Who is most at risk
Everyone breathes the same air, but some people feel it sooner and harder. Air quality agencies such as the Bay Area Air Quality Management District list these groups as most sensitive to fine particles:
- People with heart disease or lung disease, including asthma and COPD
- Older adults
- Children
- Pregnant women and newborns
- People with conditions such as diabetes or obesity
If someone at home has asthma, now is the time to check they have their reliever inhaler, that it isn’t empty, and that they know their action plan. Our overview of asthma symptoms and precautions covers the basics.
Close up the house, then air it out when the reading drops
The US Environmental Protection Agency (EPA) advice for heavy particle pollution from smoke applies well to Indian smog:
- Keep windows and doors closed while the outdoor AQI is high.
- If your air conditioner has a fresh-air setting, switch it to recirculate.
- Pick one room where the family spends most time and keep that one as clean as possible.
Sealing the house shut for days isn’t the goal, though. Cooking, breathing and bathing all build up indoor pollution and moisture. EPA’s advice is that when outdoor air improves, even briefly, you should air out the home by opening windows and running kitchen and bathroom exhaust fans.
So when should you open up? Watch the live AQI, not the clock. A 2025 study of global PM2.5 monitoring data found fine particles often peak just after sunrise, fall through the day to a low in the late afternoon, then climb again in the evening and stay high overnight. Local patterns vary, so treat that as a rough guide and open windows for a short spell when your own reading is at its lowest.
Cut the smoke you make indoors
On a bad-air day, the indoor sources you control matter even more. EPA lists these activities as ones that add fine particles inside:
- Frying or broiling food
- Burning candles or incense (agarbatti and dhoop count)
- Smoking or vaping
- Vacuuming without a HEPA filter
Practical swaps for an Indian kitchen: steam, boil or pressure-cook more on high-AQI days and save the tadka and deep-frying for cleaner days. Run your chimney or exhaust fan every time you cook, and keep the kitchen door shut while you do.
Fuel matters too. The WHO’s household air pollution fact sheet says cooking with wood, crop waste, dung, coal or kerosene causes an estimated 2.9 million deaths a year worldwide, and women and children bear most of the burden because they spend the most time near the fire. LPG, electricity, biogas and solar are the cleaner options it lists. If anyone at home still uses a chulha or angithi for cooking or warmth, the smoggiest weeks are a good time to switch, even temporarily.
And please don’t smoke indoors, or let guests do it, when the air outside is already in the red.
Clean with a wet cloth, not a broom
Dry sweeping and dusting send settled particles straight back into the air you’re breathing. EPA advises against dry sweeping and suggests misting hard surfaces and then wet mopping instead.
A simple routine for high-AQI weeks:
- Wet mop floors daily rather than using a jhadu
- Wipe window sills, ledges and fan blades with a damp cloth
- Skip the vacuum unless it has a HEPA filter
- Shake out doormats and rugs outside only when the AQI dips
Do indoor plants clean the air?
Not in any way that matters on a smoggy day. The idea comes from small sealed-chamber experiments. When researchers at Drexel University reviewed 12 of these studies, they calculated that you’d need somewhere between 10 and 1,000 plants per square metre of floor to match the cleaning effect of the normal air exchange in a building. That analysis was about gases called volatile organic compounds and didn’t look at fine particles like PM2.5 at all, so it gives no support to the idea that a few pots of money plant or snake plant can clear smog from a room.
Keep your plants because you like them. Just don’t count on them in place of closed windows and wet cleaning.
Air purifiers, briefly
A portable air purifier can help in the one room where you spend most time, especially a bedroom. EPA suggests running it there as often as you can on a high setting and choosing a model that doesn’t produce ozone. It works best with windows and doors closed. We’ll cover sizing, filters and running costs in a separate article on air purifiers.
When to exercise, and when to skip it
Exercise makes you breathe faster and deeper, which pulls more particles into your lungs. The Bay Area agency’s advice during extreme particle pollution is to keep activity levels low and avoid anything that makes you breathe faster or more deeply.
For AQI above 300, that means:
- Move your walk, run or yoga indoors, and keep the intensity lighter than usual
- Don’t assume an early-morning walk is safer; check the live reading first
- Older adults and people with heart or lung disease should be the most cautious
Masks for outdoor trips are a topic of their own, and we’ll look at them in detail in tomorrow’s article.
When to see a doctor
Mild irritation (scratchy throat, watery eyes, a dry cough) is common on bad-air days. These signs are not mild. Based on NHS guidance on breathlessness, call 112 or go to the emergency department straight away if someone:
- Has severe difficulty breathing, is gasping or can’t get words out
- Has a tight or heavy chest, or pain spreading to the arms, back, neck or jaw
- Has lips or skin turning very pale, blue or grey
- Suddenly becomes confused
See a doctor the same day if breathlessness is worse than usual for you, you’re coughing up blood, or you notice palpitations. Chest pain on a smoggy day shouldn’t be brushed off as gas; our guide on telling gas pain from a heart attack explains why.
Frequently asked questions
Is AQI 300 dangerous for healthy adults?
At 301 to 400 (“very poor”), CPCB’s scale warns of respiratory illness with prolonged exposure. Above 400 (“severe”), it says even healthy people are affected. Cut long or strenuous time outdoors, and keep exercise indoors and light.
Should I keep windows closed all day?
Keep them closed while the reading is high, then air the house out for a short spell when the AQI drops, running kitchen and bathroom exhaust fans to clear indoor build-up.
Does a money plant or snake plant clean indoor air?
Not meaningfully. A review of the lab studies found you’d need 10 to 1,000 plants per square metre to match normal ventilation.
Can I do my morning walk if the AQI is above 300?
It’s better to exercise indoors at a lighter intensity. Fine particle levels are often high around sunrise, so check the live reading before stepping out.
Do children need extra care during severe pollution?
Yes. Children are among the most sensitive groups. Keep their outdoor play short on very poor and severe days, and watch for wheezing or fast breathing.
This article is for general information and is not a substitute for advice from a doctor. If you have symptoms or a health condition, please consult a qualified healthcare professional.