Diwali air purifier guide: a night-of plan for cleaner indoor air

Diwali is diyas, sweets and the whole family under one roof. In many Indian cities it is also the night the air turns thick with firecracker smoke, and the start of weeks of winter smog.

You can't control what happens on the street, but you can control the air in one or two rooms of your home. This Diwali air purifier guide is a simple plan for before, during and after Diwali night: which room to protect, when to shut the windows, how to run your purifier, and how to tell whether it's working. At the end, we explain which Airnest purifier fits which room, sized in square feet.

Firecracker smoke indoors: why the air gets worse on Diwali night

Firecracker smoke is full of fine particles, measured as PM2.5. Outdoors, the numbers climb fast. On Diwali night in 2025, the monitoring station at Nehru Nagar in Delhi recorded PM2.5 of 1,763 µg/m³ around 10 pm (The Indian Express, citing CPCB and DPCC data), almost 30 times the national 24-hour limit of 60 µg/m³ (CPCB, National Ambient Air Quality Standards). Across the city, CPCB's daily bulletins show Delhi's 24-hour average AQI rising from 296 ("poor") the day before Diwali to 345 ("very poor") on Diwali day (CPCB AQI Bulletin, 19 Oct 2025; CPCB AQI Bulletin, 20 Oct 2025).

That smoke doesn't stay outside. The US EPA notes that particles found indoors include particles of outdoor origin that migrate indoors, and that indoor levels depend on outdoor levels, how much air leaks in, and the ventilation and filtration you use (US EPA, Indoor Particulate Matter). Open windows, gaps under doors and balcony doors left ajar all let it in.

The weather makes it worse. An analysis of CPCB data by the research group Climate Trends linked the 2025 spike to firecracker emissions combined with winds below one metre per second and temperature inversions that trap pollution near the ground (Business Standard, citing CPCB data). If you're not sure what the numbers on your AQI app mean, here's our guide to what AQI 300, 400 and 500 mean.

The whole plan on one page: before, during and after Diwali night.

Before Diwali night: prepare the house

• Check or replace your H13 HEPA filter. Clean the pre-filter. Replace the main filter if it's due, or if it looks grey and clogged.
• Choose your clean room. Usually the bedroom where you'll sleep. Ideally its windows and door close properly.
• Size the purifier to that room. Length × width in feet = sq ft. A 12 × 14 ft bedroom is 168 sq ft.

On Diwali night: windows shut, purifier on

• Close windows and doors early, before the crackers begin. A rolled towel helps with a gap under the door.
• Run the purifier on high for the first hour, then turn it down to a quieter setting for the night.
• Keep the clean-room door closed. Step in and out quickly.
• Don't add smoke inside that room. Light diyas and agarbatti in the puja area or another well-ventilated space.

After Diwali: while the pollution lingers

• Check the outdoor AQI before you air out the house. Don't open the windows first thing the next morning.
• Air out at the cleanest time of day. On poor to severe AQI days, ventilate between 12 pm and 4 pm if needed (MoHFW).
• Keep the purifier running in the room you use most.
• Wet-mop floors rather than sweeping, so settled dust isn't kicked back into the air.

Before Diwali: prepare for Diwali pollution

Check or replace your H13 HEPA filter

The filter does the cleaning, so check it before the busiest night of the year. Clean the pre-filter as your product manual describes, and look at the main filter. If it's due, or visibly grey and clogged, replace it now. Aura owners can get a genuine Aura replacement filter, with H13 HEPA media, a pre-filter and activated carbon.

Choose your "clean room"

You don't need to purify the whole house. Pick one room to keep as clean as possible on Diwali night. For most families that's the bedroom where you'll sleep, or the room where grandparents or children will spend the night. Ideally, its windows and door close properly.

Size the purifier to that room

Measure the room's length and width in feet and multiply them. A 12 × 14 ft bedroom is 168 sq ft. Then make sure your purifier is rated for at least that area. A purifier that's too small for the room will run all night without keeping up. Our room size and CADR guide walks you through it step by step.

On Diwali night: using an air purifier for Diwali smoke

1. Close windows and doors before the fireworks start

Shut the windows in your clean room in the early evening, before the crackers begin, not once you can already smell smoke. If there's a big gap under the door, a rolled towel helps.

2. Run the purifier on high for the first hour

Switch the purifier on as soon as the room is closed up and run it on its highest setting for the first hour. That clears the smoke that came in before you shut the windows. Then turn it down to a quieter setting so it can keep running while everyone sleeps.

3. Keep the clean-room door closed

Every time the door opens, air from the rest of the house comes in with it, so step in and out quickly.

4. Don't add smoke inside that room

Diyas and agarbatti are part of the evening, so light them in the puja area or another well-ventilated space rather than in the room you're keeping clean. The EPA lists burning candles among the indoor sources of particles (US EPA), and the Health Ministry advises avoiding incense sticks and mosquito coils in closed rooms (NCDC/MoHFW Health Advisory). Room fresheners and fragrance only add scent. They don't clean the air.

After Diwali: when the pollution lingers

Smoke from Diwali night often lingers, and in North India the smog usually stays for weeks. In 2025, Delhi's 24-hour average AQI was still 351 ("very poor") at 4 pm the day after Diwali, and it stayed "very poor" for two more days (353 and 305) before easing to "poor" (275) on 24 October (CPCB AQI Bulletin, 21 Oct 2025; 22 Oct; 23 Oct; 24 Oct).

• Check the outdoor AQI before you air the house. Don't throw the windows open first thing the next morning just because the fireworks have stopped.
• Air out at the cleanest time of day. On poor to severe AQI days, the Health Ministry advises keeping external doors and windows shut in the morning and late evening, and ventilating, if needed, between 12 pm and 4 pm (NCDC/MoHFW).
• Keep the purifier running in the room you use most, and wet-mop floors rather than sweeping so settled dust isn't kicked back into the air.

Which Diwali air purifier fits your room?

Once you have a plan, the right purifier is the one sized for your clean room. Both of our purifiers use an H13 HEPA filter that captures 99.95% of particles down to 0.3 microns.

Room	Pick	Coverage	Price
Bedroom, kids' room, study	Airnest Core	Up to 250 sq ft	From ₹3,699
Living room, large bedroom	Airnest Aura	Up to 390 sq ft	From ₹4,299
Any room: see what the air is doing	Airnest Smart AQI Monitor	Shows PM2.5, CO2, temperature and humidity	From ₹2,999

Pick by room size: the Core for most bedrooms, the Aura for larger rooms.

• For most bedrooms, choose the Airnest Core. A typical Indian bedroom of 120 to 200 sq ft sits comfortably within its 250 sq ft coverage, which makes it a natural fit for your Diwali clean room.
• For a living room or a large bedroom, choose the Airnest Aura. It covers rooms up to 390 sq ft, so it suits the room where the family gathers on Diwali evening.
• Not sure of your room size? The room size guide linked above explains how to measure it. You can also browse all Airnest air purifiers or read our bedroom air purifier checklist.

How do you know it's working?

You can't see PM2.5, so the only way to know whether your clean room is cleaner is to measure it. The Airnest Smart AQI Monitor shows PM2.5, CO2, temperature and humidity in real time, and sounds an alarm when readings cross its thresholds.

An indoor reading tells you whether closing up and running the purifier is making a difference.

On Diwali night, a monitor helps you answer practical questions:

• Did PM2.5 in the room come down after the first hour on high?
• Is smoke getting in under the door or through a window that doesn't seal well?
• The next day, is the air inside still better than outside, or is it time to air the house?

Keep the monitor in the clean room, away from the purifier's outlet, so it reads the room rather than the air coming straight out of the filter.

Frequently asked questions

Should I run an air purifier all night on Diwali?

Yes, if you can. Run it on its highest setting for the first hour after you close up the room, then switch to a quieter setting so it can keep running while you sleep. Keep the windows and the room door closed.

Should I keep windows closed during Diwali?

Yes. Close windows and doors before the fireworks start and keep them shut overnight. On poor to severe AQI days, the Health Ministry advises not opening external doors and windows in the morning and late evening, and ventilating, if needed, between 12 pm and 4 pm.

What size air purifier do I need for my bedroom?

Measure the room's length and width and multiply them to get the area in sq ft. Choose a purifier rated for at least that area. The Airnest Core covers rooms up to 250 sq ft, which suits most Indian bedrooms. For larger rooms up to 390 sq ft, choose the Airnest Aura.

Which air purifier is best for Diwali smoke in a bedroom?

Choose one sized for the room you'll sleep in, with an H13 HEPA filter. The Airnest Core covers bedrooms up to 250 sq ft, which suits most Indian bedrooms; for a larger bedroom or living room up to 390 sq ft, choose the Airnest Aura. Both use an H13 HEPA filter that captures 99.95% of particles down to 0.3 microns.

Is an air purifier useful after Diwali too?

Yes. Smoke from Diwali night often lingers, and in North India winter smog usually follows. Keep running the purifier in the room you use most, and check the outdoor AQI before you open windows.

Get your clean room ready this Diwali

A clean room for Diwali night comes down to closed windows, a closed door and a purifier that fits the room. For most bedrooms, that's the Airnest Core: an H13 HEPA filter (99.95%) and coverage up to 250 sq ft, from ₹3,699.

Buying from us: shipping is free on orders of ₹4,999 and above, and every order comes with 7-day returns: faulty items are returned free, and for change-of-mind returns you pay the return shipping. Adding the AQI Monitor to a Core (₹6,698 together) takes you past the free-shipping threshold.

Wishing you and your family a happy, bright and safe Diwali.

Sources

1. The Indian Express (21 October 2025), "Worst Diwali night air in Delhi in at least 3 years as firecrackers burst almost non-stop" (citing CPCB and DPCC data: Nehru Nagar PM2.5 of 1,763 µg/m³ around 10 pm on Diwali night): https://indianexpress.com/article/cities/delhi/worst-diwali-night-air-delhi-firecrackers-burst-non-stop-10318394/
2. Business Standard (21 October 2025), "Diwali night fireworks send PM2.5 levels skyrocketing in Delhi-NCR" (Climate Trends analysis citing CPCB data: winds below 1 m/s and temperature inversion): https://www.business-standard.com/india-news/delhi-air-quality-post-diwali-2025-very-poor-pm25-five-year-high-125102100749_1.html
3. CPCB, National Ambient Air Quality Standards (2009 Gazette notification): PM2.5 24-hour limit of 60 µg/m³: https://cpcb.gov.in/uploads/National_Ambient_Air_Quality_Standards.pdf
4. CPCB daily AQI bulletins (Delhi, 24-hour average at 4 pm): 19 Oct 2025, 296 Poor: https://cpcb.gov.in/upload/Downloads/AQI_Bulletin_20251019.pdf ; 20 Oct 2025 (Diwali), 345 Very Poor: https://cpcb.gov.in/upload/Downloads/AQI_Bulletin_20251020.pdf ; 21 Oct 2025, 351 Very Poor: https://cpcb.gov.in/upload/Downloads/AQI_Bulletin_20251021.pdf ; 22 Oct 2025, 353 Very Poor: https://cpcb.gov.in/upload/Downloads/AQI_Bulletin_20251022.pdf ; 23 Oct 2025, 305 Very Poor: https://cpcb.gov.in/upload/Downloads/AQI_Bulletin_20251023.pdf ; 24 Oct 2025, 275 Poor: https://cpcb.gov.in/upload/Downloads/AQI_Bulletin_20251024.pdf
5. US EPA, Indoor Particulate Matter (outdoor particles migrating indoors; candles as an indoor source): https://www.epa.gov/indoor-air-quality-iaq/indoor-particulate-matter
6. NCDC / MoHFW, NPCCHH Health Advisory on Air Pollution (2022) (window timing; incense and mosquito coils in closed rooms; wet mopping): https://ncdc.mohfw.gov.in/uploads/pdf/air4.pdf
7. Airnest Core product page: https://airnesthomes.com/products/airnest-core
8. Airnest Aura product page: https://airnesthomes.com/products/airnest-aura-air-purifier
9. Airnest Smart AQI Monitor product page: https://airnesthomes.com/products/airnest-air-quality-monitor-co2-pm25
10. Airnest Aura replacement filter page: https://airnesthomes.com/products/airnest-aura-replacement-filter