How to Reduce Indoor Air Pollution at Home in Delhi NCR

Updated October 22, 2026

Every October the same pattern returns to Delhi NCR: the Air Quality Index climbs, the Graded Response Action Plan (GRAP) kicks in, and households start asking what they can actually do indoors. You cannot change the air outside, but you can limit how much gets in and how quickly it is cleaned. This guide sets out practical steps to reduce indoor air pollution at home, from sealing and filtration to layout, kitchens, balconies and the plants-versus-purifiers question, using official guidance rather than marketing claims.

First, understand the numbers you will see

India’s National Air Quality Index, published by the Central Pollution Control Board (CPCB), sorts readings into six bands. These are the bands the SAMEER app, news reports and GRAP orders use.

AQI	CPCB category	GRAP stage (Delhi AQI)
0–50	Good	None
51–100	Satisfactory	None
101–200	Moderate	None
201–300	Poor	Stage I
301–400	Very Poor	Stage II
401–450	Severe	Stage III
Above 450	Severe+	Stage IV

The Commission for Air Quality Management (CAQM) revised the GRAP schedule in November 2025, moving several measures one stage earlier so that curbs start sooner. The current schedule on the CAQM website carries a revision date of 29 September 2026 and keeps the same four AQI bands. It also says a stage can be invoked in advance, based on forecasts, before Delhi’s AQI actually reaches that level. Because the plan is revised most years, check the CAQM website for the stage in force rather than relying on last winter’s rules.

For perspective, the World Health Organization’s 2021 air quality guidelines set PM2.5 levels of 5 µg/m³ as an annual mean and 15 µg/m³ as a 24-hour mean. WHO says 99% of the world’s population lived in places that did not meet its guideline levels in 2019. The realistic aim at home is lower exposure, not zero.

The three-step rule: source control, ventilation, filtration

The US Environmental Protection Agency (EPA) puts the priorities in a clear order. The most effective steps are to reduce or remove pollution sources and to ventilate with clean outdoor air. Filtration is a useful supplement, but EPA says it does not replace the other two, and no air cleaner removes every pollutant.

In NCR’s winter the outdoor air is often the problem, so in practice this means ventilating in short bursts when the AQI is lowest.

Sealing: stop the leaks before you buy a machine

A purifier fighting a leaky room is working against a constant inflow. Sealing is cheap and should come first. Walk each room with the windows shut and look for daylight or draughts at these points:

Window frames: sliding aluminium and uPVC windows often have worn brush seals. Replacing them, or adding self-adhesive weatherstrips, cuts the gap through which dust enters.
Door bottoms: a door sweep or draught stopper on the main door and the balcony door makes a visible difference to dust on floors.
Split AC and chimney pipe holes: the hole drilled for the AC pipe or kitchen chimney duct is frequently larger than the pipe. Fill the gap with a suitable sealant.
Exhaust fans: bathroom and kitchen fans with no back-draught shutter let outside air in when switched off. A fan with a gravity or louvred shutter helps.

Sealing has limits. A tightly closed home builds up moisture, cooking smells and other indoor pollutants, so you still need planned ventilation, covered below. And do not seal in a way that makes it hard to get out in an emergency; EPA’s advice on clean rooms makes the same point.

HEPA, CADR and MERV in plain terms

HEPA

HEPA stands for high efficiency particulate air. According to EPA, a true HEPA filter can in theory remove at least 99.97% of particles at 0.3 microns, which is the hardest size to catch; larger and smaller particles are trapped even more efficiently.

CADR

Clean air delivery rate (CADR) tells you how much filtered air a purifier delivers, usually measured at its highest speed. EPA advises picking a unit whose CADR suits the room, and using the tobacco-smoke CADR when you care about fine particles such as PM2.5, because smoke represents the smallest particles. Indian product listings often quote CADR in cubic metres per hour (m³/h); one cubic foot per minute (cfm) is about 1.7 m³/h.

MERV

MERV ratings apply to filters in central heating, ventilation and air-conditioning (HVAC) systems, such as ducted ACs in larger villas and some premium apartments. EPA recommends at least MERV 13, or the highest your system’s fan and filter slot can handle. A MERV 13 filter captures at least 50% of particles between 0.3 and 1 micron. EPA also notes that central systems filter only while the fan runs, so a ducted AC that cycles off is not filtering continuously.

Worked example: sizing a purifier for your rooms

EPA’s sizing chart works out to roughly 0.65 cfm of CADR per square foot of floor, assuming an 8-foot ceiling. Many NCR apartments have ceilings closer to 10 feet, and EPA says higher ceilings need a higher CADR. A simple adjustment is to scale by ceiling height.

Room	Floor area	EPA minimum CADR (8 ft ceiling)	Adjusted for 10 ft ceiling	In m³/h (approx.)
Bedroom, 12 ft × 14 ft	168 sq ft	109 cfm	137 cfm	232 m³/h
Living-dining, 15 ft × 20 ft	300 sq ft	195 cfm	244 cfm	414 m³/h
Open living + kitchen, 400 sq ft	400 sq ft	260 cfm	325 cfm	552 m³/h

How the bedroom figure is worked out: 168 × 0.65 = 109 cfm. Multiply by 10 ÷ 8 for the taller ceiling and you get about 137 cfm, or 137 × 1.7 ≈ 232 m³/h. That flow cleans a volume equal to the whole room roughly five times an hour.

CADR is measured at full speed, which is usually too noisy for sleeping, so a unit rated above the minimum lets you run it quietly and still meet the target. For open-plan spaces, EPA says to size for the whole area served, or use more than one unit.

Purifiers versus plants: what the evidence says

The idea that houseplants clean indoor air traces back to a 1989 NASA experiment. That work was done in small sealed chambers, often a cubic metre or less, with a single chemical injected and tracked over hours or days. It was never meant to describe a ventilated home.

A 2019 review by Drexel University researchers Bryan Cummings and Michael Waring, published in the Journal of Exposure Science and Environmental Epidemiology, looked at about a dozen studies across 30 years. They estimated it would take between 100 and 1,000 plants per square metre of floor to match the air cleaning provided by normal building ventilation. Plants are pleasant, but not a pollution control strategy.

Portable HEPA cleaners have stronger support. EPA says several studies found small improvements in cardiovascular and respiratory health markers, and some found improvements in allergy or asthma symptoms, though the gains are not always large or noticeable. If anyone at home has a health condition, take advice from a doctor rather than relying on a product claim.

One more caution: EPA advises avoiding air cleaners that deliberately produce ozone, a lung irritant. Ionisers, electrostatic precipitators, plasma units and some UV devices can emit ozone. Prefer plain mechanical HEPA filtration, with an activated carbon stage if you also want to tackle odours and some gases.

Comparing your options

Measure	What it tackles	Upfront cost	Running cost	Evidence
Sealing gaps (weatherstrips, door sweeps, sealant)	Outdoor dust and smoke leaking in	Low	Very low	Supported by EPA clean-room guidance
Portable HEPA purifier sized by CADR	Fine particles in one room	Medium	Electricity plus filters	Strong for particles (EPA)
MERV 13 filter in ducted AC	Particles across the home while fan runs	Low to medium	Filter changes, possibly more fan power	Recommended by EPA if the system can take it
Kitchen chimney with clean filters, ducted outside	Cooking smoke and grease	Medium	Filter cleaning	CAQM citizen charter advises regular cleaning
Activated carbon filter	Odours and some gases	Medium	Carbon replacement	EPA: works when there is plenty of carbon; no common rating system
Houseplants	Very little measurable effect on indoor air	Low	Low	Weak (Cummings and Waring, 2019)

Running-cost example. Running costs depend on your purifier’s wattage, your tariff slab and the price of replacement filters for that exact model, so do this sum with your own numbers. As an illustration only: a unit drawing 40 watts at a quiet speed, run 12 hours a day for 150 days of the smog season, uses 0.04 × 12 × 150 = 72 units. At an assumed ₹8 per unit, that is about ₹576 for the season. Filter replacement is often the bigger cost, so check the filter price and replacement interval before you buy the machine.

Kitchen ventilation: the pollution you make yourself

Cooking is one of the biggest indoor sources, and in winter, when windows stay shut, its smoke lingers. WHO’s work on household air pollution stresses clean fuels such as LPG, natural gas and electricity over solid fuels; most NCR apartments already use piped gas or LPG, which is the right starting point.

Use a chimney or exhaust that vents outside, and switch it on before you start cooking, not after the smoke builds.
Clean chimney filters on schedule. CAQM’s GRAP citizen charter specifically asks households to do this.
Keep the kitchen door shut while frying or tempering so that smoke does not spread to bedrooms where the purifier is working.
Avoid incense, candles and mosquito coils in rooms you are trying to keep clean. EPA lists these, along with frying and aerosol sprays, as activities to avoid in a clean room.

Note the trade-off: a strong kitchen exhaust pulls air out, and replacement air comes in through every gap in the flat. EPA advises using exhaust fans only for short periods in a room you are keeping clean for this reason.

Layout choices that help

If you are buying or renovating, a few design decisions make winters easier.

Create one clean room. EPA’s approach for smoke events is to pick a room, often a bedroom with an attached bathroom, keep it closed, avoid polluting activities in it and run a properly sized purifier. In NCR this is usually the main bedroom, where people spend 7 to 9 hours a night.
Separate the kitchen. A closed or semi-closed kitchen keeps cooking smoke away from living areas. Open kitchens need a stronger chimney and a purifier sized for the combined area.
Think about which side faces the road. When viewing flats, notice whether bedrooms overlook a busy arterial road, a construction site or open ground.
Check window quality. Well-fitted windows with good seals do more over the years than any single gadget. Ask about the window system and the gaps around AC pipe sleeves at handover.

If you are comparing homes, our locality guides for Noida and Gurugram describe the surrounding roads and development activity, which helps you judge nearby dust sources. You can browse listings across the region on the ADiHomes projects page.

Using balconies in smog season

Balconies are an asset for most of the year, but from late October they become the main path for dust into a flat. Some sensible habits:

Keep the balcony door shut on Poor, Very Poor and Severe days, and use the door sweep you fitted.
Open up for airing when the AQI is lower. Check the SAMEER app, as the CAQM schedule itself suggests.
At Stage IV, CAQM’s citizen charter advises limiting non-essential outdoor activity, and asks children, pregnant women, the elderly and people with chronic heart or lung conditions to stay indoors as much as possible. Balcony exercise and long sit-outs can wait.
If you glaze a balcony, check your society’s and the authority’s rules first, as enclosures may need approval.

Time renovations around GRAP

Home improvement work can itself pollute, and it can be stopped. The GRAP citizen charter asks people to avoid dust-generating construction work from October to January. At Stage III the schedule restricts, among other things, painting, polishing and varnishing, plastering, and cutting or fixing tiles and stone, with exceptions only for minor indoor repairs and maintenance. If you plan a fit-out, schedule the dusty work for spring or summer, and let any new paint or polish air out before winter sets in.

The bottom line

None of this makes a flat immune to NCR’s winter smog. But sealing leaks, filtering the rooms you use most and controlling what you generate indoors are the steps that official guidance supports, and they are within reach of most households.

Frequently asked questions

What is the most effective way to reduce indoor air pollution at home in Delhi NCR?

US EPA guidance ranks source control and ventilation with clean outdoor air first, with filtration as a supplement. In NCR's smog season that means sealing gaps, avoiding indoor smoke sources and running a properly sized HEPA purifier in the rooms you use most.

How do I choose the right purifier size for a room?

EPA's chart works out to roughly 0.65 cfm of CADR per square foot for an 8-foot ceiling, so a 168 sq ft bedroom needs about 109 cfm. Increase this for higher ceilings, and use the smoke CADR for fine particles.

Do indoor plants clean the air?

Not in any meaningful way. A 2019 review by Cummings and Waring estimated that 100 to 1,000 plants per square metre would be needed to match normal building ventilation.

What AQI levels trigger each GRAP stage?

Under CAQM's schedule, Stage I applies at Delhi AQI 201–300, Stage II at 301–400, Stage III at 401–450 and Stage IV above 450. Stages can be invoked in advance based on forecasts, so check the CAQM website for the stage in force.

What MERV rating should I use in a ducted AC?

EPA recommends at least MERV 13, or as high as your system's fan and filter slot can accommodate. A technician can confirm what your system can handle.

Are ioniser air purifiers safe?

EPA advises avoiding air cleaners that intentionally produce ozone, which is a lung irritant. Ionisers, electrostatic precipitators and some other electronic cleaners can emit ozone, so mechanical HEPA filtration is the safer choice.

Can I do home renovation work during the smog season?

The GRAP citizen charter asks people to avoid dust-generating construction work from October to January. At Stage III, painting, polishing, plastering and tile cutting are restricted except for minor indoor repairs and maintenance.

Sources

Updated 20 October 2026. This article is general information, not legal or financial advice; check current rules and project details before you decide.