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Delhi NCR Air Pollution Survival Guide — How to read AQI, choose an air purifier, prepare for winter smog season

By ARAZIA India Desk10 min read

Delhi Air Pollution — Severe winter smog over Delhi as seen by NASA satellite — NASA/GSFC/LaRC/JPL, MISR Team (Public domain, Wikimedia Commons)

After spending my first winter in Delhi NCR, I realized that the real difficulty of living in India was not the heat.airI truly feel this. One morning in late October, when the outside of the window becomes hazy, your throat feels raw, and the AQI number on your phone app exceeds 300 or 400 — the period from then until February of the following year is what residents of Delhi, Gurgaon, and Noida refer to as ‘smog season.’ Even if you have experienced 'very bad' fine dust in Korea, winter in Delhi requires a different level of preparation.

Fortunately, this seasonAround the same time every year, in the same patternIt's coming. In other words, it is a problem that can be easily managed if you know when it gets worse and when it gets better, what to buy in advance and how to change your lifestyle. In fact, Korean families who have survived several winters in the region have become ingrained in the routine of checking equipment and adjusting their daily schedules by looking at the AQI app starting in September.

In this article, we will explain why Delhi smog repeats every winter, how to read the Indian AQI rating and a confirmation app, the impact of the government's step-by-step regulation (GRAP) on daily life, criteria for choosing an air purifier and mask, and a pre-season preparation checklist — organized in order based on actual living experience.

01Why does Delhi smog repeat every winter? Understanding the season calendar first

Air pollution in Delhi NCR is a constant throughout the year, but there is a distinct reason why it becomes particularly severe in winter. When the monsoon ends in October, rain no longer washes away the dust, and around the same time,Stubble burning after harvest in Punjab and HaryanaSmoke is blown into Delhi by the wind. hereDiwali firecrackers, and winter-specificAtmospheric inversion layer (a phenomenon in which cold air spreads on the surface, preventing pollutants from escaping upward)As wind and wind overlap, a structure is created in which vehicle exhaust gases, construction dust, and industrial emissions are trapped above the city.

period	air quality trends
March~June	Heat, dust and sandstorms — ranging between ‘average’ and ‘poor’
July~September	Monsoon rain washes away the dustCleanest time of the year
october	End of monsoon + start of stubble burning — rapid deterioration
November	Diwali firecrackers + burning peak + atmospheric stagnation —worst of the year
December~February	High concentrations persist due to low temperatures and inversion layer, mixed with thick fog.

Speaking from experience, what is considered the 'worst fine dust' day in Korea is closer to an 'okay day' in Delhi's winter. So winter in Delhi is not about ‘avoiding bad days’ approach;Set bad air as the default and manage indoor air quality and outdoor habits.Access is required. Please note that during December and January, smog and fog overlap, making early morning visibility extremely poor, so please factor this into your itinerary plans as flight delays departing from Delhi Airport are common during this period.

Delhi winter smog season — A winter morning with thick fog and fine dust mixed in — From December to January, smog and fog overlap in Delhi, making early morning visibility extremely poor and flight delays frequent. · Vishwasgaur (CC BY-SA 4.0, Wikimedia Commons)

02How to read AQI — Indian rating scale and verification app

AQI (Air Quality Index) is an indicator that converts the concentration of various pollutants such as PM2.5 (ultrafine dust), PM10, and ozone into a single number. India has regulations set by the Central Pollution Control Board (CPCB).6 levels on a 0-500 scaleUse .

AQI section	India CPCB Rating	life tips
0~50	Good	A rare day in Delhi's winter - Doing outdoor activities and ventilation
51~100	Satisfactory (good)	Normal life possible
101~200	Moderate	People with respiratory sensitivities should avoid outdoor activities for long periods of time.
201~300	Poor	Stop exercising outdoors, wear a mask when going out
301~400	Very Poor	Minimize going out, always operate air purifier
401~500	Severe	Sealing windows, switching to living indoors — this actually happens often during the winter.

There is one important catch here.India's CPCB-type AQI and the US EPA-type AQI have different calculation formulas, so even for the same air, numbers are displayed differently in each app.For example, IQAir apps use the American style, while Indian government apps use the Indian style. You need to get into the habit of checking ‘what standard the grade is for’ rather than the number itself. The fact that Air Korea's 'very poor' (PM2.5 76 µg/m³ or higher) level is routinely exceeded in Delhi's winters also helps in calibrating the senses.

Verification channels used by actual residents

SAMEER app— CPCB Official App. Check the official AQI from stations across India
SAFAR— Air Quality Forecast Service under the Indian Ministry of Earth Sciences. Provides forecast for large cities such as Delhi
IQAir AirVisual App— American AQI standards, time zone forecasts and maps are intuitive
aqicn.org (Global Air Quality Index Project)— Check the figures for each observatory directly on the web

There is a large variation in numerical values even within the same city depending on the location of the observation station.Bookmark the observatory closest to your homeA realistic way to use it is to cross-check two or more apps.

03GRAP — The impact of government regulations on pollution levels on my life

Delhi NCR has a step-by-step response system that is automatically activated when the AQI exceeds a certain level.Graded Response Action Plan (GRAP)There is this. It is implemented every winter by the NCR Air Quality Management Committee (CAQM), and as the level increases, measures that directly affect daily life, such as construction suspension and vehicle operation restrictions, increase. When you see expressions like ‘GRAP Stage III activated’ in the news, you can get a feel for it using the table below.

step	Trigger criteria (AQI)	Major influences on life
Stage I	Poor (201~300)	Basic measures such as cracking down on old vehicles and suppressing dust at construction sites
Stage II	Very Poor (301~400)	Restrictions on the use of diesel generators, etc. — may affect apartment power backup
Stage III	Severe (401~450)	Suspension of non-essential construction work, restrictions on some vehicle operations, and adjustments to classes for lower grades.
Stage IV	Severe+ (above 450)	Highest level measures, including restrictions on truck entry, suspension of in-person school attendance, and conversion to online classes.

From the perspective of an actual resident, there are three things that are particularly noticeable. first,Closing and online transition of children's schools— This has been repeated every winter in recent years, so please check the school's emergency notification channels (email, app) in advance. Second,Diesel Generator Regulations— In the event of a power outage, the Apartment Society's backup power operation may be limited. Third,vehicle operation restrictions— There may be discussions about restrictions on age and fuel standards or the odd-even system, which becomes a variable in vehicle use plans. Detailed measures are adjusted each year, so please check CAQM/CPCB notices and local news for the latest information during the season.

04Air Purifier Selection Guide — CADR Calculation, HEPA Rating, Filter Management

The core of Delhi NCR winter survival gear is definitely an air purifier. In conclusion,‘One appropriate capacity unit per room’ is the correct answer rather than ‘one large unit for the living room’.no see. In particular, the bedroom, where we spend the most time during the day, ranks first.

Capacity Calculation — Matching CADR to Room Volume

Air purifier performanceCADR (Clean Air Delivery Rate, amount of purified air per hour)Compare with . The basic formula is to select a capacity that can be ventilated 4 to 5 times per hour based on the room volume (area × ceiling height). For example, a bedroom with an area of 15㎡ and a ceiling height of 2.7m has a volume of about 40㎥, so a model with a CADR of 160~200㎥/h or more is appropriate. In heavily polluted places like Delhi, it is safer to choose one level more than the indicated capacity.

Pre-purchase checklist

True HEPA (H13 class or higher) filterMounted or not — Filter out the words ‘HEPA type’ and ‘HEPA-like’
CADR figuresIs it sufficient for the size of the bag?
Local availability of replacement filters— Brands with stable distribution are given priority as they are often sold out during the season.
night mode noise— Low noise mode is required for bedroom use
Real-time PM2.5 value display function — useful for judging ventilation timing

In India, Philips, Xiaomi, Honeywell, Sharp, Dyson, and Blue Air are widely distributed, and even among Korean brands, you can find products that have made inroads into India. The price is approximately 10,000 rupees for the entry-level model, and 30,000 to 50,000 rupees for the premium model (as of 2026, subject to change depending on model and time period), and online purchases such as Amazon and Flipkart are common. Online purchasing tipsGuide to using Amazon and FlipkartPlease refer to .

Lastly, filter management. Even if the manufacturer’s recommended replacement cycle is 6 to 12 months,The reality is that after one winter in Delhi, the filter life is reduced by less than half.no see. If the filter color has changed to dark gray, consider replacing it regardless of the value, and be sure to secure a spare filter before the start of the season (September to early October). In November, prices rise and items are sold out one after another.

Recommended air purifier in India — HEPA filter home air purifier installation view — It is a rule in Delhi winter to have an air purifier with an appropriate CADR capacity in each room rather than one for the living room. · Home Air Quality Guides (CC BY-SA 2.0, Wikimedia Commons)

05Masks and going out rules — from choosing an N95 to adjusting your daily movements

Equipment for going out during smog seasonN95 (or KN95·FFP2) or higher grade health maskis the default. Cloth masks or regular surgical masks have limited effectiveness in blocking PM2.5. The KF94 mask used in Korea is also a good alternative, so it is recommended that you bring plenty of it when you take office or visit.

Things to notefake productno see. During peak demand seasons, fake N95s imitating famous brands are commonly distributed in markets and online. Purchase from authorized distributors such as pharmacy chains (Apollo Pharmacy, etc.) or brand official stores, and avoid products with poor packaging or certification markings or abnormally low prices. To be effective, the mask must fit tightly to the face, so children must use the children's size.

Daily movement rules during smog season

Dawn/early morning and late evening are the worst parts of the day.This is the time when pollutants are spread on the ground due to the inversion layer, so switch morning outdoor exercise, such as jogging, to indoors during the season.
Ventilation is short in the middle of the day when levels are relatively low.It is realistic to look at the AQI app and only open it for 10-15 minutes during the low point of the day.
Circulation mode when moving the vehicleAs a basic rule, replace the cabin (air conditioner) filter before the season. The inside of a car is an unexpected blind spot for pollution.
After returning home, wash your hands and face, and drink plenty of water to protect your throat and bronchial mucosa. If the room is dry, humidification can also help.

Sore throat, cough, and itchy eyes are common symptoms during the season.If symptoms persist for a long time or a child or elderly person has difficulty breathing, do not wait and go to the hospital.How to use large private hospitals in Delhi NCRGuide to using hospitals in IndiaIt is organized in .

Check the authenticity of N95 mask — Beware of counterfeit products when choosing a mask to prepare for air pollution in Delhi — Fake N95 masks are common during the season. Buy from an authorized distributor, such as a pharmacy chain or official store. · w:User:SMS on the rocksj (CC0, Wikimedia Commons)

06Winter Smog Season Preparation Checklist — Get Started in September

Smog season in Delhi is an anticipated event. If you prepare in the order listed below starting in September when the monsoons are receding, you can get through the ‘worst week’ of November without too much trouble.

September — Equipment inspection/purchase:Check the operation of the air purifier, secure extra filters and N95 masks, and purchase a home PM2.5 meter if necessary. Price increases and sell-outs occur repeatedly just before and during the season.
Early October — Check your home for airtightness:Inspect window gaps and entrance door seals and install gaskets where necessary. Indian homes often have low airtightness of windows, so the impact of this work is greatly felt.
Before and after Diwali — Prepare for the worst part:The week or two immediately following Diwali are usually the worst of the year. It is best not to make any big plans such as outdoor events or moving during this time, and if annual leave is available, many families schedule trips to southern or coastal cities during this week.
In Season — Maintain a Routine:Make checking the AQI app a habit like checking the weather in the morning, and on days when the readings are good, make it a point to ventilate, spread the blanket, and do outdoor activities for your children. Drinking water frequently is also fundamental. Household drinking water managementGuide to Safe Drinking Water in IndiaPlease also refer to .
Check the school/company notice system:If GRAP is raised, school closures and online class conversion may be announced suddenly, so check the school announcement channel and the company's stay-at-home policy before the season.
Create a list of alternative indoor activities:If you list in advance indoor places you can go with your child, such as malls, kids cafes, and indoor sports facilities, the stress of 'no-go week' will be greatly reduced.

Lastly, I would like to give you some advice about your mindset. The smog season is not about ‘enduring winter’.‘Managing Winter’Please access . If you have the equipment and routine, you can keep the indoor air comfortable enough, and when the wind changes at the end of February, the air loosens like a lie. And with the monsoon from July to September, the season when Delhi's skies are the bluest returns.

Useful tips

Buy air purifiers and filters in September

When smog begins in earnest in November, prices for air purifiers and replacement filters rise and they are sold out one after another. Checking your gear in September, when the monsoon ends, and stocking up on spare filters and N95 masks in advance will give you plenty of room for the rest of the season.

Cross-check more than one AQI app

The Indian CPCB method and the US EPA method have different calculation formulas, so even for the same air, the numbers are different for each app. A realistic way to use it is to install at least two apps, such as the CPCB official SAMEER app and IQAir, and bookmark the observatory closest to your home.

Ventilation is brief during the low peak hours of the day.

In winter, early morning and late evening readings are the worst due to the inversion layer. An effective routine is to check the low point of the day (usually midday) on the AQI app, ventilate for only 10 to 15 minutes, and then turn the air purifier to maximum mode after ventilating.

Set the filter replacement cycle to half of what is indicated.

Even if the manufacturer recommends 6 to 12 months, the filter will turn dark gray after one Delhi winter. It is safe to check the condition of the filter in February or March, when the season ends, and replace it before the next season as the default.

Don't forget your car's cabin filter and air circulation mode.

The inside of a car is an unexpected blind spot of pollution. Replace the air conditioner cabin filter before the season, and set air circulation mode as the default when traveling. If you're hiring a driver, it's a good idea to check these two things yourself.

Common pitfalls and how to solve them

There are differences between the figures seen on IQAir and the Indian government app, making it confusing as to which is correct.

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Both are correct. The Indian CPCB and US EPA AQI calculation formulas are different, so even for the same air, different numbers are displayed. Rather than looking at the numbers themselves, look at the ‘rating (Poor, Very Poor, etc.)’ based on the app and decide what to do.

Thinking that the cloudy sky on a winter morning is fog, you go out without a mask.

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From December to January in Delhi, fog and smog mix together, making it difficult to distinguish with the naked eye. Make your judgment based on the AQI number, not the sky conditions, and wear an N95 mask if it is Poor (201) or higher.

Trying to cover the entire house with one large air purifier for the living room does not manage the air quality in the bedroom.

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Air purifiers operate in closed-door units. Place a CADR capacity of 4 to 5 times per hour in each room based on the room volume (area × ceiling height), but prioritize the bedroom where you stay the longest.

The N95 mask I bought in a hurry during the season is counterfeit and has no blocking effect.

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Fake N95s are common in markets and online in November when demand surges. Buy from pharmacy chains or official brand stores, and avoid products with poor packaging or unusually low prices. It is also a good idea to bring plenty of KF94 from Korea.

Due to the GRAP increase, schools suddenly switch to online classes, paralyzing the schedules of dual-income families.

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If the AQI enters the Severe zone, school attendance adjustments may be announced suddenly. Check the school's emergency announcement channel before the season, and agree in advance on any work-from-home or child care alternatives with your family.

Latest updates

Delhi NCR regularizes enforcement of GRAP step-by-step regulations every winterThe GRAP system, in which the NCR Air Quality Management Committee (CAQM) gradually initiates construction suspension, vehicle and diesel generator restrictions, and school class adjustments depending on the AQI level, is repeatedly implemented every winter. Detailed measures are adjusted every year, so it is necessary to check official notices during the season.
School closures and online classes are a recurring trend during the smog season.In November and December, when the AQI enters the Severe range, Delhi NCR schools have repeatedly stopped attending classes or switched to online classes in recent years. It is a good idea for families with children to check school emergency notification channels and child care alternatives before the season.

FAQ

When is Delhi air pollution most severe?

Smog season runs from the end of October to February of the following year, and November is usually the worst month of the year when stubble burning, Diwali fireworks, and stagnant air overlap. Conversely, the monsoon period from July to September is the cleanest time of the year.

Are India's AQI numbers the same as Korea's?

no. India uses the 6-level scale (Good to Severe) of 0 to 500 set by the CPCB, and the calculation formula is different from the US EPA, so even for the same air, the numbers are different for each app. It should be taken into account that Air Korea's 'very poor' standard (PM2.5 76 µg/m³ or higher) is routinely exceeded in Delhi during the winter.

What criteria should I use when choosing an air purifier?

A true HEPA (H13 or higher) filter and sufficient CADR (room volume × 4-5 ventilation per hour) relative to the room volume are key. It is more effective to place one in each room, giving priority to the bedroom rather than one large one for the living room, and it is important to choose a brand that has a stable supply of replacement filters.

What's it like at my child's school in the winter?

When the AQI enters the Severe zone and the upper level of GRAP is activated, adjustments to lower-grade classes or conversion to online classes may be announced, which has been repeated every winter in recent years. Check your school's emergency announcement channels in advance of the season and prepare alternative care options.

What kind of mask should I wear?

N95, KN95, FFP2 or higher grade health masks are basic, and Korean KF94 is also a good alternative. Since counterfeit products are common during the season, purchase them from authorized distributors such as drugstore chains or official stores, and children must wear children's sizes and wear them closely.

References & links

Central Pollution Control Board (CPCB) of India IQAir — World real-time air quality World Air Quality Index Project (aqicn.org)Air Korea — Korea air quality information World Health Organization (WHO)