What Is AQI and How Is It Measured? What Is a Good AQI Level?

The Air Quality Index (AQI) simplifies complex pollution data into a single number, providing a clear idea of how safe the air is for you to breathe. When you check your phone in the morning, understanding delhi aqi explained helps you make sense of those fluctuating figures and their impact on your health and daily life. This system takes raw measurements of common pollutants like particulate matter (PM2.5 and PM10), nitrogen dioxide, and ozone and compresses them into an easy-to-understand scale. Knowing what is aqi and how is it measured allows you to determine whether it's a good day for outdoor exercise or if it’s better to stay indoors.

What Is AQI and How Is It Measured?

AQI converts complex air-quality data into one number and a colour-coded category. India uses the CPCB National Air Quality Index. It covers 8 pollutants naming PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃ and Pb.

Pollutant	Definition
PM10	Inhalable particles or droplets with an aerodynamic diameter of 10 micrometres or less; they can enter the lungs. Sources include road and construction dust, soil dust, smoke and industrial emissions.
PM2.5	Microscopic combustion particles with diameters 2.5 micrometers or smaller (from vehicle exhaust and crop burning) that can penetrate deep into the lungs and enter the bloodstream.
NO₂	A reddish-brown, highly reactive gas in the nitrogen-oxides (NOₓ) family, mainly from vehicle exhaust and fossil-fuel combustion. It irritates airways and contributes to ozone and secondary particulate formation.
SO₂	A colourless gas with a sharp, irritating odour, released chiefly when coal, oil or other sulphur-containing fuels are burned in power plants and industry. It can cause breathing problems and contributes to acid rain and sulfate particles.
CO	A colourless, odourless, toxic gas formed by incomplete combustion of carbon-based fuels especially vehicle exhaust, stoves, fireplaces and generators. It binds to haemoglobin and reduces oxygen delivery to body tissues.
O₃	At ground level, a secondary pollutant and major component of smog; it forms when sunlight drives reactions among nitrogen oxides and volatile organic compounds. It is harmful to breathe, particularly for people with asthma or lung disease.
NH₃	A colourless gas with a pungent smell, mainly associated with agricultural activities, livestock waste, fertilizers and some industrial processes. In air, it can react with acidic pollutants to form fine particulate matter.
Pb	A toxic heavy metal that can be present as airborne particles from sources such as lead smelters, battery manufacturing, ore processing, contaminated dust, and aviation fuel containing lead. Exposure can harm the nervous system, kidneys and cardiovascular system.

These are measured by continuous ambient air quality monitoring stations run by CPCB, DPCC and state boards. In broader terms, these pollutants contribute in smog/pollutions people witness during winters here in India. GRAP stages are managed and enforced by Commission for Air Quality Management (CAQM).

How Is AQI Calculated?

Each pollutant gets a sub-index from its concentration using linear interpolation across breakpoints. The final AQI is the highest sub-index, so the worst pollutant sets the number. Mostly, 24-hour averages are used; 8-hour averages apply for CO and O₃. For validity, data for at least 3 pollutants, including PM2.5 or PM10, must be available with sufficient hours of data.

For instance, if PM2.5 levels are at 150 µg/m³, this might yield a sub-index of 200. If no other pollutant has a higher sub-index, the AQI reported will be 200.

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How Much AQI Is Good? (AQI Categories)

AQI	Category
0-50	Good
51-100	Satisfactory
101-200	Moderate
201-300	Poor
301-400	Very Poor
401-500	Severe

So, 0-50 is good; 51-100 is acceptable for most people. Health impacts vary by category, with extra advice for sensitive groups (children, elderly, asthma, and heart patients).

Why Is Delhi’s Air So Bad?

Winter drivers include low wind speed, temperature inversion and vehicular and construction dust. Seasonal peaks occur due to stubble burning (Oct-Nov), Diwali firecrackers, and cold, still mornings. GRAP stages are triggered based on pollution levels; verify current thresholds on the CAQM website.

The most polluted spot changes daily; usual hotspots include Anand Vihar, Wazirpur, Bawana, Mundka, and Jahangirpuri.

Delhi AQI This Week: Weekly AQI Tracker (Updated Every Monday)

Last updated: [October 27, 2026] | Data period: October 19, 2026 to October 27, 2026 | Source: CPCB/DPCC

Weekly Snapshot

Average AQI for the week: 297 (Severe)
Best day: October 24, 2026, 176 - 185
Worst day: October 26, 2026, 350 (Very Poor)

Highest AQI in Delhi This Week

Station: Pusa
Date: October 24, 2026
Value: 324 (Very Poor category)

Daily Delhi AQI Table (Mon-Sun)

Date	Delhi Average AQI (Overall)	Category	Highest Station Recorded
Mon, Oct 19	161	Moderate	Anand Vihar
Tue, Oct 20	179	Moderate	Mundka
Wed, Oct 21	227	Poor	Wazirpur
Thu, Oct 22	242	Poor	Anand Vihar
Fri, Oct 23	230	Poor	Pusa (324)
Sat, Oct 24	185 / 191	Moderate	Jahangirpuri
Sun, Oct 25	153 / 167	Moderate	Jahangirpuri (246)
Mon, Oct 26	248	Poor	Jahangirpuri
Tue, Oct 27	166/246	Severe	Chandni Chowk

Weekly AQI by Locality

Locality	Weekly Average
Dwarka	204
Delhi Cantt	185
Chhatarpur	168
Palam	181
Connaught Place	170
Laxmi Nagar	179
Patparganj	176
Greater Noida	158

Why Did AQI Rise or Fall This Week?

The fluctuation in Delhi's AQI during the week of October 19-25, 2026, was primarily driven by a combination of festive celebrations, shifting weather conditions and seasonal agricultural emissions.

How to Protect Yourself When AQI Is High

Check AQI before outdoor activity; use N95/FFP2 masks.
Keep windows closed at peak hours; use HEPA air purifiers.
Avoid outdoor exercise when AQI is Poor or worse.
Extra caution for children, the elderly and people with respiratory or heart conditions.

Summing Up

Staying informed about air quality is essential, especially in densely populated regions like Delhi. The delhi aqi explained highlights how air pollution levels can differ from one area to another, directly affecting our daily lives and health. By grasping what AQI numbers signify, you can take necessary precautions, particularly for vulnerable groups such as children, the elderly and those with pre-existing health conditions.

Keeping an eye on local AQI variations like aqi delhi dwarka or greater noida aqi enables you to make informed choices about outdoor activities. Elevated pollutant levels can lead to immediate health issues including respiratory problems and can have long-term effects such as lung damage. So, when you check the highest aqi in delhi today or the delhi aqi now, remember that these numbers represent the air you breathe and its potential impact on your health.

By tracking air quality updates and understanding the factors that influence these readings, you can better shield yourself and your family. Taking preventive measures on high AQI days, such as wearing masks or staying indoors, can greatly reduce your exposure to harmful pollutants. As we navigate the challenges of air pollution, remaining informed and proactive is crucial for protecting our well-being. Understanding the intricacies of the delhi aqi explained empowers you to take charge of your health amidst environmental challenges.

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Frequently Asked Questions

Find answers to common questions about this topic

What is a good AQI in Delhi? (0-50)

A "Good" AQI falls within the 0-50 range. In Delhi, this cleanest level is typically only achieved during the peak monsoon season (July to September) due to heavy rain washing away airborne particles.

How is AQI calculated in India?

CPCB calculates the AQI by measuring eight key pollutants (PM2.5, PM10, NO2, SO2, CO, O3, NH3, and Pb). Sub-indices are calculated for each pollutant based on 24-hour rolling averages and the highest individual sub-index value becomes the overall daily AQI.

What is the highest AQI in Delhi today?

According to live data monitored by the CPCB, the highest station AQI recorded today (October 26, 2026) in the national capital is 246 at Jahangirpuri.

Which pollutant matters most?

Fine particulate matter (PM2.5) is the most critical pollutant because its microscopic size allows it to bypass nasal filters and embed deep into the lungs and bloodstream. It remains the dominant contributor to Delhi's severe smog, especially during the winter stubble-burning season.

Why is AQI different in Dwarka and Patparganj?

Dwarka is highly impacted by open dust storms, unpaved roads and major traffic corridors near the city's edge, whereas Patparganj's pollution profile is heavily influenced by localized industrial zones and commercial freight traffic.

Is Ghaziabad or Greater Noida more polluted than Delhi?

Ghaziabad is slightly less polluted with an AQI of 177 while Greater Noida sits lower at 152–170, making Delhi the most polluted of the three today.

How often is the weekly AQI tracker updated?

The automated historical trend tracker compiles daily data logs and updates its consolidated weekly breakdown every Monday.

What Is AQI and How Is It Measured? What Is a Good AQI Level?

What Is AQI and How Is It Measured?