In one line
The Air Quality Index (AQI) is a number that shows how clean or polluted the air is around us.
A digital AQI display board, showing real-time air quality in a city.
Image: Wikipedia
The rule
The Air Quality Index (AQI) is a scale used to report the level of air pollution in a specific area, based on the amount of certain harmful substances in the air.
There is no single formula, but AQI is calculated using measured values of main air pollutants like PM₂.₅, PM₁₀, NO₂, SO₂, CO, and O₃.
Let's understand it simply
Imagine you are checking the weather before playing cricket. Just like you want to know if it will rain, you also want to know if the air is safe to breathe. The AQI is like a traffic signal for air. Green means the air is good, yellow means okay, and red means stop—air is bad for health. The higher the AQI number, the more polluted the air is.
How it works
- Special machines are placed in different parts of a city to collect air samples.
- These machines measure the amount of harmful substances (pollutants) in the air, like dust (PM₂.₅ and PM₁₀), gases (NO₂, SO₂, CO, O₃).
- Each pollutant's amount is compared to safe limits set by health experts.
- The worst (highest) value among these pollutants is chosen to decide the AQI for that place.
- The AQI number is given a colour and a health message (like good, moderate, unhealthy).
- Air samples are collected by machines.
- Pollutants like PM₂.₅, PM₁₀, NO₂, SO₂, CO, O₃ are measured.
- Each pollutant's value is compared to health limits.
- The highest value decides the AQI.
- AQI is shown as a number and colour.
The story behind it
The AQI was created because people needed a simple way to understand air pollution. Scientists and health agencies in many countries, including India, wanted to warn people when the air was unsafe. India started using its own National AQI system in 2014, making it easier for everyone to check air quality, just like checking the weather.
Where you see it in real life
- On news channels or weather apps: You see AQI numbers and colours for your city.
- At traffic signals in big cities: Electronic boards show AQI to warn people.
- During Diwali: AQI goes up because of firecrackers, making the air smoky.
- Near factories: AQI is often higher because of smoke and gases.
- In schools: Sometimes outdoor sports are cancelled if AQI is too high.
- On government websites: Daily AQI updates help people plan their day.
Why it matters
- Helps you decide if it's safe to go outside, especially for children and elders.
- Alerts people with asthma or breathing problems to take care.
- Guides the government to control traffic or close factories when air is very bad.
- Used in exams and projects to study pollution and health.
Common mistakes
- Thinking AQI is the same everywhere in a city—AQI can change from one area to another.
- Believing only dust causes high AQI—gases like NO₂ and O₃ also matter.
- Ignoring AQI numbers—high AQI can harm health even if you don't see smoke.
Remember it
AQI is like a report card for the air—higher marks mean more pollution, lower marks mean cleaner air.
Check yourself
What does a high AQI number mean?
It means the air is more polluted and can be harmful to health.
Name two pollutants measured for AQI.
PM₂.₅ (fine dust) and NO₂ (nitrogen dioxide).
Why is AQI important for children and old people?
They are more sensitive to air pollution and can get sick easily.
Why is AQI sometimes higher during Diwali?
Because firecrackers release a lot of smoke and harmful gases into the air.
Quick recap
- AQI tells you how clean or polluted the air is.
- It is based on measuring harmful substances in the air.
- A higher AQI means more pollution and more health risk.
- AQI is shown as a number and colour code.
- It helps people and authorities take action to protect health.