What is Aqi? How it calculate? pm2.5 vs pm10 vs O3

AQI={(I_high-I_low)/(C_high-C_low)}​{C – C_low} + I_low

C → Measured concentration of that pollutant

C_low → Lower limit of the concentration range

C_high → Upper limit of the concentration range

I_low → Lower limit of the AQI index

I_high → Upper limit of the AQI index

In this, the index is calculated based on concentration.

The concentration range and AQI range are different for each pollutant.

Example Calculation (PM2.5)

Let’s say the value of PM2.5 = 85 µg/m³.

Breakpoint table for PM2.5 (US-EPA):

AQI Range PM2.5 µg/m³
51-100 12.1-35.4
101-150 35.5-55.4
151-200 55.5-150.4

85 falls in this range: 55.5-150.4 → AQI 151-200

So:

C = 85

C_low = 55.5

C_high = 150.4

I_low = 151

I_high = 200

Now the formula Apply:

So AQI ≈ 166 (Very Unhealthy for sensitive groups)

Important Note

AQI is always rounded to the nearest integer.

The Total AQI is not the AQI of a single pollutant, but the worst AQI among six pollutants.

This means the pollutant with the highest AQI is the Final AQI.

Now let’s see what the air condition is between 0 and 500.

First, let’s talk about the range between 0 and 500. Look, it can’t be zero.

An AQI number between zero and 50 means the air is clean. You can breathe that air without fear. You can roam anywhere. You can go anywhere freely. But as the number increases, the situation starts to become a little serious. If the number is 50 to 100, you can still consider the air clean. There may be some minor problems. There are some highly sensitive people who have problems with even a little dust in the air. So they should use masks and such. Normal people don’t face any problems inside. However, when the air quality index starts to rise above 100, problems begin. If the AQI is between 100 and 200, then people with asthma, heart problems, or lung problems start to experience problems. Even normal people may experience some discomfort, such as a sore throat or other minor problems. But if the AQI rises above 200, the situation becomes very serious. Between 200 and 300, we assume that the air quality has deteriorated significantly. So, if your AQI is above 200, you should use a mask when going out.

Now, when does the situation become extremely serious?
When the AQI rises above 300, understand that the air is absolutely unfit for breathing.

What we do in this situation?

In such a situation, you should only leave the house when absolutely necessary. Otherwise, stay at home. And whenever you go out, use an N95 mask
or a pollution mask.

So, as soon as our Air Quality Index reaches above 300, the situation begins to become serious. So what should you do? In such a situation, you can plant purifying plants at home. That means, there are plants in small pots that can purify the air.

And also, in such a situation, consume a little more water. That will also help you in dealing with such a situation.

Because of this, your lungs will remain slightly hydrated.