What is AQI (Air Quality Index)?

by Karl von Luckwald / December 25, 2022

What is AQI? The Air Quality Index (AQI) is a measure of the air quality in a given area, and it helps individuals understand the air they are breathing. The AQI is calculated based on five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter PM2.5 or PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide.

A “traffic light” system for air quality

When the levels of these pollutants are high, it can have serious health consequences for individuals, particularly for those who are more vulnerable such as children, the elderly, and those with preexisting respiratory or cardiovascular conditions.

The AQI is calculated on a scale from 0 to 500, with higher numbers indicating poorer air quality. An AQI of 100 or below is considered satisfactory, while an AQI above 100 is considered unhealthy, with specific categories for unhealthy, very unhealthy, and hazardous.

One way to understand the AQI is to think of it as a “traffic light” system, with green indicating good air quality, yellow indicating caution, and red indicating unhealthy or dangerous air quality.

What is AQI? A "traffic light" system that helps people to understand the air they are breathing
The Air Quality Index (AQI) can be seen as a traffic light system that helps individuals understand the quality of the air that they are breathing

What is AQI based on?

AQI is designed to be easy to understand and to provide a consistent way of reporting air quality information across different locations and different types of pollutants.

The AQI is based on the concentration of certain pollutants in the air, including particulate matter PM2.5 and it is calculated using a formula that takes into account the concentrations of these pollutants and converts them into a single number on a scale from 0 to 500.

AQI cubicmeter
The AQI value is based on the concentration of certain pollutants. 0 -12 microgram/cubic meter of fine dust PM2.5 refer to an AQI value between 0 and 50 and is considered not harmful to health.

The AQI is important because it helps people understand the potential health impacts of the air they breathe and take steps to protect their health when necessary. It is also used by government agencies and other organizations to issue alerts and warnings when the air quality is expected to be poor and to take steps to improve air quality and reduce the negative impacts on human health.

What AQI value is good?

Generally, it is best to aim for an AQI value of 0 to 50, which indicates good air quality. This means that the air is relatively free of pollutants and the potential health risks associated with exposure to these pollutants are low.

good air quality in an office
AQI value of 38 is considered good air quality

If the AQI is higher than 50, it is still considered acceptable for most people, but certain groups, such as children, older adults, and people with respiratory or other health conditions, may be more sensitive to the pollutants in the air and may experience more severe symptoms at these levels.

What AQI value is bad?

If the AQI is higher than 100, it is considered unhealthy for sensitive groups and it is recommended that these groups take precautions to protect their health. If the AQI is higher than 200, it is considered very unhealthy and it is recommended that everyone take steps to protect their health. If the AQI is higher than 300, it is considered hazardous and it is recommended that everyone take steps to protect themselves from the pollutants in the air.

Unhealthy air quality in an office
AQI 153: Air quality in this office is unhealthy and exposes people to health risk

What is the difference between US AQI and Chinese AQI?

Different countries have different standards and guidelines for what constitutes acceptable levels of air pollution, and they may use different methods for measuring and reporting air quality. For example, the US has stricter standards for particulate matter (PM) than China, and as a result, the AQI for PM may be lower in the country with stricter standards.

While according to American guidelines, a fine dust content of more than 35 micrograms per cubic meter is already considered unhealthy, the Chinese method starts to consider values at a minimum of 75 micrograms per cubic meter as potentially harmful. That’s quite a difference.


Karl von Luckwald

Karl von Luckwald

Since moving to Thailand in 2019, Karl noticed the lack of scientific integrity in air purifier and water filter reviews. In response, he founded WE DO AIR to champion unbiased, science-based evaluations and empower consumers to make better-informed decisions.

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