What is the AQI index? Learn about the Air Quality Index

What is the AQI index, and why is it important for human health? In the context of rising air pollution, understanding the AQI index will help people take proactive steps to protect their health. Learn more with Tan Thanh.

1. Overview of the AQI index

What is AQI and its role in air pollution monitoring?

The Air Quality Index (AQI) is a tool developed to provide quantitative information about the level of air pollution in a specific area at a given time.

AQI helps convert the concentration of air pollutants (measured in µg/m³ or ppm) into an easily understandable scale, typically ranging from 0 to 500. The higher the index, the more severe the pollution. This allows regulators, businesses, and citizens to assess the danger levels and take timely measures to protect health or control emissions.

6 main pollutants in AQI 

According to international standards such as EPA (USA) or QCVN 05:2013/BTNMT (Vietnam), the AQI index is made up of 6 main air pollutants. Each of these pollutants directly impacts human health and ecosystems, including:

• PM2.5 (fine particulate matter): Dust particles with a diameter of 2.5 microns or less. These are the most concerning because they can penetrate deep into the alveoli, causing pneumonia, asthma, and various cardiovascular diseases.
• PM10 (coarse particulate matter): Dust particles with a diameter less than 10 microns. While they don’t penetrate the lungs as deeply as PM2.5, they still cause irritation in the nose, throat, and eyes.
• O₃ (ground-level ozone): Unlike beneficial ozone in the upper atmosphere, ground-level ozone is formed by the reaction of sunlight with industrial or traffic emissions, causing respiratory inflammation and reducing lung function.
• CO (carbon monoxide): A colorless, odorless gas that is highly toxic. CO prevents oxygen from binding to hemoglobin in the blood, causing suffocation and death if exposed to high concentrations.
• SO₂ (sulfur dioxide): Emitted from the combustion of fossil fuels containing sulfur. SO₂ irritates the respiratory system and is a precursor to acid rain.
• NO₂ (nitrogen dioxide): Primarily emitted from vehicle engines and industrial furnaces. NO₂ increases the risk of bronchitis, especially in children.

2. AQI scale and its impact on health

To easily understand the impact of air pollution levels, the AQI index is divided into categories from “Good” to “Hazardous.” Below is the AQI classification table:

If the AQI remains high for an extended period, the result is an increase in chronic diseases, as confirmed by many scientific studies, including reports from the WHO (World Health Organization).

Vulnerable groups include:

• Elderly: Decreased immunity and lung function with age, making them more susceptible to respiratory irritation and heart disease.
• Children: Incomplete lung development and immune systems, making them prone to inhaling fine dust, which causes asthma and pneumonia.
• People with underlying health conditions: Cardiovascular, hypertension, and chronic respiratory diseases may worsen in poor AQI conditions.
• Pregnant women: Studies show that high AQI levels are associated with premature births, low birth weights, and neurological development disorders.

Common chronic diseases caused by prolonged exposure to high AQI levels include:

• Chronic obstructive pulmonary disease (COPD)
• Hypertension, heart attacks, strokes due to atherosclerosis
• Lung cancer and other respiratory-related cancers
• Endocrine disorders, liver and kidney dysfunction from heavy metal absorption
• Long-term impacts on cognition, learning, and memory

3. Air pollution status in Vietnam

According to data from AirVisual, air quality in Hanoi and Ho Chi Minh City has fluctuated significantly over the past 5 years, as reflected in the average AQI index.

AQI in Hanoi

After the “calm period” due to social distancing measures in 2020–2021, the AQI index in Hanoi has significantly increased, especially from 2023 onwards. In 2025, the average AQI index reached 109, exceeding the average threshold and approaching a “poor” level.

The main reasons include:

• The burning of straw after harvest remains common in suburban areas, despite numerous public awareness campaigns and penalties. Emissions from this biomass burning process are rich in CO, PM2.5, and asphyxiating gases.
• Infrastructure construction activities, particularly the construction of Ring Road 4 and high-rise building projects, generate large amounts of dust that are not effectively controlled. The dust suppression measures, such as covering and watering construction sites, are often superficial.
• Inversion frequently occurs during the winter, causing fine dust to be compressed at lower levels, making it difficult to disperse.

AQI in Ho Chi Minh City

Although the AQI level is significantly lower than in Hanoi, since 2023, Ho Chi Minh City has been recording a rising trend, especially in the dry months.

The main reasons in Ho Chi Minh City include:

• The crowded urban traffic, particularly motorcycles and small trucks, remains the primary source of fine dust and NO₂.
• There is less straw burning and heavy industry, but the lack of a coordinated air monitoring system means that AQI alerts are slow and inconsistent.
• The tropical humid climate helps disperse pollutants faster during the rainy season, but the dry season creates conditions that allow fine dust to accumulate in the air.

4. Measures to improve and reduce AQI levels

To reduce AQI and improve air quality, close cooperation is needed between authorities, businesses, and the community. Some effective solutions include:

• Reducing emissions from transportation: Encourage people to use public transportation, electric vehicles, and reduce dependence on personal vehicles that use fossil fuels. Investing in public transportation infrastructure will significantly contribute to reducing emissions from personal vehicles.
• Controlling pollution from industry: Factories and industrial zones need to adopt advanced technologies for exhaust gas and industrial dust treatment before releasing emissions into the environment. Installing effective air and dust filtration systems not only helps reduce pollution but also enhances production efficiency.
• Applying effective dust filtration technology: Equipping modern dust filtration systems is a key solution in reducing air pollution in high-pollution areas. These technologies help prevent fine dust PM2.5 and other harmful pollutants from being released into the environment.
• Increasing green spaces and planting trees: Planting green trees and creating green spaces helps absorb CO2 and pollutants while providing a cleaner environment for the community. Trees also help regulate the climate and improve the natural air quality.
• Public awareness and education: Education and awareness campaigns need to be implemented to help people understand the importance of protecting the air and their health. Every individual should be equipped with knowledge on how to reduce pollution in daily life, from using green transportation to minimizing waste burning.

5. Tan Thanh – Provider of certified industrial dust filtration solutions

With the increasing air pollution, the demand for quality industrial dust filtration solutions is growing. Tan Thanh is a trusted provider of industrial dust filtration solutions, offering modern dust filters, air purifiers, and other equipment to remove fine dust, emissions, and pollutants from production environments.

Tan Thanh focuses on quality, ensuring that all products meet international standards for filtration effectiveness, durability, and safety. The company also offers maintenance and servicing to ensure the devices remain operational and efficient over the long term.

Why choose Tan Thanh?

• Extensive experience: Expert team providing tailored solutions for dust collection, air filtration, and emissions control.
• Modern technology: Using advanced systems to ensure high effectiveness.
• Comprehensive support: From surveys and design to installation and maintenance, Tan Thanh supports businesses throughout their operations.

Understanding what is the AQI index and taking measures to improve air quality will help us live in a safer, more sustainable environment. Tan Thanh’s effective industrial dust filtration solutions play a crucial role in reducing pollution, protecting the health of workers and the community.

Contact Us:

• Hotline: 0917 531 007
• Email: kelvin@tatafilter.com
• Address: 50 Road No.1 Cu Xa Dien Luc, Truong Tho Ward, Thu Duc City, Ho Chi Minh City, Vietnam.