Understanding the Air Quality Index (AQI)

An air quality index indicates the average level of pollution in the air over a period of time. AQI systems vary by country and may represent differing types of pollutants. RIS and RIS Swiss Section use the US AQI standard, reported in real-time readings.

You can find Bangkok area air quality information from Airvisual here:


Air Quality and AQI

Especially during the winter months, the air quality in Bangkok can decrease significantly. Since the health of our students is a top priority at RIS Swiss Section, the school closely monitors daily particulate matter (PM 2.5) and AQI levels throughout the year. 

AQI measures are coordinated with RIS and aligned campus-wide. 

Which device do we use to measure air quality?

We use the readings from the AQI meter on the RIS campus as a guide. You can access this AQI sensor through the “AirVisual” app or the website using the following code: PF9071DI.

Instructions on how to set up the “AirVisual” app and add the RIS AQI monitor device for the most accurate local readings can be found here.

How does RIS Swiss Section keep indoor AQI levels low?

All classrooms and school offices have central air conditioning systems equipped with HEPA filters and additional high performance Xiaomi air purifiers.  This ensures consistent PM2.5 levels below the World Health Organization’s recommended 24-hour average of 25.

Is it dangerous to be outside if the AQI is high?

Air pollution is a growing concern worldwide, and research indicates that exposure to air pollution can impact our health. Although all air pollution is unhealthy regardless of the concentration, short-term exposure at moderate levels typically does not have a lasting impact. For this reason, most government sources and guidebooks do not specify that people should stay indoors at those levels, but rather that they should avoid prolonged

exertion. This is defined as outdoor activity that lasts several hours and causes breathing heavier than normal.

At AQI levels above 150 and below 200, most authorities simply recommend that sensitive groups, including children and older adults, avoid prolonged exertion for periods of several hours. However, evidence also indicates that short-term exposure to unhealthy air can create health concerns. Children are at an increased risk because their lungs are still growing, they tend to be more physically active, and they are more likely to have respiratory illnesses that can be aggravated when pollution levels are high.

Questions and answers

What is particulate matter?

Particulate Matter (PM) is the term used to describe particles in the air that do not immediately sink to the ground, but remain in the atmosphere for a certain amount of time. The tiny particles are not visible to the naked eye and can only be seen during certain weather conditions in the form of a haze. Depending on the diameter of the dust particles, fine dust is divided into so-called fractions:


PM 10: coarse particles with a diameter of less than 10 micrometers (μm).
PM 2.5: fine airborne dust with a diameter of less than 2.5 μm
PM 0.1: ultrafine particles with a diameter of less than 0.1 μm 

What are the sources of particulate matter?

Particulate matter can be of natural origin or generated by human activity.


Primary particulate matter originates from a direct source such as a combustion process, engine exhaust, tire wear, and certain industrial processes.


Secondary particulate matter, on the other hand, is first created by chemical reactions from gaseous substances such as sulfur and nitrogen oxides. Natural sources include emissions from volcanoes and oceans, as well as certain biogenic aerosols. Emissions of gaseous precursors from animal agriculture also contribute to secondary dust pollution.

Where do high and low levels of particulate matter occur?


High levels of particulate matter occur, for example, in places characterized by high traffic volumes or industrial infrastructures. Low levels often occur in rural areas far from emission sources. On a large scale, elevated levels of particulate matter are measured when meteorological conditions such as low wind speed and winter weather prevail, in which the upper air layers are warmer than the lower ones.

Is particulate matter also present indoors?


Polluted outdoor air also enters indoor spaces through open or leaky windows. Indoor emission sources – smoking, candles, cooking, open fireplaces et cetera – can significantly increase the dust concentration. Because of the different origins of fine dust particles in outdoor air and indoors, fine dusts are not directly comparable in their effects.

Why is fine dust harmful to humans?


The smaller dust particles are, the greater the risk that they will penetrate deep into respiratory tracts. Thus, they can reach areas from where they are not excreted when exhaled. In addition, hazardous substances such as heavy metals or carcinogenic polycyclic aromatic hydrocarbons (PAHs) can accumulate on the surface of dusts.

What can be done to reduce fine dust pollution?


Even as an individual, something can be done to reduce particulate matter pollution: By using public transportation and reducing vehicle trips, emissions of particulate matter will be reduced. Many things that help to save energy also serve to reduce air pollution. The most important means of doing this are increasing energy efficiency and using renewable energy sources:


using renewable energy sources to generate hot water and electricity

Saving energy through thermal insulation, low-emission building heating systems, and more conscious use of household appliances. 

What is the Air Quality Index?

The Air Quality Index (AQI) describes how polluted or clean the ambient air is. The AQI focuses on health effects that are felt within a few hours or days of breathing polluted air. The calculation reflects air pollution from six pollutants: sulfur dioxide (SO₂), nitrogen dioxide (NO2), carbon monoxide (CO), ground-level ozone (O3), particulate matter less than 10 micrometers in diameter (PM 10), and particulate matter less than 2.5 micrometers in diameter (PM 2.5).


An individual AQI is determined for each pollutant and the final AQI is equal to the highest value of the six individual AQI values. The AQI values in Europe, America and China are only comparable to a limited extent, as different formulas and standards are used in their calculation depending on the country.

Where can I find out more about air quality?

Further information is available in German from the Federal Environment Agency and in English from the World Health Organization.