Air Quality Index Cleanrooms

Air Quality Index (AQI) is a number and scale that measures how polluted or clean the air is. Using the air quality index, it’s possible to forecast how clean, safe or healthy an environment actually is.

The purpose of AQI is to help individuals living in a community or workers in a facility know how clean the air around their environment is, as well as highlight any dangers they could be exposed to. AQI varies from country to country; each location has its unique scale for grading or ranking the degree of pollution in a given area. The frequently used index in the UK – as given by the Committee on Medical Effects of Air Pollutants (COMEAP) – is known as Daily Air Quality Index (DAQI). It has 10 points divided into four groups or bands, with each band having its own unique characteristics and health risks.

With DAQI, you can measure how polluted your environment is; how risky it is to the health of people working or living in the area; and learn of recommendations or steps to take to be safe. The index is based on and calculated using the concentration of pollutants: Nitrogen Dioxide, Ozone, Sulphur Dioxide, Particles with an Aerodynamic Diameter less than 2.5μm, and Particles with an Aerodynamic Diameter less than 10μm.

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Air Quality Bands

DAQI has 10 values stretched over four bands. These bands have significant levels of pollution assigned to them, as well as measures to take for each band. The four bands are highlighted below, along with recommendations by the Department of Environment Food and Rural Affairs (DEFRA) on each:

1st Band (Low): DAQI has values from 1 – 3, whereby the environment is considered at its safest and normal activities can be carried out. Air pollution poses very little or no risk.

2nd Band (Moderate): DAQI has values from 4 – 6. This is considered normal, and the environment has safe levels of pollution. People who are sensitive to ozone might experience difficulty in breathing and unusual coughing. DEFRA recommends people with heart conditions should reduce strenuous activities.

3rd Band (High): DAQI has values from 7 – 9 and is the first unsafe level of pollution.  People with lung and heart conditions are at risk, while elderly people could experience difficulty in breathing. It’s not uncommon to experience sore eyes or throat and unusual coughing. DEFRA recommends people with these symptoms stay indoors and avoid strenuous activities. Asthmatic individuals might need to use inhalers more than usual.

4th Band (Very High): DAQI has a value of 10 and is considered very unsafe at all levels. Everyone is potentially at risk and may experience uncomfortable health symptoms. DEFRA recommends everyone with health conditions and such symptoms as cough, sore eyes or sore throat should stay indoors and re-schedule any strenuous activities.

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Calculation of Air Quality Index

Air Quality Index is calculated based on four major pollutants, as listed earlier: Nitrogen Dioxide, Ozone, Sulphur Dioxide, and Particulate Matter. A sub-index is calculated for each of these pollutants using the quantity (in μg) available per volume of air. The four sub-indices are then used to calculate the AQI for a particular location.


Ozone is found naturally in the air. However, some people are sensitive to ozone – especially ozone formed close to the earth’s surface when pollutants react chemically in the air.  0-100 µg/m³ (sub-index of 1-3) of Ozone in the air is considered safe, while quantities above 240µg/m³ (sub-index of 10) are considered very unsafe.

Nitrogen Dioxide

Nitrogen Dioxide is an oxide of Nitrogen. At high temperatures, it has a biting smell and is a dangerous pollutant. 0-67 µg/m³ of Nitrogen Dioxide in the air is considered safe, while quantities above 600µg/m³ are deemed very unsafe.

Sulphur Dioxide

Sulphur Dioxide is found mainly around various industries. It is very reactive, colourless and exudes a burnt match smell. 0-88 µg/m³ in the air is considered safe, while quantities above 1065µg/m³ are deemed unsafe.

Particulate Matter

This consists of mixtures of solid and liquid droplets. Particulate pollution affects people with lung conditions. Quantities between 0-88 µg/m³ of fine particles (less than 2.5μm in diameter) and 0-50 µg/m³ of coarse particles (from 2.5-10μm in diameter) in the atmosphere are considered safe, whereas quantities above 70µg/m³ for fine particles and 100µg/m³ for coarse particles in the air are very unsafe.

Formula for calculating AQI

I ( I_high- I_low )/(C_high- C_low ) (C- C_low )+ I_low

Where: I AQI
C Concentration of Pollutant (µg/m³)
C_low Minimum pollutant concentration of the band
C_high Maximum pollutant concentration of the band
I_low Sub-index of C_low,
I_high Sub-index of C_high.

Stay Safe with Total Clean Air

Although you can stay safe by avoiding strenuous work in your particular industry, Total Clean Air provides the opportunity to be efficient and productive, with safety guaranteed. We offer an extensive range of air monitoring and filtering products. With our modular cleanrooms, your workspace is secure and remains unaffected by the Air Quality Index of the surrounding environment. Our CTCB-I qualified Engineers will take a survey of your industry environment and recommend products for a healthier and safer workplace. So, contact Total Clean Air now.

Phillip Godden

Phillip Godden is the Founder & Chief/Executive Officer at Total Clean Air.

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