Emissions to the atmosphere of gaseous substances whose concentration exceeds the average content of these substances in the clean air, adversely affecting human health and the condition and quality of the environment.

Characteristic pollutants of the atmosphere in gaseous state refer to sulphur dioxide (SO2), nitric oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (CnHm) and so called "oxidizers". Oxidizers are secondary pollutants, produced in photochemical reaction of basic pollutants. They include ozone, nitrogen dioxide, formaldehyde, acrolein and others.

• Emission of air pollutants
• Exhaust gases
• Ambient concentration
• Neutralisation of gas pollutants