Explosive atmosphere
A mixture of air and one or more flammable substances in the form of gases, vapours, mists or dusts which, after ignition, causes combustion to spread to the entire unburned mixture. Areas with explosive atmosphere risk must be classified into zones.
Also known as
By jurisdiction
UK HSE
“explosive atmosphere”Exact equivalent“Defined in DSEAR 2002 (regulation 2(1)) as a mixture of air and one or more dangerous substances in the form of gases, vapours, mists or dusts in which combustion spreads after ignition to the entire unburned mixture. Employers must classify places where explosive atmospheres may occur into zones (Zone 0, 1, 2 for gases; Zone 20, 21, 22 for dusts).”
Irish HSA
“explosive atmosphere”Close equivalentThe Safety, Health and Welfare at Work (Explosive Atmospheres) Regulations 2003 implement the ATEX Workplace Directive in Ireland. Explosive atmosphere is defined consistently with the EU Directive. Area classification into zones is required.
US OSHA
“hazardous location”Close equivalentOSHA addresses flammable and explosive atmospheres in 29 CFR 1910.307 using a division classification system (Class I, II, III; Division 1, 2) derived from the National Electrical Code. This differs from the ATEX zone system but serves the same purpose.
Practitioner note: Zone classification drives equipment selection. Installing non-rated equipment inside a classified zone is a common and serious finding.