CLASSIFICATION OF PLACES WHERE EXPLOSIVE ATMOSPHERES MAY OCCUR

Preliminary note
The following system of classification must be applied to places where precautions in accordance with Articles 3, 4, 7 and 8 are taken.

1. Places where explosive atmospheres may occur

A place in which an explosive atmosphere may occur in such quantities as to require special precautions to protect the health and safey of the workers concerned is deemed to be hazardous within the meaning of this Directive.

A place in which an explosive atmosphere is not expected to occur in such quantities as to require special precautions is deemed to be non-hazardous within the meaning of this Directive.

Flammable and/or combustible substances are considered as materials which may form an explosive atmosphere unless an investigation of their properties has shown that in mixtures with air they are incapable of independently propagating an explosion.

2. Classification of hazardous places
Hazardous places are classified in terms of zones on the basis of the frequency and duration of the occurrence of an explosive atmosphere.
The extent of the measures to be taken in accordance with Annex II, Part A, is determined by this classification.

Zone 0
A place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is present continuously or for long periods or frequently.

Zone 1
A place in which an explosive atmosphere consisting of a mixture with air or flammable substances in the form of gas, vapour or mist is likely to occur in normal operation occasionally.

Zone 2
A place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

Zone 20
A place in which an explosive atmosphere in the form of a cloud of combustable dust in air is present continously, or for long periods or frequently.

Zone 21
A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionally.

Zone 22
A place in which an explosive atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

Notes:
1. Layers, deposits and heaps of combustible dust must be considered as any other source which can form an explosive atmosphere.
2. "Normal operation" means the situation when installations are used within their design parameters.

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Applications for gas monitoring

Chemical Industry
• Chemical Storage- toxic & flammable
• Manufacturing-toxic & flammable
• Laboratories-toxic, flammable & oxygen deficiency
• Emission Control-toxic

Oil & Gas
• Refineries-flammable
• Refineries-hydrogen sulphide
• Storage- as above
• Pipelines-as above
• Tank farms-flammable
• Drilling-flammable
• Drilling-hydrogen sulphide

Food Industry
• Food Processing-nitrogen (oxygen deficiency)
• Fruit Ripening-ethylene oxide
• Packaging-nitrogen
• Cold Storage-ammonia

Local Government
• Chlorination Plants-chlorine
• Pumping Stations-methane, oxygen
• Pumping Stations-hydrogen sulphide
• Sewage Treatment Plants-as above
• Landfill-methane, carbon dioxide
• Landfill-hydrogen sulphide

Transport
• Tunnels-carbon monoxide
• Car Parks-carbon monoxide
• Fuel Storage-flammable
• Battery Charging-hydrogen

Miscellaneous
• Hotel Kitchens-flammable
• Refrigeration-ammonia
• Greenhouses-carbon dioxide
• Breweries-carbon dioxide & oxygen
• Food Industry-ethylene oxide, nitrogen
• Paint Workshops-flammable
• Leather Tanning-hydrogen sulphide
• Effluent processing-methane
• Effluent processing-hydrogen sulphide
• Hospitals-oxygen, nitrogen
• School Laboratories-Flammable

see the sub-categories on the left