9ENG8008 GFM436 User Manual
Appendix B – Understanding Instruments For Use In Flammable Atmospheres- 78
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17 Appendix B – Understanding Instruments For Use In
Flammable Atmospheres
17.1 Hazardous areas classified by zones
There are three zones defined to guide users as to the necessary precautions which should be taken when working
in potentially flammable atmospheres:
Zone 0 - An area in which an explosive gas/air mixture is continuously present, or present for long periods.
Zone 1 - An area in which an explosive gas/air mixture is likely to occur in normal operation.
Zone 2 - An area in which an explosive gas/air mixture is not likely to occur in normal operation and if it does
occur will exist only for a short time.
Make certain that the area in which you intend to work can be described by one of the zones above.
17.2 Different types of gas
Different gases are grouped according to how easily they are ignited. Some examples are given below. (For other
gases please contact the manufacturer).
Gas Relative Ignition Group
Hydrogen/Acetylene Most easily ignited IIC
Ethylene IIB
Carbon monoxide IIB
Hydrogen sulphide IIB
Ammonia IIA
Propane IIA
Petrol vapour IIA
NOTE: This instrument is suitable for use in Zone 1 and 2.
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