INTRINSICALLY SAFE CLASSIFICATION
Classification of Areas (Division)
Areas are classified as Division 1or 2 as shown below. Since a Divi- sion 1 area is considered most hazardous, a transceiver approved for a specific Division 1 atmosphere can also be used in the same Division 2 atmosphere. The intrinsically safe rating applies to Division 1 areas and the nonincendive rating applies to Division 2 areas.
Division | Area |
1An area where there is or could be an explosive atmosphere most of the time in normal operations.
2An area where an explosive atmosphere exists only as a result of a fault (something going wrong).
Classification of Atmospheres (Class/ Group)
For the purposes of testing and approval, various atmospheric
mixtures have been grouped on the basis of their hazardous characteris- tics. Equipment is approved for a class of material and also for the specific group of gas, vapor, or dust in that class. Class I materials include gases and vapors, and Class II materials include combustible dusts. The typical hazardous materials in each group and class are shown in the following table.
ATMOSPHERE CLASSIFICATION
Typical Hazard | Group | Class |
Acetylene | A | 1 |
Hydrogen | B | 1 |
Ethylene, ethyl ether, cyclopropane | C | 1 |
Gasoline, naphtha, butane, propane, alcohol | D | 1 |
acetone, benzol, natural gas |
|
|
Metal dust including aluminum, magnesium, | E | 2 |
and their alloys |
|
|
Carbon black, coal or coke dust | F | 2 |
Flour, starch, or grain dusts | G | 2 |
Ignitable fibers/flyings such as rayon and cotton | – | 3 |
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