E.F. Johnson Company 5100 ES, Service Manual

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1-12 5100 ES Series Portable Radio Service Manual January 2007
General Information
1.6.5.1 Classification of Hazardous Areas (Division)
Hazardous areas are classified as Division 1 or 2 as shown in Table 1.2. Since a Division 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.
1.6.5.2 Atmosphere Classification (Class/Group)
For the purposes of testing and approval, various atmospheric mixtures have been grouped
on the basis of their hazardous characteristics. 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, Class II materials include combustible dusts, and Class III
materials include ignitable fibers or flyings. The typical hazardous materials in each group
and class are shown in Table 1.3.
Table 1.2 Area Classification
Division Area
Class I and II Materials (Gases, Vapors, and Dusts)
1
An area where there is or could be an explosive
atmosphere most of the time in normal operation
2 An area where an explosive atmosphere exists only
as a result of a fault (something going wrong)
Class III Materials (Fibers or Flyings)
1
An area in which easily ignitable fibers or materials
producing combustible flyings are handled,
manufactured, or used.
2 An area in which easily ignitable fibers are stored or
handled. An exception is in process of
manufacture.
Table 1.3 Material Classification
Typical Hazard Group Class
Acetylene A I
Hydrogen B I
Ethylene, ethyl ether, cyclopropane C I
Gasoline, naphtha, butane, propane,
alcohol, acetone, benzol, natural gas
D I
Metal dust including aluminum,
magnesium, and their alloys
E II
Carbon black, coal, or coke dust F II
Flour, starch, or grain dusts G II
Ignitable fibers/flyings such as rayon or
cotton
- III