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354 Gas Turbine Handbook: Principles and Practices<br />

Appendix C-4<br />

Classification of<br />

Hazardous Atmospheres<br />

Area classification are divided into CLASS, DIVISION, and<br />

GROUPS. As shown in the following table:<br />

CLASS DIVISION GROUP<br />

I Gases, 1 Normally A Acetylene (581°F)<br />

Vapors Hazardous B Hydrogen (968°F)<br />

C Ethylene (842°F)<br />

D Fuels such as:<br />

Methane (999°F)<br />

Propane (842°F)<br />

Butane (550°F)<br />

Gasoline (536-880°F)<br />

Naphtha (550°F)<br />

I Gases, 2 Not Normally A Same as Div. 1<br />

Vapors Hazardous B Same as Div. 1<br />

C Same as Div. 1<br />

D Same as Div. 1<br />

II Combust- 1 Normally E Carbonaceous metal dust<br />

ible Dust Hazardous F Carbonaceous dust<br />

Resistivity >10 2 and 10 8 ohm-centimeter<br />

2 Not Normal- F Carbonaceous dust<br />

ly Hazardous<br />

Resistivity >10 5 ohm-centimeter<br />

Same as Div. 1<br />

III<br />

Easily<br />

Ignitable<br />

Fibers and<br />

Flyings<br />

The above information has been extracted from NFPA 70-1990, National Electric<br />

Code. National Electric Code and NEC are Registered Trademarks of the National<br />

Fire Protection Association, Inc. Quincy, MA.

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