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NOTE: This is an unformatted excerpt from our online fire protection training library.

Classification Basics

Electrical Equipment

Reducing the Ignition Hazard

Reducing the Ignition Hazard

The ignition hazard presented by electrical equipment that must be located in a classified area may be reduced in two basic ways:

Isolating the ignition source Isolating the ignition source:
Ignition sources are typically isolated from contact in ordinary locations through the use of enclosures. In classified areas the enclosures must also isolate the ignition sources from the atmosphere, so specially designed enclosures like the one shown here are often required. Ignition sources may be isolated in other ways, such as by removing them from the classified area.

Limiting the energy of the ignition source Limiting of the energy of the ignition source:
Different materials require differing amounts of energy for ignition. The minimum ignition energy levels are well defined for many gases and vapors and less well defined for dusts. Typically, the energy required to ignite dusts are many times higher than the energy required to ignite gases and vapors, but the precise levels depend on the specific materials involved. In any case, where energy sources can be designed to limit their energy to levels less than the minimum ignition energy, they will not provide an ignition source, and special enclosures and wiring methods are not needed.

A dust-ignition-proof panelboard for use in Class II areas.
NOTE: This is an unformatted excerpt from our online fire protection training library.

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