Division 1 cont'd

DOE-HDBK-1092-2004

1. Ignitable concentrations of flammable gases, liquids, or vapors can exist under normal

operating conditions;

Ignitable concentrations of such gases or vapors may exist frequently because of repair or

maintenance operations or because of leakage; or

Breakdown or faulty operation of equipment or processes might release ignitable

concentrations of flammable gases, liquids, or vapors and might also cause simultaneous

failure of electrical equipment.

Note: In each case, ignitable concentrations are mentioned. This means concentrations

between the lower and upper flammable or explosion limits (see Section 5.3.5 and Table 5-5).

The fine-print note to NEC 500.5(B)(1) describes a number of areas and occupancies normally

classified as Class I Division 1 locations.

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