Issue 1 and Volume 118.

INDUSTRIAL FIRE SAFETY DEPARTMENTS THE RATING of fire extinguishers is a subject which, it would seem, needs some explanation. The classification numbers stamped on the Underwriters’ Laboratories approval label (Figure 1), applied to every approved fire extinguisher, has for many years caused confusion among firemen and industrial fire brigade members. This classification is intended to indicate the fire extinguishing ability, or effectiveness, of that particular extinguisher, when used by an inexperienced operator of average intelligence. These ratings are based upon the results of very exacting tests conducted under actual fire conditions by the UL. The classification number also is used as a basis for determining the minimum number of extinguishers (many industries provide additional extinguishers) required for the protection of any building, depending upon the inherent hazard of the occupancy of the particular building. Almost all buildings—regardless of how fire-resistant the structure may be—will have combustible contents. Consequently, it is…

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