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Classes and Labeling
By Elizabeth A. Ginns — April 2003
Class A fires are classified by any solid combustible material (i.e. wood, paper, fabric) that leaves an ash behind. The numerical rating on a Class A fire extinguisher represents the amount of water the extinguisher holds and the amount of fire it can extinguish.
Class B fires refer to any flammable liquids, such as grease, gasoline, diesel, paint thinners, teak oil, acetone, varnishes, etc. Class B fires typically produce a thick, black, oily smoke. The numerical rating represents the square footage of the burning surface that could reasonably be extinguished.
Class C fires are caused by energized electrical equipment. This class of fire extinguisher does not have a numerical rating. The C label on the extinguisher indicates that the extinguishing agent is nonconductive.
Class D fires are categorized by all flammable metals and other rare substances that require special extinguishing agents and/or techniques. Class D extinguishers do not have a pictoral label like the other classes of extinguishers do, nor are they given a multipurpose rating for use on other types of fires.
The new fire extinguishing labels have multiclass ratings. This particular label indicates that the extinguisher is suitable for both a Class A and Class B fire. The red line indicates what type of fire an entinguisher is not suitable for, which, in this case, would be a Class C fire.
This article originally appeared in the March 2003 issue of Power & Motoryacht magazine.