Copyright Goodheart-Willcox Co., Inc. 19 Chapter 2 ∣ Shop Safety and Environmental Protection The following three conditions must be present at the same place and time in order for combustion to occur: • Oxygen must be present. • There must be a supply of burnable material, or fuel, available. • The temperature must be above the fuel’s flash point. Four basic types of fires can occur in a typical motorcycle shop. Each fire type has its own characteristics and requires a different type of extinguishing medium. See Figure 2-8. Goodheart-Willcox Publisher Figure 2-8. Fire classifications and the fire extinguishers used for each type of fire. Fires Type Use Operation Class A Fires Ordinary Combustibles (Materials such as wood, paper, textiles.) Requires: cooling/quenching A Old New Soda-acid Okay for use on A Direct stream at base of flame. Bicarbonate of soda solution and sulfuric acid Not for use on B C D Pressurized Water Okay for use on A Direct stream at base of flame. Water under pressure Not for use on B C D Class B Fires Flammable Liquids (Liquids such as grease, gasoline, oils, and paints.) Requires: blanketing or smothering B Old New Carbon Dioxide (CO2) Okay for use on B C Direct discharge as close to fire as possible, first at edge of flames and gradually forward and upward. Carbon dioxide (CO2) gas under pressure Not for use on A D Class C Fires Electrical Equipment (Motors, switches, etc.) Requires: a nonconducting agent C Old New Foam Okay for use on A B Direct stream into the burning material or liquid. Allow foam to fall lightly on fire. Solution of aluminum sulfate and bicarbonate of soda Not for use on C D Dry Chemical Multipurpose type Ordinary BC type Direct stream at base of flames. Use rapid left-to-right motion toward flames. Class D Fires Combustible Metals (Flammable metals such as magnesium and lithium.) Requires: blanketing or smothering D Old New Okay for C A B Okay for C B Not okay for D Not okay for A D Dry Chemical Okay for use on D Smother flames by scooping granular material from bucket onto burning metal. Granular-type material Not for use on C A B