2026 OTH Boat Crew Practice Test – The Complete Study Guide to Master Your Exam!

When a fire involves ordinary combustibles like wood, paper, and cloth (Class Alpha), the smoke that rises is typically white or gray. This happens because the fuels in these materials burn with a lot of water vapor and light-colored particulates from cellulose, producing lighter, less sooty smoke. In contrast, fires fueled by oils, gasoline, or other hydrocarbons tend to produce dark, black smoke due to a higher amount of soot and unburned hydrocarbons. Blue or red smoke isn’t associated with these common household or structural combustibles. So white or gray smoke best indicates a Class Alpha fire.