Pulse jet engines get extremely hot once started, and use very volatile fuels like gasoline or methyl-ethyl-ketone (as contrasted to relatively benign, although flammable, glow engine fuel). Contact of any type with the tailpipe of the engine is certain to result in severe burns, as the engine reaches red-hot temperatures in seconds. The airplane itself needs some sort of insulation to prevent catching fire on the ground before forward motion provides cooling air, and fully enclosed engines can set the airplane on fire after landing. The airplane should be launched as soon as possible after the engine starts to prevent heat buildup. The spark unit used for starting can also deliver a substantial electrical shock. A fire extinguisher should be at hand at all times when operating the engine. The engine is exceptionally loud when operating and should be operated with hearing protection to prevent damage.