Copyright Goodheart-Willcox Co., Inc. 60 Section 1 Introduction to Automotive Technology Explosions An explosion is the rapid, almost instant, combustion of a material that causes a powerful shock wave. Sources of potential explosions in an auto repair facility include hydrogen gas, fuel and fuel tanks, special sodium- filled engine valves, welding tanks, and propane tanks. Keep heat sources, sparks, and flames away from these combustible materials. Do not overheat or puncture containers, as this may also cause an explosion. Hydrogen Highly explosive hydrogen gas can settle around the top of a 12-V car battery that is being charged or discharged (used). The slightest spark or flame can ignite the hydro- gen gas, which can cause the battery to explode. Battery acid and pieces of the battery case can blow into your eyes and face. A battery explosion may cause cuts, acid burns, scars, and blindness. Always wear eye and face protection when working around a car battery. See Figure 5‑8. Fuel Tanks Fuel tanks, even seemingly empty ones, can explode. A drained fuel tank may contain fuel gum and varnish. When this gum is heated, it can emit combustible vapors. Keep sparks and heat away from fuel tanks. When a fuel tank explodes, one side will usually blow out and cause the tank to fly in the opposite direction. You or other workers could be killed or seriously injured. Air Bags Air bags are inflatable bags that help protect a vehicle’s occupants during a collision. An air bag shoots out at about 200 mph (320 kph), and is fully inflated within a fraction of a second. When you are removing or installing an air bag that has not been deployed, you must handle it with extreme care. The controlled explosion that causes the bag to deploy and the resulting force can break bones or kill. Read the manufacturer’s instructions on removal and installation of air bags to prevent an accidental deployment. Asphyxiation Asphyxiation occurs when a person is deprived of oxygen. It can be caused by breathing toxic or poisonous substances. Mild cases of asphyxiation will cause dizziness, headaches, and vomiting. Severe asphyxiation can cause death. The most common cause of asphyxiation in an auto shop is the exhaust gas produced by running automobile engines. Exhaust gases are poison. Always ensure that the vehicle’s tailpipe is connected to the shop’s exhaust ventilation system when the vehicle is running in the shop. See Figure 5‑9. Respiratory Protection Other shop substances that are harmful if inhaled include brake lining dust, clutch disc dust, parts clean- ers, and paint spray. Respiratory protection should be worn when you are working around airborne impurities. Dust masks are made of treated paper and will prevent large particles from entering your lungs. A respirator is a face mask with one or two filters that can prevent you from breathing small particulates, such as the asbestos in brake and clutch assemblies. See Figure 5‑10. Chemical Burns Solvents (parts cleaners), battery acid, and various other corrosive shop substances can cause chemical burns on your skin. Always read the directions and understand the safety procedures when working with Warning Always carry an undeployed air bag with the trim cover pointed away from your body and away from other people. A B C Eldred Lim/Shutterstock.com Figure 5-8. Certain types of eyewear protection are available with prescription lenses. A—Some safety glasses have side shields to prevent objects from going behind the lens. B—Safety goggles offer more protection against splashing liquids than safety glasses offer. C—Face shields protect your eyes, as well as your face. tankist 276/Shutterstock.com Pavel Skopets/Shutterstock.com