Don't run an engine in a garage or anywhere else without proper ventilation - ever! Carbon monoxide is poisonous; it takes a long time to leave the human body and you can build up a deadly supply of it in your system by simply breathing in a little every day. You may not realize you are slowly poisoning yourself. Always use power vents, windows, fans or open the garage doors.To avoid air bag deployment when the negative battery cable is disconnected, work must be started after approximately 20 seconds or longer from the time the ignition switch is turned to the Lock position and the negative battery terminal is disconnected from the battery.Don't work around moving parts while wearing a necktie or other loose clothing. Short sleeves are much safer than long, loose sleeves and hard-toed shoes with neoprene soles protect your toes and give a better grip on slippery surfaces. Jewelry such as watches, fancy belt buckles, beads or body adornment of any kind is not safe working around a car. Long hair should be hidden under a hat or cap.Don't use pockets for toolboxes. A fall or bump can drive a screwdriver deep into you body. Even a wiping cloth hanging from the back pocket can wrap around a spinning shaft or fan.Don't smoke when working around gasoline, cleaning solvent or other flammable material.Don't smoke when working around the battery. When the battery is being charged, it gives off explosive hydrogen gas.Don't use gasoline to wash your hands; there are excellent soaps available. Gasoline may contain lead, and lead can enter the body through a cut, accumulating in the body until you are very ill. Gasoline also removes all the natural oils from the skin so that bone-dry hands will suck up oil and grease.Don't service the air conditioning system unless you are equipped with the necessary tools and training. Refrigerants become extremely cold when exposed to the air and will instantly freeze any surface it comes in contact with, including your eyes. Although the refrigerant is normally non-toxic, R-12 becomes a deadly poisonous gas in the presence of an open flame. One good whiff of the vapors from burning refrigerant can be fatal.Don't lose track of your tools or parts. Wrenches left on fan shrouds and in the area of drive belts become potential missile hazards. Items like these usually find their way to an eye, face or limb or the engine. Scan the engine compartment for any loose tools or any parts that may have been replaced. It's great to be able to fix your car and save money and get satisfaction, but it's not worth the price of personal injury.