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.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 vehicle. Long hair should be kept under a hat or cap.Don't use pockets for toolboxes. A fall or bump can drive a screwdriver deep into your body. Even a wiping cloth hanging from a 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 grease-cutting soaps available. Gasoline contains chemicals that are harmful to body, it removes protective natural oils from the skin, leaves it dry, flaking and ready to absorb more oil and grease.Don't service the air conditioning system unless you are equipped with the necessary tools and training. If necessary to discharge the refrigerant system, a recovery/recycling station must be used. The refrigerant is extremely cold and when exposed to the air, will instantly freeze any surface it comes in contact with, including your eyes. Although the R-12 refrigerant (used on most models) is normally non-toxic, it 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 allow R-12 to enter a R-134a system, or vice versa. Never mix parts between systems as they are not compatible. This includes O-rings and refrigerant oil.Don't use screwdrivers for anything other than driving screws! A screwdriver used as a prying tool can snap when you least expect it, causing injuries. At the very least, you could ruin a good screwdriver.Don't use a bumper jack (that little ratchet, scissors, or pantograph jack supplied with the vehicle) for anything other than changing a flat! These jacks are only intended for emergency use on the road; they are NOT designed as a maintenance tool. If you are serious about maintaining your vehicle yourself, invest in a hydraulic floor jack of at least 1 1 / 2 ton capacity, and at least two sturdy jack stands. Do not use cinder blocks which can crumble and suddenly crush under the weight of the vehicle while you are working on it.