Don't run an engine in a garage or anywhere else without proper ventilation-EVER! Carbon monoxide is odorless and colorless. Your senses cannot detect its presence. Early symptoms of monoxide poisoning include headache, irritability, improper vision (blurred or hard to focus) and/or drowsiness. When you notice any of these symptoms in yourself or your helpers, stop working immediately and get to fresh, outside air. Ventilate the work area thoroughly before returning to the car. 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. 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 while 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 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 and hand cleaners available. Gasoline may contain additives which 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. If it is 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.
Due to special licensing (required in most states) and the high cost of recovery equipment, it is recommended that servicing (recovery, evacuation and charging) of the A/C system be left to a professional certified mechanic with the proper equipment and related training.