R-12 Systems

R-12 is a Freon refrigerant that is odorless and colorless both as a gas and as a liquid. Since it boils (vaporizes) at ±21.7°F, it will usually be in its vapor state while being handled during repairs. However, if a portion of the liquid coolant should come in contact with the hands or face, the momentary -22°F refrigerant temperature can cause serious injury. Use of an approved R-12 recovery device is required when it is necessary to discharge the A/C system for any reason.
Protective goggles should be worn when opening any refrigerant lines. If liquid coolant does touch the eyes, bathe eyes quickly in cold water, then apply a bland disinfectant oil. See an eye doctor.

When checking a system for leaks with a torch type leak detector, do not breathe vapors coming from the flame. Do not discharge the refrigerant in an area of a live flame. A poisonous phosgene gas is produced when R-12 is burned. While the small amount of gas produced by a leak detector is not harmful unless inhaled directly at the flame.

Never allow the temperature of refrigerant drums to exceed
125°F. The resultant increase in temperature will cause a corresponding increase in pressure, which may cause the safety plug to release or the drum to burst.
If it is necessary to heat a drum of refrigerant when charging a system, the drum should be placed in water that is no hotter than
125°F. Never use a blow torch or other open flame. If possible, a pressure release mechanism should be attached before the drum is heated.

When connecting and disconnecting service gauges in the A/C system, ensure the gauge hand valves are fully closed and the compressor service valves, if equipped, are in the back-seated (fully counterclockwise) position. Do not disconnect gauge hoses from service port adapters, if used, while gauges are connected to the A/C system. To disconnect hoses, always remove the adapter from the service port. Do not disconnect the hoses from the gauge manifold while connected to A/C system, as refrigerant will be rapidly discharged.

After disconnecting gauge lines, check the valve areas to be sure service valves are correctly seated and Schrader valves, if used, are not leaking.