Figure 13-1. - The closed circuit refrigeration cycle.

using and handling it. At normal atmospheric temperatures, R-12 evaporates so rapidly that it freezes anything it contacts. For this reason, always wear rubber gloves and safety goggles when servicing a charged refrigeration system. Good ventilation in the working area must be ensured. Any sizable quantity of R-12 escaping into the atmosphere will displace the surrounding air and could result in suffocation. R-12 discharged near an open flame could produce a poisonous gas. Do not weld or use excessive heat of any kind near the air-conditioning system or refrigerant supply tanks. The heat will cause increased pressure inside the system and could result in an explosion. You should exercise great care to maintain the refrigerant under pressure in the supply tanks, in the air-conditioning system, and during servicing procedures.

The refrigerant must evaporate to provide a cooling effect, yet cannot be allowed to escape into the atmosphere. R-12 must circulate through a closed system (fig. 13-1), just as coolant circulates through the engine cooling system. R-12 is available in tanks and cans. The disposable can is the most convenient refrigerant container and it is widely used for servicing