Pure R-12 (CC12 F2 ) is colorless. It is odorless in concentrations of less than 20 percent by volume in air. In higher concentrations, its odor resembles that of carbon tetrachloroethylene (dry-cleaning fluid). It has a boiling point of - 21.6F at atmospheric pressure. At a room temperature of 70, R-12 is a liquid, provided it is kept at a pressure of at least 90 psig.

In either the liquid or vapor state, R-12 is nonflammable and nonexplosive. It will not corrode the metals commonly used in refrigerating systems.

Because it does not decompose, R-12 is a stable compound capable of undergoing the physical changes required of it in refrigeration service. It is an excellent solvent and has the ability to loosen and remove particles of dirt, scale, and oil with which it comes in contact within a refrigerating system.

Other refrigerants, such as R-22 (CHC1F2 ) and R-11 (CC13 F), are colorless, nonexplosive, and nonpoisonous. These refrigerants have many properties in common with R- 12; however, their operating characteristics are different.

SAFETY PRECAUTIONS

Personnel working with refrigerants may be injured or killed if proper precautions are not taken.

HALOCARBONS

Refrigerants are halocarbons, which are organic chemical compounds containing hydrogen and one or more atoms of carbon, fluorine, bromine, chlorine, or iodine. These substances may be present in various combinations in the compound.

Familiar brand names of refrigerants include Freon, Gentron, Gension D., or Frigen. Working with these compounds regularly aboard ship will make it easy for you to gain a false sense of security. This may tempt you to forget about the potential hazards of halocarbon refrigerants. Remember: Halocarbon refrigerants are especially dangerous when used in high concentrations in confined or poorly ventilated spaces.