Unit 3 & 4
Hydrogenated fluorocarbon(HFC)|A refrigerant that contains no chlorine atoms in its structure, which makes this group of refrigerants the most environmentally friendly of the three classifications of halocarbon refrigerants.
Miscible|Having the necessary properties to mix with or dissolve into another material. A number of refrigerants, for example, are quite miscible in refrigeration oil.
Near-azeotrope|A zeotrope with azeo-tropic properties. The refrigerant HFC-410A is an example of a near-azeotrope. Like zeo-tropes, near-azeotropes exhibit glide characteristics but they are usually minimal to the point that they are not a factor for technicians to consider when servicing a unit containing such a refrigerant.
Ozone depletion potential(ODP)|A meausre of a substance's ability to deplete atmospheric ozone that is expressed as a number. CRC refrigerants have greater ozone depletion potentials than HFC refrigerants.
Polyalkylene glycol(PAG)|Synthetic refrigerant oil used with HFC redrigerants. It is very hygroscopic.
Polyolester(POE)|Synthetic refirgerant oil used with HFC refrigerants. It is very hygroscopic.
Polyvinyl either(PVE)|A synthetic refrigerant oil with properties similar to mineral oils which can be used with HFC refrigerants. It has an advantage over POE and PAG oil in that it is not hygroscopic.
Pour point|A oil quality related to viscosity. It can be defined as the temperature at which oil first starts to flow. See viscosity.
Ternary blend|A blended refrigerant consisting of three refrigerants.
Viscosity|The thickness of a liquid or its ability to flow at a specific temperature.
Zeotrope| A blended refireant that never mixes chemically. As a result, it evaporates and condenses over a temperature range, called the glide.

Unit 4
Active recovery|A recovery process using a self-contained refrigerant recovery unit to draw or push the refrigerant out of the circuit.
Passive recovery|A recover process that makes use of the system's pressure and/or the system compressor to push out the refrigerant out. The refrigerant must be captured in a non-pressurized container.
Phosgene gas|A poisonous, colorless gas that can be generated by the burning of refrigerant gases. The gas has an odor much like that of freshly cut hay. As the gas enters the lungs, it reacts with water to produce both hydrochloric acid and carbon monoxide. Phosgene first gained notoriety as a lethal choking gas used in chemical warfare during World War I.