1,1,1,2,2-Pentafluoroethane

1,1,1,2,2-Pentafluoroethane, also called simply pentafluoroethane, HFC-125, or R-125, is a refrigerant that has zero ozone depletion potential. It has the formula CF3CHF2.

Pentafluoroethane in an azeotropic mixture with difluoromethane is known as R-410A, a common replacement for various chlorofluorocarbons (aka Freon) in new refrigerant systems.

Pentafluoroethane is also used as a fire suppression agent in fire suppression systems.

Fire suppression systems
HFC-125 can be used in clean agent fire suppression systems. The HFC-125 clean agent is stored in a pressurized container and introduced into the hazard as a gas. The agent is odorless, colorless, electrically non-conductive, non-corrosive, and leaves no residue. It is used in occupied enclosed areas that contain high-value assets.

HFC-125 suppresses fire by absorbing heat energy at its molecular level faster than the heat can be generated, so the fire cannot sustain itself. It also forms free radicals to chemically interfere with the chain reaction of the combustion process. This makes it a highly effective fire fighting agent that is safe for people and causes no damage to equipment.

When introduced to the market HFC-125 was not considered safe for use in occupied spaces. The US EPA SNAP (Significant New Alternative Policy) listing reflected this. Following the introduction and acceptance of the PBPK model in the NFPA standard NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems 2004 Edition, the restriction was relaxed and now HFC-125 can be used in occupied hazards. Generally, class B (flammable liquid) hazards require concentrations that exceed the agent NOAEL so extra precautions must be taken to avoid prolonged exposure to the agent.