HC-12a

HC-12a, also called ES-12a, OZ-12a, DURACOOL 12a^[1] and Hydrocarbon Blend B, is marketed as a "drop-in" replacement refrigerant for R-12 and other refrigerants. HC-12a is a mixture of hydrocarbons, specifically propane (R-290) and isobutane (R-600a), and is therefore considered nearly non-ozone-depleting. The hydrocarbon blend is compatible with hoses and oils used in R-12 systems.

As it is flammable, it is illegal for use as an R-12 replacement in the United States.^[2][3] Its use in public transport vehicles has also been illegal in the United States since 1990.^[4][5]

This hydrocarbon blend caused^[6] of the Tragedia de La Cresta [es] in October 2006,^[7] a bus fire which killed 18 people and injured 25, some severely, which in turn led to an overhaul of Panama City's public transport system.^{[5][8][9][10]} The refrigerant ignited due to an electrical spark^[11] which followed a refrigerant leak,^[12] which quickly set the bus ablaze as the fire spread from the refrigeration system towards the interior of the bus.^[13][5][4] The bus lacked emergency exits and fire extinguishers, and the occupants' peril was aggravated by the location of the engine and the refrigeration system compressor—below a cover on the inner side of the only passenger exit door.^[14] A lawsuit in a US court against Northcutt, which imported the HC-12 involved in the tragedy, and OZ technology, Inc., which manufactured the HC-12^{[11][6][15][16][17]} began in 2008; in 2018, Northcutt reached a settlement with the victims of the tragedy and their relatives.^[5][18][19]