Using flammable refrigerants in an automotive air conditioning system is prohibited by law. However, there are certain exceptions, such as the R1234yf refrigerant, which is only mildly flammable in specific conditions. Additionally, flammable refrigerants are permitted in trailer refrigeration units for heavy-duty trucks. Nonetheless, it is crucial to note that flammable refrigerants must never be used in a car or light truck A/C system except for the specified exceptions.
The Potential Fire Risks By Flammable Refrigerants
Hydrocarbon mixtures and blends, such as propane and butane, can function effectively as refrigerants and provide cooling characteristics comparable to R-12, R-22, and R-134a. However, if the evaporator within the passenger compartment develops a leak, the flammable vapor may create a potential fire or explosion hazard. Is risking your life while driving your vehicle worth it?
Furthermore, consider the consequences if your vehicle is involved in an accident. The A/C condenser in front of the radiator contains high-pressure refrigerant vapor and liquid. In the event of a frontal collision (which is common), rupturing the condenser will release high-pressure flammable vapor, almost guaranteeing an underhood fire.
Using a cheap flammable refrigerant in your vehicle’s A/C system may jeopardize your life or the lives of your passengers. R-134a is the sole refrigerant suitable for recharging a modern automotive A/C system.
EPA SNAP Rules on Flammable Refrigerants
The regulations set by the US EPA SNAP prohibit flammable refrigerants in vehicles. The sole exception is HFO-1234yf, a new refrigerant that is only mildly flammable in specific circumstances.
Furthermore, the Mobile Air Conditioning Society (MACS) and the Society of Automotive Engineers (SAE) do not endorse the use of flammable refrigerants. Similar to the EPA SNAP guidelines, the only exception is the HFO-1234yf refrigerant, which will begin to replace R-134a in some new cars in 2013 or later.
Use Only R-134a Refrigerant
The EPA, MACS, and SAE concur that R-134a is the only acceptable replacement refrigerant for newer R-134a systems. Using anything else may result in cross-contamination issues and cooling performance problems. For older vehicles that use R-12, retrofitting with R-134a or other authorized alternative refrigerants (that are not flammable) is possible.
Although the document I am sharing is from 1999, it includes valuable information regarding alternative refrigerants. The basic information remains unchanged, and the only update is the approval of HFO-1234YF for future A/C systems.
The Use of Flammable Refrigerants is Prohibited by Law
Several city municipalities and states have implemented regulations that prohibit the use of flammable refrigerants in vehicles.
In Europe, propane is authorized for use in some home refrigerators. However, the quantity permitted is minimal, eliminating the risk of fire or explosion. Refrigerators must also pass safety tests, ensuring that refrigerant leaks do not create a potential fire or explosion hazard.
Flammable Refrigerants: OZ-12 and HC-12A
Alternative refrigerants like OZ-12, HC-12a, R-176, and R-405a do not meet the EPA’s environmental acceptability or safety standards. Flammable refrigerants such as OZ-12 and HC-12a contain large quantities of hydrocarbons, such as propane, butane, and isobutane, and have been deemed unlawful for use in mobile A/C systems. However, due to their inexpensive cost, they are still being utilized in A/C systems.
The EPA does not authorize flammable refrigerants since they pose a significant threat to the vehicle’s occupants in the event of a leak. According to the EPA, a cigarette or spark can ignite the refrigerant, causing a fire and explosion.
On the other hand, the manufacturers of HC-12a argue that the flammability risk is overstated, and there is no evidence to substantiate claims that a cigarette or spark can ignite their product. They also argue that the EPA’s stance on their product is unjustified and that HC-12a has been employed in many vehicle A/C systems worldwide without any reported accidents or injuries resulting from the ignition.
HFC-152a Refrigerant
HFC-152a, an alternative refrigerant proposed for automotive use, has a GWP rating of 140, meeting European global warming requirements. It also has similar cooling characteristics to R-134a and could be a direct substitute with little modification. However, it is currently illegal due to its flammability.
One potential solution to address the flammability issue is installing a leak sensor inside the vehicle that alerts passengers of a leak and automatically opens the power windows to vent the vapors, reducing the risk of fire or explosion.
Another solution is redesigning the A/C system with a “secondary loop” that keeps the flammable refrigerant in the engine compartment rather than the passenger compartment. In this approach, the refrigerant flows through an intermediate heat exchanger. It cools a liquid (such as a water/antifreeze mixture) that circulates through the HVAC unit inside the vehicle. The U.S. EPA recently reported that this method meets its safety criteria while remaining energy efficient. However, it still poses a risk to technicians and DIYers during A/C system recharging and servicing and does not reduce the risk of fire in a frontal collision.
R-1234YF Refrigerant
R1234yf is the latest alternative refrigerant that replaced R-134a on some vehicles starting in the 2014 model year. Its thermal properties are comparable to R-134a, so minimal modifications to the A/C system are needed, such as a larger condenser and using different PAG oil. The refrigerant has a low GWP rating of 4, which satisfies European regulations for decreasing global warming. However, it is only slightly explosive, with a much lower risk than HFC-152a, and will only ignite under specific conditions that are not expected to occur in typical automotive use.
Volkswagen Avoid HFO-1234yf Refrigerant
Volkswagen has stated that it will not be using HFO-1234yf refrigerant due to concerns about its safety. The company worries that the refrigerant may ignite in real-life conditions inside a vehicle. Instead, Volkswagen is currently considering CO2 as the best alternative to R134a. This decision follows a similar announcement by Daimler (Mercedes Benz) to abandon HFO-1234yf in favor of CO2 or other alternative refrigerants. According to tests conducted by Daimler, HFO-1234yf can be ignited by a spark within seconds of its release and emits highly toxic fumes and acids as it burns. CO2, on the other hand, is nonflammable and carbon neutral. As a result, it appears that HFO-1234yf is currently on hold for two of the leading German automakers.
New update:
According to SAE International, after conducting extensive testing and review, they have determined that Honeywell’s new mobile air conditioning refrigerant, HFO-1234yf, which has a low-global-warming-potential, is safe for use in passenger car A/C systems. Although HFO-1234yf can be flammable under certain conditions, SAE has concluded that these conditions are highly improbable to occur in a real-world crash.