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The Importance of Ignition-Protected Components for Hydrocarbon Refrigerants

When designing for future refrigeration and air conditioning needs, care must be taken in the selection of components used in equipment employing hydrocarbon refrigerants such as propane (R290) and isobutane (R600).

A row of supermarket freezers filled with all types of refrigerated food.

November 5, 2019

Selecting an air conditioning or refrigeration system refrigerant is more difficult now due to the worldwide elimination of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and the restricted use of hydrofluorocarbons (HFCs). Based on new environmental regulations, the heating, cooling and refrigeration industry (HVAC-R) started to move away from ozone-depleting, greenhouse gas-producing chemicals in the late 1980s and early 1990s, creating a need for replacement refrigerants.

Attention soon turned toward alternatives with a low global warming potential (GWP). The refrigeration industry chose to focus on hydrocarbon refrigerants not only for their environmental friendliness but also for their excellent thermodynamic performance. However, hydrocarbon refrigerants are not without their own risks.

“The new substances under consideration are either flammable or operate under very high pressure,” said Brian Rodgers, a principal engineer with UL’s HVAC/R division. “Because these hydrocarbon refrigerants are highly flammable gases, care must be taken in the selection of components for use in equipment utilizing hydrocarbons in its system.”

Choose wisely

UL formed a Flammable Refrigerant Joint Task Group in 2011 to develop specific requirements for the use of low GWP, flammable refrigerants. One area thoroughly examined by the group involved the components used to manufacture an HVAC-R product.

In products utilizing CFCs, HCFCs or HFCs, a refrigerant leak would simply escape into the atmosphere as it was nonflammable and would not cause a fire.

But, as Rodgers explained, in low GWP, flammable refrigerants, switches, lights, timers and control valves could emit a tiny spark when turned on, potentially setting off an explosion if there is a leak in the refrigeration system.

For products using flammable refrigerants, the design must be constructed so that any leaked refrigerant will not flow or stagnate near ignition sources, such as an electrical component.

“Enhanced requirements are applied to the refrigerant tubing, joints and fittings on equipment having a flammable refrigerant, to reduce potential sources of leaks by minimizing the number of joints and additional protection from physical damage,” Rodgers said.

Ignition-protected components

To assist the industry in the selection of components for use in systems utilizing these refrigerants, UL has created a category for components to go through modified hazardous locations testing. “It’s not full HazLoc certification,” said Krzysztof Rymarksi, a staff engineer with UL, “but for the use of refrigerants in this application.

The testing assesses components that may potentially set off a chain reaction.

“We evaluate each component and its striking element,” Rymarksi said. “We also have an aging procedure that exposes the device to a long period of heat and sometimes, depending on the test, humidity, that could degrade the plastics.”

Other tests include submerging the device underwater to look for air bubbles, a sign that it’s not airtight, and evaluating the arcing of the components.

Related | Testing specifications for low GWP, flammable refrigerants

In addition to testing services, UL offers follow-up services to verify the continued safety of components and a database to locate components that comply with the safety standards for HVAC/R equipment.

“We’re trying to prevent the worst-case scenario,” Rymarski said. “We want to help make the use of flammable refrigerants as safe as possible.”

In any business, it’s essential to work with someone you can trust. Visit to learn more about UL’s hazardous locations equipment testing.