When the temperatures warm up, it's a good time to remind technicians and drivers about the dangers associated with hydrocarbon refrigerants being sold as cheap substitutes for R-134a and R-12.

Marketed under names like HC-12a, OZ-12, DURACOOL 12a, and EC-12a, these hydrocarbon blends may contain high quantities of propane, isobutane, and other highly flammable gases.

"These products are sold online and at flea markets as direct replacements for SNAP-approved refrigerants," says Gary Hansen, vice president of Red Dot Corp. Based in Seattle, Red Dot designs and manufactures heating and air-conditioning systems, components, and replacement parts for heavy trucks and other commercial vehicles.

SNAP (Significant New Alternatives Policy) is a U.S. Environmental Protection Agency program that evaluates a refrigerant's ozone-depleting potential, global warming potential, flammability, and toxicity. The EPA has banned hydrocarbons as a replacement for R-12 in motor vehicles. Many states have made them illegal.

"Many consumers aren't aware of the hazards these cheap hydrocarbon blends pose to themselves and technicians who service their vehicles," Hansen says.

Hydrocarbon blends are highly flammable and in a confined space may burn or explode in the presence of an open flame, spark, or cigarette. No vehicle manufacturer has endorsed or authorized the use of hydrocarbon refrigerants in its current-production A/C systems, according to Red Dot. They can degrade gaskets and hoses designed for R-134a or R-12, making leaks more likely. Use them and you'll void the warranty.

Technicians should check for A/C system leaks before making an inspection or repair that requires an ignition source (or may generate one). "Use well-maintained, properly calibrated tools to identify refrigerants and sniff for leaks," Hansen adds.

"If you service A/C systems, test for these refrigerants and educate your customers about the dangers of flammable hydrocarbon refrigerants so they know to avoid them," Hansen says. "If you operate a motor vehicle and notice decreased A/C performance, stay away from cheap 'substitute' refrigerants and contact a certified and experienced mobile HVAC technician. He'll have the expertise and equipment to diagnose the problem and address it."

For more information, the EPA has a web page devoted to questions about these refrigerants here. For a list of acceptable substitutes, click here.