As part of a routine test of a new refrigerant being used in the Mercedes-Benz B Class, engineers simulated a pinhole leak in a coolant line. When the refrigerant (now mixed with A/C compressor oil) sprayed on a hot engine, the results were dramatic.

The vaporized mixture reportedly ignited on contact with the hot surface, creating what Reuters (via Yahoo News) described as a “ball of fire,” followed by a cloud of dangerous hydrogen fluoride gas. The corrosive gas then attacked the windshield, etching the glass and raising even more potential concerns about the safety of the new HFO-1234yf  refrigerant.

The team of manufacturers within the SAE International group evaluating the new refrigerant's safety includes Audi, BMW, Chrysler/Fiat, Daimler, Ford, General Motors, Honda, Hyundai, Jaguar Land Rover, Mazda, PSA, Renault and Toyota. To date, only Daimler's testing has found any concern with the refrigerant's safety.

"Honeywell continues to believe that SAE International’s latest evaluation will only reconfirm the overwhelming body of data--including rigorous and comprehensive studies conducted in Europe, the U.S. and Japan--that have clearly and repeatedly determined that HFO-1234yf is safe for use in automobiles,” said Dr. Ian Shankland, chief technology officer for Honeywell Performance Materials and Technologies.

Refrigerant, after all, was never viewed as a volatile or toxic chemical, and manufacturer Honeywell (with partner Dupont) was quick to point out that Mercedes’ tests did not simulate actual crash conditions. In fact, cars that were crash tested showed no potential problems with the HFO-1234yf refrigerant and combustion.

At stake is a huge amount of business for Honeywell and Dupont, as the manufacturers have spent serious money designing, developing and producing the refrigerant, which is the only material to meet new EU climate guidelines. As of January 2013, the current gas, R134a, will be phased out over greenhouse gas concerns.

By 2017, every car produced for sale in Europe (about 14 million, annually) could be filled with HFO-1234yf refrigerant, resulting in nearly a billion dollars in annual revenue for Honeywell. The Mercedes-conducted tests, if proven valid, could jeopardize (or at the very least delay) the rollout of the new gas.

In September, Daimler notified EU authorities that it wanted to recall all 1,300 cars already built with HFO-1234yf refrigerant, prompting 13 other automakers to begin a new round of safety tests on the gas, with results still pending.

For its part, Honeywell claims that HFO1234yf is only “mildly flammable,” and that Mercedes-Benz rigged the test to achieve the desired result. The reason? To delay the implementation of HFP-1234yf in its vehicles, as it costs ten times what the current R134a refrigerant does.

Furthermore, Honeywell is quick to point out that airbags, often seen as adding to vehicle safety, pose more of a threat to occupants than its new coolant. Said Chris Seeton, a Honeywell engineer leading the development of HFO-1234yf, “The chance of being killed by an inflating airbag is 100  times higher.”

Who’s right and who’s wrong is still being sorted out, but it’s likely that the phase-in of HFO-1234yf won’t begin as scheduled in January of 2013. Depending upon which manufacturer you believe, that’s either a very good thing or a very bad thing.