Honeywell Defends R1234yf Refrigerant Against Daimler

Video screen capture.

R1234yf. Remember that, because this is the hottest front in the battle for climate control.

The current refrigerant R134a -- if released in a crash or due to illegal end-of-life disposal -- contributes over 1400 times more to global warming than CO2. R1234yf drops that factor to 4.

Daimler bashed the environmentally friendly coolant with a shocking video, made public by Germany's Autobild. The video shows a coolant leak exploding into flames on contact with hot surfaces under the engine hood. The public will see the flames and read about toxic hydrogen fluoride releases. The scientist sees question marks: does this video represent a "real-life" test?

The Americans for Limited Government posted the video in a campaign against (now) EPA chief Gina McCarthy, who approved the coolant in American cars while in her former position at EPA.

So here's the facts you need to know when the topic comes up at the next dinner party.


After Daimler started the air conditioning debate, Honeywell has come to the defense of R1234yf. The information provided to TreeHugger will not settle the matter. A lot of the information relies on highly technical analysis, but here are the simple facts that anyone can understand:

  • Everyone who analyzed the safety of R1234yf already knew it can ignite on contact with very hot surfaces, around 700 - 800 °C (1290 - 1470°F).
  • Even with this knowledge, safety analysts estimate the risk of exposure to HF or fire due to an R1234yf ignition event at 100,000 times less likely than a vehicle collision due to brake failure.
  • People who don't lose sleep worrying about brake failure will still have doubts about R1234yf now that a video of a flaming engine compartment has excited the passions.

So how is it possible that Daimler's simple test shows a nightmare scenario but the experts say R1234yf is safe? Is this another case of the scientists being paid off by big industry? Who can we trust?

Mercedes climate control

InSapphoWeTrust/CC BY-SA 2.0
First you should know that the studies proving the safety of R1234yf are done by an independent group, SAE International. SAE describes their mission: "SAE International is a global body of scientists, engineers, and practitioners that advances self-propelled vehicle and system knowledge in a neutral forum for the benefit of society." But in this day and age, even a neutral body can be swayed by their own mission -- anyone can see that we need better refrigerants as global warming can burn a technology just as quickly as an engine fire can start a recall.

In that front there is good news: since Daimler has flaunted Europe's law requiring the environmentally friendly R1234yf, and the German government granted them an exception to do so, the German authorities will be on the line to produce a study either supporting Daimler's position or returning R1234yf to an officially trusted status.

In the meantime, we would like to point out some further simple facts that explain the gap between SAE's "safe" finding and Daimler's scary video. First, R1234yf does ignite. But not easily. In determining that drivers and emergency responders need not fear R1234yf, SAE considered the "real-life" circumstances. There are many flammable fluids under the hood of the average car.

These do not ignite in collisions for many reasons: a collision sufficient to cause leaks also introduces a lot of air to the engine compartment, moving ignitable materials around quickly enough that they cannot contact hot surfaces long enough to start burning. Other fluids, such as steam, contribute to cooling hot surfaces. Engineering standards require that hot surfaces be heat shielded, and that areas where vapors could accumulate long enough to ignite do not exist. Also, a real-life leak from a hose would not be pre-heated (as Daimler's copper test feed tube would be) and any large volume refrigerant leak would include rapidly expanding liquid R1234yf -- further cooling contact points as well as pushing gases quickly out into the environment (again, reducing the contact time required to cause ignition).

What Daimler did in their test video is inject a pre-heated, perfect mixture of air and R1234yf into the hottest engine compartment to optimize the risk of ignition in an almost closed engine compartment. The official analysis of Honeywell engineer Dr. Chris Seeton (who was not given all of the details of the test protocol by Daimler but analyzed the video sequence) finds that Daimler's test replicates the conditions of the September 2008 test by the French INERIS group showing that R1234yf does indeed ignite exactly as Daimler's video "proves". This is therefore not new information. The risk of exposure to fire or HF -- even in light of Daimler's claims -- remains at 100,000 times lower than a brake failure collision, a million times lower than a vehicle fire by all other causes.

SAE has weighed in supporting Dr. Seeton's conclusion:

After extensive testing and analysis, the new CRP concluded that the refrigerant release testing completed by Daimler was unrealistic. Their testing created extreme conditions that favored ignition while ignoring many mitigating factors that would be present in an actual real-world collision.

Remember, the issue of the R1234yf escaping into the atmosphere in all this is still a plus for R1234yf, which will degrade naturally in the atmosphere in less than a week with far lower global warming potential than its long-lived competitors (possibly even lower than the GWP of CO2 according to a commenter at TreeHugger).

So what is the final conclusion? Does Daimler have a design problem? Are they overstating the risks because redesign will cost them far more than the 30 - 40 euros (US$39 - 51) per vehicle that the drop-in replacement costs their competitors who have reportedly been unable to replicate Daimler's results? And can the facts ever trump the inflammatory video in a concerned public's mind?

Time will tell us more. But for now, the science says: if you do not worry about events with higher probability like dying in a commercial plane flight or crashing due to brake failure, stop worrying about R1234yf.