Chemical provider, Honeywell, says it remains concerned with the protocol used in German road safety authority (KBA) tests on its much-discussed r1234yf air-conditioning refrigerant, describing one process used as "farcical." 

Honeywell is standing by the safety properties of its r1234yf coolant, despite Mercedes-Benz claims it can be highly flammable in certain conditions, but has raised questions as to the methodology employed by the KBA (Kraftfahrt-Bundesamt).

"We have not had any visibility on the test process - our concern is more around what is the test protocol - we have had no [KBA] response," Honeywell Fluorine Products Europe, Middle East, Africa and India managing director, Paul Sanders, told just-auto from Brussels. "We are surprised we [have] not been given the opportunity."

Mercedes, the European Commission (EC) and France, have taken radically opposing views as to the safety of rival r134a and r1234yf refrigerants, with the German automaker's use of the former leading to a blockade of its A, B, CLA and SL models that has seen around 5,000 vehicles banned from certification by authorities in Paris.

The KBA issued a preliminary report into its r1234yf tests last week with final publication due this autumn, but all sides are claiming various levels of vindication for their positions within it.

"We have seen the report - the results are not surprising in they confirm the product [r1234yf] can be used safely," said Sanders.  "[It] does not pose any different risk in the car industry.

"The bit that is puzzling is we have looked at the public announcement and have not had any feedback on the testing. We did formally request transparency."

Sanders added there were several layers of tests involved to evaluate flammability, but described as "farcical," and "spurious," a level three process which he speculated might have involved a catastrophic hose failure with "rather strangely" increased engine temperature.

"They increased temperature to a level that does not even exist today," said Sanders, adding: "This is our concern. The risk of these events happening is as close to zero."

Sanders added the EC had written to the German Transport Ministry concerning its adoption of the European Mobile Air Conditioning directive and was now waiting for Berlin's response.

The KBA in Germany was not immediately available for comment.