airbag

While ammonium nitrate may be the key culprit behind the Takata airbag ruptures, two other factors have been identified, Automotive News reports. The Independent Testing Coalition (ITC), a consortium of 10 automakers, have found that three elements including the now-notorious ammonium nitrate compound, will lead to the airbag rupture, when combined.

According the ITC, the second element was the inflator assembly itself, which could not keep moisture out effectively. The third element meanwhile, was humidity and temperature changes. Exposure to high-humidity and repeated temperature fluctuations will, over time, cause the ammonium nitrate to combust and rupture the inflator when the airbags deploy.

All three (ammonium nitrate, construction of the inflator assembly and exposure to heat and humidity), form the recipe for disaster. “You can’t have the energetic disassembly without all three factors. You have to have all three,” said David Kelly, head of the ITC and former chief of the National Highway Safety Administration (NHTSA).

SRS-Airbag

While the elements may have been highlighted before, this is the first time that a conclusive root cause has been laid out. The tests were carried out by Orbital ATK, an aerospace and defence contractor, with expertise in rocket propulsion systems. Takata has acknowledged that the findings by Orbital and ITC were consistent with its own and that by German research organisation, Fraunhofer Group.

The NHTSA is currently reviewing the findings by the ITC. That said, while the investigations by the ITC took about a year and involved roughly 2,000 inflators from recalled vehicles, the new batch of inflators used by Takata in their own recall expansions recently and the ammonium nitrate inflators with desiccant (a chemical drying agent) have yet to be tested.

This, according to Kelly, will be the next phase of its investigation. Although 12 major automakers have announced their departure from Takata, the list of vehicle recalls continues to grow around the world. The NHTSA has said previously, that tens of millions of vehicles with inflators containing ammonium nitrate will be recalled by 2018 if Takata cannot prove that they are safe.