Knowledge is protection
by Jacques Gordon. Managing editor, ACTION Magazine
You’ve probably heard about the air bag recall. Toyota, Honda, Nissan and Mazda are recalling over 3 million 2000 to 2004 models to repair air bag systems. The problem is in the inflator, which is reported to have “burst” in several vehicles and sent plastic shrapnel flying through the cabin. No injuries have been reported as a result of this issue.
The affected systems all came from Takata Corporation, which supplies air bags and seat belts to automakers around the world. Takata is an industry leader, an innovator with state-of-the-art R&D facilities, and they recently won awards for a new child seat design. The faulty airbags are reported to be from Takata’s plant in Mexico. A Honda spokesperson said the problem was caused by human error that allowed “defective products and parts (that) were improperly stored” onto the production line.
Air bag inflators are a pyrotechnic device. In earlier systems, the fuel is sodium azide, a type of salt that is stable when handled properly but explodes under impact. When ignited it burns quickly, producing nitrogen gas and sodium oxide powder. According to the MSDS, it forms a nasty poison when dissolved in water that can be fatal just through skin contact, but after ignition it is no longer toxic.
In newer air bag systems, the most common fuel is nitroguanidine, and the inflator assembly includes “burn rate modifiers” to control the deployment rate of the air bag. Nitroguanidine also burns fast and can detonate under impact. While not toxic, it’s considered carcinogenic.
The inflator assembly on “adaptive” or “multi-stage” air bags has multiple fuel chambers, usually of different sizes. The control unit can choose which charge(s) to fire, enabling it to deploy the air bag at different speeds according to the severity of the crash.
Air bags are housed behind steering wheel covers, dashboard covers or another part of the vehicle’s interior. Takata and other manufacturers design (and often manufacture) special materials for these covers to make sure they open properly without impeding air bag inflation. If air bag deployment is too forceful, it may shatter the cover.
None of the manufacturers involved in this recall are providing technical details, but the recall is to replace the air bag inflator, or the whole air bag assembly if the inflator is not a separate piece. An aftermarket shop performing this recall should carefully follow the instructions provided in the factory service information, and ship or dispose of the old air bag assembly according to local hazmat regulations.
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