rmoore
02-06-1999, 07:35 PM
A posting from Ron Moore, Moderator
Firefighter Dwayne Hunt (chunt@bar.auracom.com) asked two interesting questions: one about airbags actually causing fires in vehicles. He also asked what happens when these new roof-mounted airbags are heated above that magic number of 300 degrees F.
There is a bit of confusion on this topic so I'd like to offer some insight.
Engineers at one airbag manufacturer, TRW, recently wrote me to provide details of what happens when a vehicle with a chemical gas generator airbag system burns.
You must note that there are now two very different types of airbag inflator units out there; chemical gas generator and stored pressure. Volvo 1999 MY vehicles have the only stored gas units now but NY 2000 will see more coming from other manufacturers.
The chemical gas generator, which is typically sodium azide, heats up as the passenger compartment burns. I found out that an undeployed airbag is designed to inflate in a normal manner if these chemicals sealed inside the individual airbag modules reach a temperature above 280 degrees. This intentional "auto ignition" is to keep the airbag canister from over-pressurizing.
In situations where responders arrive at the scene of a working vehicle fire, particularly one burning in the passenger compartment, the airbag gas generators, after several minutes, will reach 280 degrees and ignite, causing the airbags to deploy.
There has been at least four "rare exceptions" to the rule; one documented case recorded on videotape of an airbag module failing during a vehicle fire.
The incident occurred in the driveway of a home in Long Island NY. As the engine crew stretched their still uncharged hoseline, the airbag inflator of the burning car exploded violently, flew through the glass sunroof and landed on the driveway behind the car.
Use caution and get your gear on!
Firefighter Dwayne Hunt (chunt@bar.auracom.com) asked two interesting questions: one about airbags actually causing fires in vehicles. He also asked what happens when these new roof-mounted airbags are heated above that magic number of 300 degrees F.
There is a bit of confusion on this topic so I'd like to offer some insight.
Engineers at one airbag manufacturer, TRW, recently wrote me to provide details of what happens when a vehicle with a chemical gas generator airbag system burns.
You must note that there are now two very different types of airbag inflator units out there; chemical gas generator and stored pressure. Volvo 1999 MY vehicles have the only stored gas units now but NY 2000 will see more coming from other manufacturers.
The chemical gas generator, which is typically sodium azide, heats up as the passenger compartment burns. I found out that an undeployed airbag is designed to inflate in a normal manner if these chemicals sealed inside the individual airbag modules reach a temperature above 280 degrees. This intentional "auto ignition" is to keep the airbag canister from over-pressurizing.
In situations where responders arrive at the scene of a working vehicle fire, particularly one burning in the passenger compartment, the airbag gas generators, after several minutes, will reach 280 degrees and ignite, causing the airbags to deploy.
There has been at least four "rare exceptions" to the rule; one documented case recorded on videotape of an airbag module failing during a vehicle fire.
The incident occurred in the driveway of a home in Long Island NY. As the engine crew stretched their still uncharged hoseline, the airbag inflator of the burning car exploded violently, flew through the glass sunroof and landed on the driveway behind the car.
Use caution and get your gear on!