When rescue instructors speak of the presence of "dual-stage" airbags, they explain that one airbag can actually have two "charges" connected to it from the same inflator module. We are going to look at a video clip of a recent airbag "hot-wiring" exercise that was conducted at a University of Extrication hands-on training class in New York.
The vehicle is a late-model Dodge minivan. In this situation, the passenger frontal airbag inflator module was hot-wired to deploy the first stage of that airbag. The large frontal airbag deployed in a normal manner: fast, load, and to full inflation.
What the video clip shows is the second stage of the inflator module being deployed. By hot-wiring and firing off that charge, you see the already deployed airbag barely moving. Listen closely for the faint "pop" sound.
For this particular two-stage or dual-stage airbag in this vehicle, the second stage deployment was nothing significant. Having the second stage inflator accidentally deploy at a crash scene would actually not be an issue or a problem for responders with this particular make and model vehicle.
This demonstration shows an actual second-stage airbag inflator deployment, but also reinforces the importance of shutting down the electrical system by rescue personnel on scene.