GMC 2009 Sierra - Manual (Page 65)

What Makes an Airbag Inflate?
In a deployment event, the sensing system sends an
electrical signal triggering a release of gas from
the inflator. Gas from the inflator fills the airbag causing
the bag to break out of the cover and deploy. The
inflator, the airbag, and related hardware are all part of
the airbag module.
Frontal airbag modules are located inside the steering
wheel and instrument panel. For vehicles with
roof-rail airbags, there are airbag modules in the ceiling
of the vehicle, near the side windows that have
occupant seating positions.
How Does an Airbag Restrain?
In moderate to severe frontal or near frontal collisions,
even belted occupants can contact the steering wheel or
the instrument panel. In moderate to severe side
collisions, even belted occupants can contact the inside
of the vehicle.
Airbags supplement the protection provided by safety
belts. Frontal airbags distribute the force of the
impact more evenly over the occupant’s upper body,
stopping the occupant more gradually. Roof-rail airbags
distribute the force of the impact more evenly over
the occupant’s upper body.
Rollover capable roof-rail airbags are designed to help
contain the head and chest of occupants in the
outboard seating positions in the first and second rows.
The rollover capable roof-rail airbags are designed to
help reduce the risk of full or partial ejection in rollover
events, although no system can prevent all such
ejections.
But airbags would not help in many types of collisions,
primarily because the occupant’s motion is not
toward those airbags. See When Should an Airbag
Inflate? on page 1-59 for more information.
Airbags should never be regarded as anything more
than a supplement to safety belts.
1-61