Chevrolet 2006 HHR Owner's Manual page 66

If your vehicle has a side impact airbag for the right front
passenger and the person directly behind that passenger,
it is located in the ceiling above the side windows.
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CAUTION:
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If something is between an occupant and an
airbag, the bag might not inflate properly or it
might force the object into that person causing
severe injury or even death. The path of an
inflating airbag must be kept clear. Do not put
anything between an occupant and an airbag,
and do not attach or put anything on the
steering wheel hub or on or near any other
airbag covering. And, if your vehicle has
roof-mounted side impact airbags, never
secure anything to the roof of your vehicle by
routing the rope or tiedown through any door
or window opening. If you do, the path of an
inflating side impact airbag will be blocked.
The path of an inflating airbag must be
kept clear.