GMC 2008 Yukon Denali Owner's Manual page 80

Airbags are designed to supplement the protection
provided by safety belts. Even though today's airbags
are also designed to help reduce the risk of injury
from the force of an inflating bag, all airbags must inflate
very quickly to do their job.
Here are the most important things to know about the
airbag system:
CAUTION:
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You can be severely injured or killed in a crash
if you are not wearing your safety belt — even
if you have airbags. Wearing your safety belt
during a crash helps reduce your chance of
hitting things inside the vehicle or being
ejected from it. Airbags are "supplemental
restraints" to the safety belts. All airbags are
designed to work with safety belts, but do not
replace them.
1-76
CAUTION:
{
Frontal airbags are designed to deploy in
moderate to severe frontal and near frontal
crashes. They are not designed to inflate in
rollover, rear crashes, or in many side crashes.
Rollover capable roof-rail airbags are designed
to inflate in moderate to severe crashes where
something hits the side of your vehicle, during a
vehicle rollover, or in a severe frontal impact.
They are not designed to inflate in rear crashes.
Everyone in your vehicle should wear a safety
belt properly — whether or not there is an
airbag for that person.