Hummer 2004 H2 Owner's Manual page 391

The accessory inflator hose also has a built-in air
pressure gage. As soon as you start to inflate an object
it will automatically read the current pressure.
Press and release the switch to turn the accessory
inflator on. The indicator light will remain on while the
inflator is running. Press and release the switch to
turn the inflator off. Place the inflator kit tools and the
hose in the pouch and store it back in the spare
tire cover pocket.
If your vehicle is equipped with the air suspension
system, load leveling will not function with the inflator
hose attached to the inflator outlet.
CAUTION:
{
Inflating something too much can make it
explode, and you or others could be injured.
Be sure to read the inflator instructions, and
inflate any object only to its recommended
pressure.
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