Ford 1996 Bronco Manual page 32

The following four steps show how the air bag
system works:
1. Sensors in the vehicle will detect the degree
of severity of a frontal impact. When the
sensor system is activated, electric current
flows to the inflator and the system ignites
the gas generant.
2. The propellant then rapidly burns in the
metal container. The rapid burning produces
nitrogen gas and small amounts of dust. The
nitrogen gas and dust are cooled and filtered
during inflation of the air bag.
3. The inflating supplemental air bag splits
open the trim cover. The supplemental air
bag then rapidly unfolds and inflates in front
of the driver.
NOTE: STEPS 1-3 TAKE PLACE IN A
FRACTION OF A SECOND.
4. After inflation, the gas empties through holes
in the air bag. The air bag deflates at once.
The surface of the air bags and the vehicle
interior may be dusted with a powdery residue.
The powder is cornstarch or talcum powder,
which is used to lubricate the air bag as it
inflates, and sodium compounds such as sodium
carbonates (e.g., baking soda), and possibly a
very small amount of sodium hydroxide that
may be irritating to the skin and eyes, but is not
toxic.
Right after air bag inflation, you may notice
smoke (from the powder and dust) and smell
the burnt propellant. This is normal.
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