An airbag wins by failing on purpose. It inflates so fast it feels almost violent, yet its entire design goal is to disappear under you in the next split second. Gas generators fire, fabric snaps open, and then the system starts throwing away the very gas it just created.
Engineers treat that first instant as non‑negotiable. About 30 milliseconds after a severe impact, a pyrotechnic inflator converts solid propellant into high‑pressure gas, driving the bag outward before your torso can surge forward under inertia. Impact biomechanics and crash test dummies define the pressure curve: enough internal force to catch a head and chest, not enough to break ribs.
The counterintuitive part is the leak. Fixed vent holes and porous weave act as a controlled orifice, a kind of built‑in pressure relief valve that shapes the deceleration pulse your body feels. As your mass loads the cushion, gas escapes, the internal pressure drops, and the bag collapses in step with your motion, trimming neck forces and chest compression. What looks like a violent balloon is, in practice, a timed pressure regulator wrapped in nylon.
