Bang! You've been in a huge car accident, totaling both cars. But, that's weird. You have no injuries. Why's that? Then, you look at the deflated white sack coming out of the steering wheel and then you're thankful. But, how did the little bag work to save your life? An airbag provides a force over time. This is known as impulse. The more time the force has to act on the passenger to slow them down, the less damage caused to the passenger. About 15 to 20 milliseconds after the collision occurs the crash sensors decide whether or not the crash is serious enough to inflate the airbag. If the crash sensors decide to inflate the airbag, it will be deflated at about 25 milliseconds after the crash. The basic idea is that the airbag inflates as soon as the car starts to slow down in an accident and deflates as your head presses against it. That's important because if the bag didn't deflate, your head would just bounce back off it and you'd be no better off. Advanced airbags are multistage devices capable of adjusting inflation speed and pressure according to the size of the occupant requiring protection. Those determinations are made from information provided by seat-position and occupant-mass sensors. Pretty cool? We'll cover a little more next time, so go to the next post for more.