As a rule, an airbag consists of a polyamide fabric with an inside lining. It should be filled with nitrogen gas to a pressure of 0,05 bar in about 0,05 seconds (50ms), depending on the impact deceleration rate. The accompanying gas generator is ignited either by the still intact vehicle electrical system, or by a short-time electric accumulator (e.g., a condenser). At the point of full impact (e.g., the head) the pressure amounts to about 0,6 bar.
Given that an inflated airbag would hinder any rescue operation, the calculated pressure loss is almost as important as the inflation. The one in the above picture has, for this reason, at the back of the impact side, suitable openings. Unfortunately, the incredibly fast processes are not possible without a certain amount of heat developing. Hybrid generators avoid this by mixing a smaller portion of the solid propellant with the, up to 500 bar pressurised cold gas (mostly Argon), which is kept in a small steel container.
There are, by the way, still those who believe, that in the case of an accident, they can absorb the impact force with their (strong) upper arms. This is why some believe, they can do without the safety belt. Wishful thinking I'm afraid. At an impact speed of only 11 km/h this is generally no longer possible. At 50 km/h, the force to be absorbed would amount, even with a relatively light body-weight, to more than 1 ton. This would be like having a compact-car placed on your back when lying in the push-up position. At 100 km/h, it corresponds to a fall from a height of about 40 meters. 11/08