There is much confusion and ignorance about front air bags and when they are supposed to deploy. Airbags are supposed to explode in the first .05 seconds of a frontal impact. There is a control module that provides feedback as to whether the crash is severe enough to cause airbag deployment. Many do not know, but the front impact must damage or hit  enough of the sensors to  create the  deployment- usually it must be a moderate to severe impact.  As well, an  off to the side of the front hit may not cause deployment. Crucial sensors gather information such as who is wearing a seatbelt, the car’s speed, the car’s acceleration or de-acceleration, and many other factors. For important airbag information I recommend reviewing the websites of the  Insurance Institute for Highway Safety,, and the National Highway Traffic Safety Administration,