The failure of safety–critical systems can lead us to huge damage and catastrophic consequence. Airbags are such safety–critical systems whose failure can create a lot of trouble for human life or sometimes even death. These systems should be highly reliable and designed with great precision. In this paper, the reliability of airbag is computed using failure rate of sensors by modeling it into petri net. These are tested on three vehicle models SUV, pickup truck, and van. The bumper guard absorbs the jerk in case of vehicle collision which prevents the sensors to receive the impact of the collision, resulting in airbag non-inflation. When the bumper guard is used the reliability of deploying the airbag system is decreased by 9.91% to 50%, depending upon the velocities of the collision.