Airbag is a very important safety device. It protects the occupant in all types of crashes like front and side crash. But the car manufacturer and airbag developers have the biggest challenge to control the explosion for protecting the human life.
It is a controlled explosion. If the explosion is not controlled, it can kill the person. A driver airbag releases a force of 7kN to 9 kN and a passenger airbag release the force of approximate 13kN to 15kN at the time of deployment. This force can vary depending on the airbag size and ventholes opening.
This force is sufficient to break the neck of a human if he comes in contact at the time of deployment. Instead of protecting, it can cause a serious head or neck injury and can kill the occupant.
The airbag producers are very careful while designing and developing it and make several tests to check the sensors and algorithms.
Despite of taking extra cares and several testing, the design error occurs. Here one can see a well-recognized, company like Takata must replace their airbags. At the time of deployment, the airbags are exploding when the car is exposed to heat and humidity for a longer time. This causes the casualty instead of saving the life in crash. The actual design problem is still unknown, but National Highway Traffic Safety Administration NHTSA believe a faulty seal on the inflator is causing the explosion uncontrolled and killing the occupants.
Approximate tens of millions of vehicles are under recall list of National Highway Traffic Safety Administration NHTSA. This is a very big set back to Takata as well to OEMs.
Here it is important to know that even, a correctly designed airbag also needs to be optimized by car manufacturer, based on the front and side structural stiffness of the car body. If the airbag is not optimized, even a good airbag cannot protect the occupant. As a occupant safety engineer, we allow the occupant to come in contact to fully deployed airbag at a specific time.
That’s the reason occupant safety has the maximum weightage in all the NCAPs.  
To know more about airbag optimization and BIW stiffness