Airbags do not deploy in every crash; impact speed and severity decide

Airbags are counted among the most important safety features when travelling in a car. Many people assume an airbag will open automatically the moment an accident happens and save the occupants. In reality, an airbag does not open in every accident.

Whether an airbag opens depends on several factors: the speed of the vehicle, the severity of the impact, the direction from which the collision occurred and what information the car's sensors recorded. It is therefore important to understand when and how an airbag actually works.

The first question is at what speed of impact an airbag opens. There is no single fixed speed for every car. Generally, an airbag is more likely to activate in a serious head-on collision. Even so, it cannot be said that an airbag will open just because the vehicle was travelling at 30, 40 or 50 km/h.

For example, even at low speed, an airbag may open if the vehicle hits a hard object with great force. Conversely, in some minor collisions at higher speed the airbag may not open. The reason is that the car's sensors assess the sudden change in speed caused by the impact, and its severity.

Consider how an airbag opens within a few milliseconds. A car is fitted with an airbag control unit and special crash sensors. During an accident, these sensors detect the severity of the impact and send the information to the control unit. As soon as the collision appears serious, the control unit gives the command to deploy the airbag.

The airbag's inflator then starts, and the airbag inflates rapidly with the help of a special gas. The whole process can be completed in roughly 20 to 50 milliseconds. This reduces the risk of the head and chest of the driver or passengers striking the hard parts of the car directly.

So why does the airbag not open in every accident? It will not necessarily activate for every collision. In a rear-end collision, a minor collision, certain side impacts or a jolt to the underside of the vehicle, the relevant airbag need not open. This depends on the design of the car and the type of airbag.

Importantly, the seat belt and the airbag are both safety systems designed to work together. Wearing a seat belt is essential even when there is an airbag. If the seat belt is not worn, there is a risk of serious injury to occupants at the very moment the airbag opens.

So when buying a car, instead of looking only at the number of airbags, it is equally important to check its safety test, the type of airbags, the seat belts and the other safety features.