How Airbags Work

Airbags — something nobody wants to experience in action. But in serious accidents, they offer protection. That’s why they are subjected to extreme demands during their development.

Modern cars, Škodas included, have many more airbags today than they did some years ago. The driver’s frontal airbag in the steering wheel and the passenger’s airbag integrated in the dashboard are taken for granted. Škoda cars also have side airbags, which are located in the outer sides of the seats (mainly in the front, but also in the rear) or head airbags. There are two of these for the whole car and this airbag always covers the complete area of the side windows on each side. There is also a knee airbag (typically on the driver’s side, but also on the passenger side) and a centre airbag that inflates in the space between the driver and passenger. In total, then, there are up to 10 airbags in current Škodas.

Airbag Benefits

Each of the airbags protects against slightly different risks. The frontal ones cushion the passengers’ head and chest in a frontal collision; the side and head ones protect the torso and head, especially in a side impact; and the centre airbag, which is a relative novelty, is designed to prevent the driver’s and passenger’s bodies from colliding in various impacts.

Airbag Design

The design of the airbags is always adapted to these functions. “Gradually, the developers figured out that the frontal airbags should deflate in a controlled manner when the occupants hit them, so they have a special design with vents that make this possible. On the other hand, head or knee airbags, for example, should not deflate, so they don’t have vents. The airbags are silicon-coated on the inside and, if necessary, at the seams to prevent uncontrolled gas leakage,” explains Michal Mrhálek, who deals with airbag development at Škoda Technical Development.

Airbags in Action

How an airbag inflates is determined by the shape of the bag, its specific packing and also the type of firing mechanism. “Large bags, such as the ones in front of the driver or passenger, are inflated using a pyrotechnic cartridge and a gas generator – it simply burns to generate a large volume of gas quickly. Airbags with a different design, such as head, knee or centre airbags, use cartridges with compressed gas and the principle of adiabatic expansion, or gas expansion,” says Hana Cwierzová, a specialist from Škoda Auto Technical Development.

Detecting the event that is supposed to cause the airbag to inflate is also important. “Detection is carried out by various sensors in the car, and the situation is evaluated by the control unit. This then decides which airbags should be activated,” explains another developer, Klára Ševčíková. The whole process is super-fast. It takes just a few milliseconds from the initial detection to the controlling unit’s decision, and another tens of milliseconds to fill the airbags. For example, the head airbag is full in 25 to 35 milliseconds and the driver’s airbag inflates in 30 to 40 milliseconds. Depending on the type of collision, different airbags or combinations of airbags may inflate in the car.

Do not obstruct airbags

Normally, airbags are hidden from the eye; many are literally sewn in beneath the interior upholstery and parts of the interior. These parts are designed in such a way that they can be quickly ruptured by an inflating bag. The intensity with which the airbag inflates is staggering. “You have to remember that airbags are part of the restraint system and only work properly in combination with seat belts. Airbags can be dangerous for an unrestrained passenger,” warns Petro Korop from Škoda Technical Development.

For airbags to work properly in an accident, the occupants must therefore be restrained. Similarly, it’s important to familiarise yourself with the car’s owner’s manual and find out where the airbag deploys. You should never place any objects on them, as they can turn into dangerous projectiles when the bag is deployed. A mobile phone left on the dashboard in front of the passenger is a bad idea, as is one particular passenger vice, especially in summer: feet on the dashboard. For the same reason, the airbag in front of the passenger seat must be deactivated if there is a rear-facing child seat.

Airbag Development

While the materials, the ways in which airbags are stitched, how many parts they’re made of and how they’re assembled and stored in the car are of course evolving, the principle of how they work has been fairly constant for a long time. The advent of electric cars has not fundamentally changed this, although engineers have had to adapt airbags to certain specifics.

“The positioning of the battery means that there is less deformation of the floor in a side-on collision, the movements of passengers or dummies are faster, and the head, side or central airbags have to be more robust. In general, though, it is precisely because of these deformation details that airbags and their functionality are tuned to each model, so electric cars don’t pose an additional challenge in this respect,” says Ševčíková. But the challenge in the future, she says, will be autonomous cars. These will allow passengers to occupy positions different from the usual ones today. And this will place new demands on restraint systems.