In this blog post, we’ll take an in-depth look at airbags—a core component of automotive safety technology—including their origins, how they work, the various types available, and their actual safety performance.

Why Were Airbags Developed?

Since the publication of Ralph Nader’s book ‘Unsafe at Any Speed’ over 40 years ago, car dashboards, steering wheels, and other components have been continuously improved to enhance occupant safety. Among these advancements in safety technology, the emergence of airbags is particularly noteworthy. Although they are usually inconspicuous to drivers and passengers, airbags—which remain quietly in place, ready for that single moment of an accident—have become a quintessential symbol of automotive safety today. In this article, we will examine, in order, how airbags came to be, how they work, and what types exist.
In 1965, American civil rights activist Ralph Nader published ‘Not Safe at Any Speed’, a book criticizing automakers’ indifference to safety. This book served as a catalyst for raising widespread public awareness of the structural defects and safety issues in cars at the time, and it had a significant impact on the subsequent strengthening of automotive safety standards and the widespread adoption of seat belts and airbags.
The history of airbags dates back to the 1950s. At the time, John Hetrick, who was working as a torpedo development engineer for the U.S. Navy, was involved in a sudden accident while driving with his family. Since vehicles at the time had almost no safety features to protect occupants, he instinctively reached out with his arms to shield his family. Inspired by this experience, he began to contemplate a device that could protect occupants at the moment of impact, and he conceived of a mechanism that would use compressed air to instantly inflate an airbag. Ultimately, in 1952, he filed a patent for the concept of an airbag—a device that rapidly inflates an airbag during a car crash to protect occupants.
Airbags are a prime example of passive safety devices that control the movement of occupants during a collision, thereby reducing direct contact between their bodies and the vehicle’s interior structure. The core principle of airbags lies in reducing impact force. In physics, impact force is expressed as impulse divided by the duration of the collision. In the event of an accident, while the total impulse experienced by the occupant does not change significantly, extending the duration of the collision—even slightly—can reduce the impact force transmitted to the body in an instant. Airbags utilize precisely this principle. They inflate rapidly upon impact, extending the time it takes for occupants to collide with the vehicle’s interior, thereby effectively reducing the impact transmitted to the head, chest, and other areas.

How do airbags work?

The airbag deployment process is broadly divided into three stages: detection, processing, and inflation. First, collision sensors installed throughout the vehicle detect the sudden deceleration caused by an accident. Next, an electronic control unit called the SDM (Sensing and Diagnostic Module) analyzes the information transmitted from the sensors to determine whether an actual collision has occurred and whether the impact is severe enough to deploy the airbags. If the collision intensity exceeds a preset threshold, the control unit sends an ignition signal to the gas generator, and in response to this signal, the airbag inflates instantly within tens of milliseconds.
Early airbags used sodium azide (NaN₃) to generate nitrogen gas. First, when sodium azide is exposed to high heat inside the gas generator, it decomposes into nitrogen gas (N₂) and metallic sodium (Na). The nitrogen gas produced at this time rapidly fills the airbag, causing it to fully inflate in about 0.03 to 0.05 seconds.
However, the metallic sodium produced during this process is a highly reactive substance and can be dangerous if left unchecked. To address this, a second chemical reaction takes place. The sodium metal reacts with potassium nitrate (KNO₃) to form sodium oxide (Na₂O) and potassium oxide (K₂O). In other words, this process converts the highly reactive metal into relatively stable oxides.
In the final stage, the sodium oxide and potassium oxide react again with silicon dioxide (SiO₂) to form silicates. Since silicates are stable substances well known as the main components of glass and rock, the initially hazardous byproducts are ultimately transformed into substances that are relatively safe for humans.
In summary, the gas generator in an airbag undergoes three stages of chemical reactions. In the first stage, nitrogen gas is produced to inflate the airbag; in the second stage, the hazardous metallic sodium generated is converted into oxides; and in the final stage, these oxides are converted into stable silicates to enhance safety. In other words, an airbag is not simply a device that inflates with air, but a sophisticated safety device that triggers a series of chemical reactions in a very short period of time to protect the lives of occupants.
However, most cars currently in production use gas generators such as guanidine nitrate—which offer improved safety and environmental performance—instead of sodium azide. Therefore, the reaction process described above can be viewed as an example to help understand the typical operating principle of early-generation airbags.

What types of airbags are there?

Airbags are classified into various types based on their installation location and the occupants they protect. The most common type is the front airbag, installed in front of the driver’s and front passenger’s seats. In the event of a frontal collision, it prevents the driver’s and front passenger’s heads and chests from striking the steering wheel or dashboard directly. Today, it is a standard safety feature in most passenger cars.
Side airbags, designed to protect against both frontal and side collisions, are also widely used. Installed in the vehicle’s doors or along the sides of the seats, side airbags rapidly inflate upon impact to reduce the force transmitted to the chest and pelvic areas of the driver and passengers. Since side collisions often result in severe injuries due to limited space to absorb the impact, side airbags play a crucial role.
Recently, curtain airbags, which protect the head, have also become commonplace. Curtain airbags are installed along the sides of the vehicle’s roof and deploy like a curtain along the windows in the event of a crash. This prevents the head from colliding directly with the window or the vehicle body and also protects occupants in rollover accidents.
In addition, various types of airbags have been developed and are now in use, including knee airbags to reduce knee injuries, torso airbags to enhance torso protection, and center airbags to prevent front-seat occupants from colliding with one another. Recently, airbag technology has evolved even further, with pedestrian airbags—designed to reduce head impact on pedestrians in the event of a collision—being installed in some vehicles.

Can airbags really save lives?

So, can airbags actually save lives at the moment of a crash? To put it simply, yes. However, airbags are not a substitute for seat belts; they are most effective when used in conjunction with seat belts.
In the event of a collision, seat belts secure the occupant to the seat, reducing the movement of the entire body, while airbags mitigate the impact transmitted to the head and chest. Since the two devices are designed to complement each other’s shortcomings, it is difficult to expect sufficient protection from either one alone.
In fact, according to research by the U.S. National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS), airbags have been shown to significantly reduce the risk of death for drivers and front-seat passengers in head-on collisions. Additionally, side airbags have also been confirmed to be effective in reducing head and chest injuries in side-impact collisions. Based on these findings, most countries now mandate airbag installation as part of their new vehicle safety standards and use it as a key criterion for evaluating vehicle safety.
However, airbags are not always safe. Because they inflate at extremely high speeds, they can actually cause injuries if the occupant is not wearing a seat belt or is not seated in the correct position. In particular, airbags can pose a serious risk when a young child is seated in the front passenger seat or when an infant car seat is installed in the front seat, so it is essential to strictly follow the manufacturer’s safety guidelines.

Constantly Evolving Automotive Safety Technology

So far, we have examined the development history of airbags—which began as small air pouches—their operating principles, the various types based on installation location, and their safety features. Airbags have evolved from their early, simple deployment mechanisms into “smart airbags” that comprehensively analyze factors such as the occupant’s weight, seating posture, seat belt usage, and collision intensity to determine whether to deploy and adjust the inflation force.
Recently, technologies that utilize cameras, radar, and various sensors installed in vehicles to assess collision situations with greater precision have also been advancing. As autonomous driving technology and vehicle safety technology continue to advance, airbags are expected to continue evolving to actively respond to a wide range of situations.
Although we are usually unaware of their existence, airbags are the devices that act the fastest to protect occupants’ lives in the split second of an accident. Quietly performing their role behind the scenes, airbags can truly be called the “lonely guardians” that represent today’s automotive safety technology.