How Do Car Airbags Work?

[DelBennett]

Airbag Working Principle: When a frontal collision occurs, the airbag control system detects an impact force (deceleration) exceeding the preset threshold. The airbag computer immediately activates the electrical circuit of the inflator's squib, igniting the firing medium inside. The flame then ignites the propellant and gas generant, producing a large volume of gas that inflates the airbag within 0.03 seconds. The rapidly expanding airbag bursts through the steering wheel cover, deploying toward the driver and passengers, cushioning their heads and chests against the inflated airbag to absorb impact forces. Subsequently, the gas is vented from the airbag. Typical airbag systems consist of two main components: the crash detection and ignition device (or sensor) and the gas generator-equipped airbag (or cushion). Upon sensor activation, the control circuit evaluates collision signals. The airbag deploys only if simultaneous signals are received from two sensors. Since car generators and batteries are often located in vulnerable front areas, airbag control systems feature backup power to ensure functionality. After confirming deployment conditions, the control circuit sends current to the igniter, causing rapid heating that triggers sodium azide propellant combustion. This near-explosive chemical reaction generates harmless nitrogen-rich gas, inflating the airbag fully. The forceful expansion breaks through the steering wheel cover, protecting the driver's head. During ignition, the igniter assembly's metal mesh cools the rapidly expanding gas, while designed vents allow gradual deflation for controlled deceleration and post-collision visibility maintenance. The Supplemental Restraint System (SRS) includes sensor assemblies, inflators, folded airbags, igniters, solid-state nitrogen, warning lights, etc. Airbags are designed to inflate before secondary occupant impact during collisions. As complementary devices to seatbelt restraint systems, they form the SRS. The system integrates airbag modules (combining cushions and inflators), crash sensors that trigger deployment, and wiring harnesses transmitting sensor signals. Airbag Usage Notes: Mandatory Seatbelt Use: Beyond providing primary protection, seatbelts control occupant deceleration during early collision phases, ensuring optimal timing and positioning for airbag contact to minimize deployment force. Unbelted occupants experience minimal initial restraint, leading to premature contact with partially inflated airbags—their high expansion speed and uneven pressure may cause injury. Clear Deployment Zone: Airbags deploy with tremendous force (250-350 km/h initial speed, 150-200 kg impact force). Objects placed near airbags may become dangerous projectiles, causing secondary injuries. Never place items in front of or near airbags. Avoid Impacts and Modifications: Prevent forceful impacts that could trigger accidental deployment. Modifications affecting SRS wiring may disable airbags. Seat covers may also impair side airbag deployment. Seat Positioning: The driver airbag's danger zone spans 5-8 cm from the inflator. Maintaining 25 cm from the steering wheel center (accounting for 320 km/h inflation speed) ensures safety. Incorrect seating postures during crashes may cause severe injuries. Child Passenger Warning: While optimal for adults, SRS and three-point seatbelts can be hazardous for children. Crash forces may cause chest fractures, and deploying airbags pose suffocation risks. Airbag Lifespan: Due to manufacturer confidentiality and lack of standardization, many assume airbag lifespan matches vehicle longevity. However, airbag reliability typically declines after 8-10 years. Regular maintenance every 10,000-20,000 km is advised. Persistent airbag warning lights after 6-8 seconds of engine start indicate immediate dealership inspection is required.

[DiAmelia]

I've always considered airbags to be a crucial element in automotive safety, as they protect us during collisions. Here's how they work: vehicles are equipped with acceleration sensors that detect sudden deceleration (like in a crash) and send signals to the control unit, which then triggers a small explosive charge or gas generator. This device rapidly produces a large volume of nitrogen gas, inflating the nylon airbag within milliseconds, creating a cushion-like barrier in front of you to absorb impact forces and prevent you from hitting the steering wheel or windshield. It's important to avoid placing objects near the airbag deployment area on the dashboard, as this could interfere with its operation. During regular maintenance, have a technician check the sensors and wiring, since this system has saved countless lives. Imagine a high-speed accident where the airbag deploys instantly alongside seat belts, potentially reducing injuries by half. I've also heard modern vehicles come with side airbags and curtain airbags, though their core operating principle remains the same.