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Environmental Effects on Airbag Components

The importance of thorough environmental testing came up once again in the news last week. Takata’s most recent recall will tack on 35 million more airbags, bringing the number to at least 63 million in the United States alone.

Federal safety regulators said the cause of the defect is long-term exposure to changing moisture and temperature conditions. The culprit of the airbag defect is a compound called ammonium nitrate. Over time, when exposed to variations in high air temperature and moisture fluctuations, ammonium nitrate can become unstable, acting as a propellant. When this happens, the airbag inflates without warning and shoots out metal fragments toward the driver and passenger. This can cause accidents, great bodily harm, and, in some cases, death.

Airbags Deploy. Image from WikiMedia When an airbag inflates, it's basically a direct and forced chemical reaction. Different chemical mixtures are used to accomplish this, the mixture can react differently in various environments. Image from WikiMedia.

An airbag has several components: steering wheel and airbag cover, inflator, contact unit, sensor system, and control and diagnostic systems. Inside the airbag is a small tray that contains a solid chemical mixture that is used to deploy the airbag in a direct and controlled chemical reaction. Chemical combinations used in airbags have changed over time and can vary from manufacturer to manufacturer. When a collision is detected and an electric charge ignites the mixture that deploys the airbag.

A car detects a collision through a few different mechanisms. It uses algorithms, vehicle deceleration data and calibrated parameters from test crash events, accelerometers, and door-pressure sensors. The airbag has milliseconds to inflate between the exact moment of a collision and bodily impact of a driver or passenger hitting the steering wheel or instrument panel occurs.

Ambient environments wherever the product will be used need to be considered when environmentally testing products for consumer use. This particular defect is prevalent in the Southeastern United States where it is often hot and humid. Temperature and moisture levels in this region can fluctuate significantly during the day and seasonally.

Thoroughly testing products and their components for every environment they may encounter prior to market release is essential. Testing with an electrodynamic shaker can help determine if a car hit a pothole or another object that can justify the deploying of an airbag. Using a humidity chamber, both temperature and humidity tests can be done to ensure product quality and robustness. Environmental testing can help find product design and production flaws prior to market introduction. Doing so reduces the amount of time, money, and other resources spent on recalls and warranty issues.

Do you have questions about testing specifications? Consult with our environmental testing experts on how you can improve product quality through a temperature and humidity chamber or electrodynamic vibration testing program.