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What you need to know about AIRBAGS?

If you are among the millions of Americans who will soon purchase, lease or rent a car, chances are it will be equipped with a supplemental restraint system, commonly known as an airbag. Airbags are called supplemental restraints because they are designed to work in combination with safety belts. You should always wear your safety belt regardless of whether or not your car has an airbag. Most new passenger cars (and many light trucks and vans) are equipped with driver side airbags. Many cars also have airbags for front seat passengers. Virtually all new cars, light trucks and vans will have driver and passenger side airbags by 1998, most of them sooner.

The Airbag System
The airbag system consists of three basic components an airbag module, crash sensors, and a diagnostic unit.

1. The AIRBAG MODULE contains both an inflate unit and the lightweight fabric airbag. The driver side module is located in the steering wheel hub, and the passenger side module is located in the instrument panel. When fully inflated, the driver side airbag is approximately the size of a large beach ball. The passenger side airbag is necessarily two to three times larger since the distance between the right front passenger and the instrument panel is much greater than the distance between the driver and the steering wheel.

2. The CRASH SENSORS are located either in the front of the vehicle or in the passenger compartment. Vehicles can have between one and five crash sensors. The sensors are switches that are only activated by forces typically generated in significant frontal or near frontal crashes. Sensors measure deceleration, the rate at which the vehicle slows down. Because of this, the vehicle speed at which the sensors activate the airbag varies with the nature of the collision. Airbags will not activate during sudden braking, while driving on rough or uneven pavement, or by hitting the bumper with a hammer. In fact, the maximum force generated in the severest braking is only about 1/10th of that necessary to activate the airbag system.
3. The DIAGNOSTIC UNIT is an electronic device which monitors the airbag system. The unit is activated when the vehicle's ignition is turned on. If the unit identifies a problem, a warning light alerts the driver to take the vehicle to an authorized service department for examination of the airbag system. Most diagnostic units contain a capacitor which stores enough electrical energy to deploy the airbag in the event that the vehicle's battery is destroyed very early in a crash sequence.
When Do Airbags Deploy?

Airbags are designed to deploy in frontal and near frontal collisions which are comparable to hitting a solid barrier at approximately 10 to 14 miles per hour (mph). Roughly speaking, a 14 mph barrier collision is equivalent to striking a parked car of similar size across the full front of each vehicle at about 28 mph. This is because the parked car absorbs some of the energy of the crash, thus slowing the deceleration of the striking vehicle. Unlike crash tests into barriers, real world crashes typically occur at angles and the crash forces usually are not evenly distributed across the front of the vehicle. Consequently, the vehicle speed required to deploy the airbags in a real world crash can be much higher.

Because airbags sensors measure deceleration, vehicle speed and damage are not good indicators of whether or not an airbags should have deployed. Occasionally, a crash results from the vehicle's undercarriage striking a low object protruding above the roadway surface. Despite the lack of visible front end damage, high deceleration forces may occur in this type of crash, resulting in the deployment of the airbags

Most airbags are designed to automatically deploy in the event of a vehicle fire when temperatures reach 300 to 400 degrees Fahrenheit. This safety feature helps to ensure that such temperatures do not cause an explosion of the inflate unit within the airbags module.

Airbags are not designed to deploy in side impact, rear or rollover crashes. Since airbags deploy only once and begin deflating immediately, they are not likely to be of benefit if a vehicle hits more than one object during the course of a collision. Safety belts help reduce the risk of injury in many types of crashes. Moreover, they help restrain occupants during the initial collision and any subsequent collision. Thus, safety belts should always be worn even in airbag equipped cars

When a Collision Occurs?

When a collision occurs, the vehicle rapidly decelerates while its structure absorbs the majority of the crash forces. Unbelted occupants continue to move forward at the vehicle's original speed until the car's interior (the steering wheel, instrument panel, windshield, etc.) stops their movement. Belted occupants come to a more gradual stop by being secured to the vehicle's structure. In severe crashes, even properly belted occupants may come in contact with the car's interior.

Airbags supplement the safety belt by reducing the likelihood that the occupant's head and upper torso will strike some part of the vehicle's interior. They also help reduce the risk of serious injury by distributing crash forces more evenly across the occupant's body.

When the sensors detect a moderate to severe frontal collision, they close an electrical circuit and send a signal to the inflate unit within the airbag module. An ignite starts a chemical reaction which produces harmless nitrogen gas. The nitrogen gas passes through filters and fills the airbag which then bursts through the module cover. Some passenger side airbags use argon gas stored in a high pressure canister rather than chemically generated gas. The argon gas which fills the airbag is also harmless.

From the onset of the collision, the entire deployment and inflation process takes only about 1/20th of a second, faster than the blink of an eye. Airbags must inflate this rapidly if they are to help reduce the risk of the occupant hitting the vehicle's interior components.

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