VEHICLE AIR BAGS: JUST THE FACTS
Since September 1989, all new cars sold in the United States have been required to have an automatic crash protection system as standard equipment. While automatic safety belts fulfill this requirement, many manufacturers are installing automatic air bags to provide crash protection for the driver and are beginning to offer them for the right front-seat passenger.
Air bags can prevent major injuries and reduce the death toll resulting from head-on collisions. However, due to their inherent qualities, they present new problems to both the victims and the emergency responders who encoun- ers who encounter deflated air bags or air bags that are present but not deployed.
HOW AIR BAGS WORK
A head-on or near head-on impact of approximately 12 to 15 miles per hour is necessary to activate the sensors that electrically trigger the inflator. Impact from the side, the rear, or a rollover will not activate the sensors, which are located in the front of the car. The inflator activates the igniter, starting a chemical chain reaction between solid sodium azide, molybdenum disulfide, and sulfur inside a canister at the top of the steering column. This reaction creates a large amount of nitrogen gas, heat, and a small quantity of sodium oxide. These are released into the bag, which bursts through the plastic cover on the center of the steering wheel hub. From initial electrical contact to air bag inflation takes only 6 milliseconds (0.006 seconds). Full deployment of the bag takes only 25 more milliseconds, and deflation through vent holes in the bag starts as soon as it is tully inflated (less than 1/20 of a second).
In fact, deployment happens so fast that the bag actually appears to begin deflating before reaching maximum inflation. Due to the vent holes it is virtually impossible for the bag to remain inflated long enough for the victim to develop a breathing problem.
VICTIM INJURIES
Recently air bags have come under fire as some reports of injuries have been documented. These injuries consist of minor bums to the fingers and abrasions to the faces and necks of the driver-victims of front-end collisions.
Randall Edwards, manager of safety programs for Chrysler Corporation, the first U. S. automaker to install air bags in cars, confirms that there have been some minor injuries associated with the deployment of the bags in Chrysler cars. He describes them as first-degree and some second-degree burns to the fingers of drivers who hold their hands in the 3 and 9 o’clock positions on the steering wheel. Since the vent holes to release the hot gases from the bag are located in the same positions, gas comes in contact with the driver’s fingers and causes the burns. Chrysler is redesigning the bags to place the vent holes in the 12 o’clock position and away from most drivers’ fingers. Other car manufacturers do not report the same problem because their bags vent slower. Edwards describes the brush burns to the face as resembling a skinned knee from a fall on a basketball court. Both types of injuries are very minor and usually clear up in a matter of days, he adds. While they are painful for a short period of time, they certainly are a very minor consequence when involved in a head-on accident.
DANGERS TO RESCUERS
There are many misleading rumors currently circulating concerning the dangers air bag-equipped cars pose to rescuers.
Rumor #1; The powdery residue found on the air bags after deployment is toxic to victims and rescuers. This is FALSE. The residue that could possibly be emitted from the vent holes during deployment is sodium hydroxide, a potential skin irritant. This residue eventually reacts with carbon dioxide in the air to form sodium carbonate and sodium bicarbonate (baking soda). Contact with an open wound or the eyes may produce slight irritation. It is nontoxic but obviously should be washed or brushed off the patient and/or rescuer just as you would any other substance. The powdery residue on the outside of the air bag is cornstarch and is used to lubricate the bag for easier deployment. Cornstarch is obviously nontoxic.
Rumor #2: The sodium azide, in the canister where the chemical reaction producing the nitrogen gas takes place, is harmful. MAYBE. Sodium azide may be toxic if ingested in large doses. There is no way for the vehicle’s occupants or rescuers to ingest the sodium azide—it is in a sealed container located where they normally could not contact it. As to the toxicity of sodium azide, it has been used in the treatment of high blood pressure. The U.S. Department of Transportation states that sodium azide is “not as toxic as some substances found in common household materials.”
Rumor #3: The fumes from the chemical reaction of the sodium azide, molybdenum disulfide, and sulfur are toxic, and rescuers should wait at least 20 minutes before approaching the vehicle to allow the fumes to dissipate. This is FALSE. The fumes may cause a very slight throat irritation to the occupants of the accident vehicle. Tests conducted on severely asthmatic volunteers resulted in only a small number of them suffering a slightly irritating cough for a day or two. The vast majority exhibited no aftereffects whatsoever. The volume of the fumes is extremely small and will be completely dissipated by the time rescuers arrive.
Rumor #4: All parts of the steering wheel and steering column are extremely hot, and rescuers should avoid them. This is PARTIALLY TRUE. The chemical reaction happens so fast that heat is generated. The steering column will get hot (approximately 300°F) but will cool off by the time rescuers arrive on the scene.
Rumor #5: If rescuers arrive on the scene of an accident involving an air bag-equipped car and the bag has not deployed, they cannot attempt to stabilize the vehicle for fear that any jarring may cause the bag to deploy. FALSE. In most air bag-equipped vehicles, two sensors located near the radiator must be activated simultaneously in order to trigger deployment. This would be almost impossible to do accidently during a stabilizing operation.
RESPONSE
When responding to an accident where an automobile’s air bag has been deployed, always wear gloves and eye protection and remove your gloves and wash your hands after exposure to the dust. Brush the dusty residue off the victim and proceed with normal rescue operations. Deployed air bags are not dangerous.
A vehicle equipped with an air bag that did not deploy will have a rectangular and unusually large (about 6″ x 9″) steering wheel hub covered with a scored, soft plastic material with “Supplemental Inflatable Restraint,” “Air Bag,” “S.I.R.,” or “SRS” embossed on the surface. You must take the following precautions at an accident involving such a vehicle:
To prevent accidental deployment during rescue operations (which is very unlikely), cut or remove the negative battery cable. If there is some doubt as to which cable is negative, disconnect both cables. Even after this step, due to an energy reserve system in many new cars that lasts from 1 second to 20 minutes (up to 30 minutes in Rolls Royces and Bentleys), there is a remote possibility that the air bag still could inflate. While assisting the victim(s), do not place your body or tools near the air bag module for 20 minutes after cutting the cable(s) except for essential maneuvers.
With mechanically activated systems, currently found only in 1990 Jaguar coupes and convertibles, take extreme care to avoid sharp impacts to the steering column, particularly in the forward or rearward directions. Cutting the steering wheel rim is permissible if these types of impacts can be avoided.
- Never cut or drill into the steering wheel hub (which contains the air bag module), as you might rupture the sodium azide canister.
- Never use a cutting torch or other heat-producing device on the steering wheel or column. The excessive heat could cause the air bag to self-deploy.
- If damaged cars with nondeployed air bags are to be used for training exercises, contact the local auto dealer for instructions on how to deploy the bag safely prior to beginning the
- exercise to avoid problems later.
- If the canister of sodium azidebased propellant is ruptured, do not touch or ingest any of the unburned substance, which will be found in tablet form.
As with any vehicle fire, firefighters responding to a fire in a car equipped with an air bag should wear full turnout gear, including SCBA, to protect against both the potentially dangerous by-products of air bag activation
and the fire itself. Any effective medium, including water, may be used to fight the fire. During firefighting operations the heat may activate an undeployed air bag. While deployment will be normal (no explosions), keep away from the steering wheel hub to avoid injury.
Armed with the facts concerning automobile air bags and exercising caution, rescuers can continue to provide care and assistance to the victims of motor vehicle accidents—and they can do it safely.