Airbags............. Truth or Myth
There are existing concerns in the emergency services community with regards to supplemental restraint systems and automatic roll-bars. It has been documented that there have been incidents where rescue workers have been injured from airbag deployments. However this should not stop or delay patient care at an accident scene. By following proper procedures, the risk of injury to your patients and rescue personal will be greatly reduced. Since the use of supplemental restraint systems, traffic deaths have been reduced drastically. There have been 2.6 million airbags deployed from late the 1980s to Sept. 1, 1998:
Air Bag Effectiveness (frontal crashes)
Car drivers: 31 percent fatality reduction
Car Passengers: 27 percent fatality reduction
Light truck drivers: 27 percent fatality reduction
Light truck passenger airbag, not enough data available at this time
It should be noted that airbags have also caused deaths, however many deaths are caused by not following recommended usage by the occupants of the vehicle. The following are statistics based on available data collected by the NHTSA:
Confirmed Air Bag Deaths (as of 9/1/98)
Children in rear-facing child safety seats: 15
Children not in rear-facing child safety seats: 51 (three restrained, but not properly)
Adult drivers: 42 (11properly restrained)
Adult passengers: 5 (two restrained)
Note: Proximity to the air bag has been the leading factor in nearly every death. The greatest issue involving deaths related to airbag deployment was improper use of seatbelts and infants riding in the front passenger seat.
The Airbag System and Deployment Sequence The driver's airbag unit consists of an airbag, and a gas generator. The unit is mounted in the steering wheel hub, concealed beneath a fabric covering. Identification can usually made by the visual telltale bulky appearance, embossed seams and letters such as SRS or Airbag embossed on the covering. Normally not visible, the gas generator will be mounted behind the airbag. The generator is a metal canister filled with sodium azide (solid rocket propellant). When a car is involved in a crash severe enough to activate the sensing unit(s), an electrical charge is routed to the gas generator which ignites the fuel. The fuel then creates a tremendous amount of inert gas filling the airbag. The total elapsed time from contact to full deployment of the airbag will vary, but should deploy within 0.03 seconds. At this time, vehicles equipped with pretensioners will also take up the slack in the seat belt system. This will prevent the passengers from having full contact with the deployed airbag. The pretensioners will not deploy from a side impact, or during a roll over situation.
The front passenger airbag may ignite at the same time as the driver side airbag. The new SMART airbags will analyze the weight/pressure applied on the passenger seat. In the case of a passenger under forty pounds (such as a child) the airbag may not deploy. Smart airbag sensors in the seat will signal the airbag controller when the required pressure is applied and arm the airbag for deployment.
Side impact restraint devices maybe mechanically activated by a sensor mounted in the door, outward side of a seat or near the B-pillar/rocker channel area. These devices can not be deactivated in the field! A pyrotechnic charge will initiate the sequence and ignite a sodium azide gas generator. Side impact airbags are located in either the door at arm rest level or within the outward side of the driver and passenger seats. The new side Impact Curtains (IC) will be located in the interior roof side rail. Once deployed, the curtain will inflate the entire length of the roof rail and extend downward to protect the occupants for injury caused by a side impact and glass fragments. Sausage type airbags (HPS) are deployed in a similar fashion, and can be seen on the tittle page.
Incidents With A Deployed Air Bag
Deployed air bags are not dangerous, however it should be noted that not all air bags will deploy during a crash. Side impact airbags are independent of the frontal bags. To decrease the chance of injury to improperly seated infants and children, some newer SMART air bags will detect if there is a passenger sitting in a seat. A child under forty pounds sitting in the front passenger seat may not arm this type of SRS. In this situation, the air bag may not deploy during a crash. But, if the electrical supply is not deactivated, a rescuer's own weight may now arm the air bag. This could possibly cause deployment if the proper precautions are not followed. Don't assume that seeing a deployed air bag will eliminate the chance of further air bag deployment. Treat any non-deployed air bag as if it were armed and could deploy, this will reduce the chance of an injury.
Practice the "5-10-20 Rule", keep a safe distance between you, the patient and that of the undeployed airbag.
Side impact curtain/air bags, maintain a safe distance of 5 inches or more
Driver side frontal air bags, maintain a safe distance of 10 inches or more
Passenger side frontal air bag, maintain a safe distance of 20 inches or more
Do not place any hard board/device between an airbag and a patient/rescuer
The air bag will not be hot, but escaping gases and the gas generator will be very hot. Burns can be expected should an unprotected hand come in contact with the canister behind the bag. Temperatures of 2,100 degrees are reached as the sodium azide within the canister completes the combustion (deflagration) process. Smoke is vented into the interior of the car which is a mixture of the by product of combustion and a powder (lubricant). Talcum powder or corn starch are used as lubricants. This will keep the airbag from sticking together while it's stored in the steering wheel hub, instrument panel/dashboard, or seat side panel.
Deployed Airbag Points to Remember:
Incident With An Undeployed Air Bag
Undeployed air bags can suddenly deploy during rescue operations releasing a tremendous amount of energy. This can be dangerous to both the patients and rescue personnel. Should circumstances permit, deactivate the battery as soon as possible. This will drain down the capacitor which stores an electrical charge used to ignite the gas generator. It is important to remember that each model vehicle may have an air bag with a different deactivation times even if the same manufacturer. Treat all non-deployed airbags as if they were active! Side impact bags maybe mechanically activated, independent of an electrical source.
Scanning the Vehicle
Scanning the vehicle is now a vital part of vehicle extrication, airbags and automatic roll-bars will now dictate how we provide patient care and the actual techniques of extrication. Scan and note all telltale hazards, adjust your procedure according to prescribed standards. Scanning should be a continuous process noting telltale signs of risk, stop a procedure if safety is below an expectable level and adjust accordingly. Some areas that you will need to automatically scan at an accident scene:
Exterior Scanning of the Vehicle
Environment, wires down, hazardous materials, unstable position of vehicle or fuel leaks
Stabilization; loaded bumpers, attachment and placement points for stability
Glass type, is it intrusion resistant, which window will make easy access
Doors, which doors are unlocked, can the doors be opened, remember "Try before we Pry"
Are there icons, placards or other signs of air bags or automatic roll bars
Check the crumple zone, is there substantial damage from the crash force to create internal injuries that might be overlooked
Interior Scanning of the Vehicle
Check the steering wheel for signs of air bags and deformity
Look for icons or placards at the visor, dash, posts/pillars, interior roof side rail, window glass, vehicle identification number (VIN), side or back of seats, and the steering wheel hub.
Convertibles, look for automatic roll-bars, dual pop-up or flip-up type bars
Check for mechanism of injury, deaths have occurred do to internal injuries after treating and releasing patients. Note if the steering wheel deformed.
Automatic Roll-bars (ROPS)
Mercedes Convertible with automatic dual pop-up rollbars (deployed) Photos by Ron ShawVolvo and BMW are using the automatic pop-up roll-bar systems in their 1999 production model convertibles. Mercedes has been using both dual pop-up and flip-up roll-bar systems on selected convertibles for many years. The Mercedes units are hydraulic while the BMW and Volvo are mechanical. They are deceiving in looks, and can easily be mistaken for a head rest or as part of the trim to the soft top of the convertible.
Volvo pop-up style ROPS (active) Photo by Ron Shaw
To further prevent injury to rescue personal/patients, do not risk placing hard objects such as a short/long board or allow personnel over or in the path of any undeployed roll bar system. Deployment will take place when the automatic roll-bar sensor detects wheels are off the ground/ surface. The roll-bar system is also interconnected with the airbag system and may deploy when the airbags are activated. Some systems can manually deploy the roll bar by the operator with a dash mounted switch. If feasible, rescue personal should attempt to safely activate the operator's manual activation switch to manually deploy the system in a controlled sequence. This will prevent injury to patients and personal from an unsuspected accidental deployment. Vehicle extrication preplanning at a local dealership will greatly assist company officers.
Injuries, Look Beyond the Obvious --- Check the S.C.E.N.E.
Prior to the introduction of air bags and lap-shoulder belts, seriously injured occupants involved in crashes usually had visible injuries (such as bleeding, facial lacerations, abrasions, bruises, and broken facial bones) that were obvious to rescue personnel. Now, occupants protected by these devices do not have as many of the previously visible injuries, but still may need medical attention for internal injuries. In a crash serious internal injuries may be present, but may not be externally apparent. To address this situation and increase the chances that crash victims receive timely and appropriate emergency care, look beyond the obvious. First responders can greatly assist medical personnel by gathering information about the mechanism of injury. The following information should be collected and reported to alert medical personnel for possible internal injuries:
Remember these important points by using S.C.E.N.E.
In Conclusion Remember These Important Points
It is important to preplan for an accident just as you would for any other emergency service incident. Department members should be familiar with new car construction and identifying hazards to rescuers. Start locally by visiting your local auto dealer. Ask about new vehicle construction, safety features, battery locations, request handouts and Emergency Response Guidelines for Rescues.
Questions frequently asked By Emergency Personnel
How does an air bag work?
When a frontal, near-frontal, side-impact crash occurs at speeds comparable to a 10 to 14 mile per hour during a frontal crash into a solid object, vehicle crash sensors trigger a chemical reaction inside the air bag module, and this causes the air bag (which is folded and packed like a parachute inside the steering wheel, dashboard, or seat side panel) to inflate. The rapidly inflating bag splits open the cover on the steering wheel, dashboard, seat or side panel, and fully inflates to help protect the driver and passenger(s). This entire inflation sequence takes place in less than 1/10 of a second. Less than one second after inflation, the air bag begins to deflate automatically.
2. How do I know if a vehicle has an air bag?
If an air bag has deployed, you will see it drooping from the steering wheel, the dashboard, or the side of the driver's and passenger's seat. If there is no visible air bag, look for the words, Supplemental Inflatable Restraint, Air Bag, or the initials, SIR, SRS, SIPS, HPS, IC (Volvo/Mercedes impact curtain) printed on the steering wheel hub, instrument panel, dashboard, windshield, driver's side B-post/pillar, interior roof rail, or on the side or back of the seat when the car is equipped with side air bags. If you still can't tell whether the vehicle has an air bag or not, you should assume it has one, especially if the vehicle is a newer model.
3. Is a deployed air bag dangerous?
Once a bag has been deployed it will not re-deploy. Many people think that a recently deployed air bag is about to catch fire because they see "smoke". This is the byproduct of combustion from the sodium azide and a powdery substance (talcum powder or corn starch) that is used to keep the air bag from sticking together while it is packed away in the steering wheel hub, dashboard, or side seat/door panel. When the air bag inflates, this powder can vent into the passengers' compartment, and the airborne particles may be deposited as a powdery dust on and around the bag. This powdery dust may contain small amounts of residue from the chemical reaction that can cause minor irritation to the eyes and skin. The residue will not usually be an issue, however persons with severe allergies may have a reaction. Rescuers should wear proper PPE, gloves and eye protection that is normally worn to protect themselves from sharp edges, glass, or bodily fluids will also protect them from this powdery residue. Do not cut open the airbag, this will expose the gas generator which will be extremely hot.
4. Is it safe to breathe the passenger compartment air after an air bag has deployed?
There have been no cases of acute or long-lasting respiratory distress reported by rescue workers attending to crash victims who were exposed to air bag deployment by-products. There have been a few complaints of minor distress, such as brief coughing spells. However, simulated tests were conducted with volunteers - chronic asthmatics - who were subjected to long-term exposure (20 minutes) to the atmosphere inside a vehicle with the windows rolled up, after the driver and passenger-side air bags had deployed. In this type of environment, test results revealed that prolonged exposure to this atmosphere can cause significant asthmatic reactions in some people. Therefore, if a crash victim appears to be suffering from acute respiratory distress, rescue workers should consider the possibility of an asthmatic attack, and treat the victim accordingly.
5. Do undeployed air bags pose a danger to rescue personnel and victims?
Although it's rare, there have been cases were air bags have deploy during rescue operations and created a hazardous operating condition. This can result in injury to rescue personnel and cause and delay medical assistance to occupants. Use proper procedures as outline in this guideline to further reduce the possibility of injury.
6. Why deactivate the vehicle's electrical system?
Deactivating the vehicle's electrical system will reduce the risk of deployment to all electrically initiated air bags after a specific deactivation time. There may be dual batteries as in diesel vehicles where it will be necessary to seek and disconnect both batteries. Some alarm systems may also back feed the system and supply energy to the igniters. Do not assume that the airbags will not deploy even after disconnecting the battery. There may be other systems such as GPS or a cell phone that could potentially back feed the system to supply an ignition source. Static electricity can also set off an airbag, use the 5-10-20 inch distance rule around airbags. Five inches from any side impact back, ten inches from any driver's side frontal and twenty inches from the passenger's side frontal. It is also important not to place any hard objects such as a back board between the airbag and patient/rescuers. The force from the deployment of a air bag will be transmitted through the hard board device to the rescuer or the patient.
7. How does one deactivate mechanically operated side or frontal air bags?
You can not deactivate most mechanical sensors in the field, this should be left to properly trained technicians. The best safety precaution is to deactivate all electrical sources.
8. What if there is a fire at the scene?
In case of a severe fire, the gas generators, after several minutes may reach 350 degrees and ignite, causing the air bag to deploy. Extreme care should be taken around frontal airbags, there have been documented cases of a failure to the air bag system during a fire situation. Shrapnel and entire air bag assemblies have released and propelled beyond the vehicle. The sodium azide is water reactive, this means that moisture will react with the sodium azide and cause a violent reaction. Do not cut or pry near the steering wheel column/hub of an undeployed airbag. This could expose the chemical cartridge which is water reactive. The use of any effective fire fighting medium, including water can be used to extinguish airbag vehicle fires. Use proper fire extinguishing and rescue procedures. Remember that there have been cases of failures to the airbag assembly during a fire situation. Approach the vehicle and fight the fire according to recommended standards , cool the area around the airbag module as soon as possible.