Emergency Rescuer's Guide to Vehicles Fitted with Supplemental Restraint Systems (SRS)
(Airbags and Pyrotechnic Seat Belt Pretensioners)
Issue 6a—December 2007
Download PDF Version PDF: 74 KB
Issue 6—October 2006
Download PDF Version PDF: 53 KB
Compiled by the Department of Infrastructure, Transport, Regional Development and Local Government, Canberra.
Table of Contents
- How an airbag SRS works
- Airbag SRS chemicals
- How to identify a vehicle fitted with an airbag SRS
- How to de-activate an airbag SRS
- Vehicle fire
- Vehicle recovery—towing
- Rescue with deployed airbag SRS
- Rescue myths
- Why seatbelts may not have deployed
- Airbag SRS identification and de-activation list
This guide has been compiled from information supplied to the Department of Infrastructure, Transport, Regional Development and Local Government vehicle manufacturers and by the US Department of Transportation, National Highway Traffic Safety Administration (NHTSA). Information contained in this guide is current at the time of publication. Further advice and information may be sought from the Service Departments of the relevant vehicle manufacturers.
The Department of Infrastructure, Transport, Regional Development and Local Government would like to thank the Federal Chamber of Automotive Industries (FCAI) and all motor vehicle manufacturers for their assistance in producing these guidelines.
In the interests of promoting safe rescue operations, the Department of Transprt and Regional Services encourages the copying and dissemination
The Department of Infrastructure, Transport, Regional Development and Local Government has used due care and skill in the preparation of this guide, however as some information used in that preparation has been provided by other parties, the Commonwealth gives no warranty as to the accuracy, reliability, fitness for purpose or otherwise of the information contained in the guide.
This booklet is produced to assist Emergency Rescue Personnel by providing information about vehicles equipped with driver, passenger and side airbags and pyrotechnic seatbelt pretensioners as supplemental restraint systems.
This guide gives Emergency Rescue Personnel information to handle rescues involving a vehicle equipped with an airbag or seatbelt pretensioner SRS, whether or not it has deployed. Its aim is to relieve any unnecessary concern regarding rescues on vehicles fitted with these pyrotechnic devices.
The most important thing to remember is that occupants and rescuers are not exposed to harmful levels of chemicals with a deployed or undeployed airbag SRS. The gas generant, which contains either sodium azide or nitrocellulose is securely contained and sealed before deployment and is consumed during a deployment. Testing shows that there are no detectable levels of sodium azide in the combustion by-products.The by-products of nitrocellulose combustion are relatively harmless in the concentrations found during an Airbag SRS deployment.
An airbag SRS may be an electrical or mechanical type, with some or all of the following elements;
- The airbag SRS module—includes an inflator, an airbag, and a trim cover
- The electronic diagnostic module—monitors the airbag SRS electrical system for faults and disables the system when certain faults are detected
- Crash sensors—detect sudden deceleration. Internal sensors are integrated within the airbag SRS module, resulting in a self-contained system. External sensors are located elsewhere on the vehicle.
- A back-up power supply—provides power to the system in case the battery is damaged before the crash sensors operate.
The driver-side airbag SRS module is located in the hub of the steering wheel. The passenger-side airbag SRS module (if the vehicle is so equipped) is in the dashboard above the glove compartment. The side impact airbag SRS module (if the vehicle is so equipped) is in either the door panel or the seat and may not be visually identifiable.
The airbag SRS inflator contains a solid chemical gas generant consisting of;
- solid pellets or disks of sodium azide and an oxidiser, such as copper oxide or,
- a solid cylinder of nitrocellulose.
The solid chemicals are safely stored in a metal chamber inside the airbag SRS module. Each inflator is sealed to keep out moisture.
An airbag SRS is designed to deploy in moderate to major frontal crashes. The following four steps show how the airbag SRS works;
- In a frontal impact, sensor(s) in the vehicle detect the sudden deceleration. When the sensor(s) close, electricity flows to the inflator and causes ignition of the gas generant.
- The gas generant then rapidly burns in the metal chamber. The rapid burning produces inert gases and small amounts of dust. The inert gases and dust are cooled and filtered, during inflation of the airbag.
- The inflating airbag splits open the trim cover. The airbag then rapidly unfolds and inflates in front of the occupant.
NOTE: steps 1-3 take place in a fraction of a second.
- After inflation, the gas is vented through openings or open weave areas in the airbag. Airbags deflate at once and may be pushed aside for occupant removal.
NOTE: some recent passenger airbag systems use a compressed inert gas for inflation. The same precautions should be applied as with conventional airbag systems.
Rescuers should not be overly concerned about the possibility of contact with any airbag SRS chemicals. The two generants in common use are sodium azide and nitrocellulose. Prior to deployment of the airbag SRS, these generants are extremely well sealed within a strong metal container.
Sodium azide in its solid state is toxic. However due to the strong metal container, contact with it is extremely unlikely for rescue workers. In 1984 the National Highway Traffic Safety Administration (NHTSA), part of the US Department of Transportation, reported that both industry and the Federal Government had investigated and resolved health concerns relating to the use of sodium azide in airbag SRSs.
However, as in all other rescue operations, rescuers should wear gloves and eye protection. In the unlikely event that the container has ruptured, the generant will be found in pressed tablet form. Do not touch, ingest or expose the generant to an ignition source.
Nitrocellulose is not considered toxic and has no known irritating effects. A form of it is used mainly in the Eurobag Airbag SRS. In the unlikely event that the container has ruptured, the generant will be found in powder form. Do not expose the generant to an ignition source. Mix water with the powder to prevent ignition.
Once the airbag SRS has deployed, the vehicle interior may briefly appear to contain 'smoke'. This 'smoke' is actually a powdery residue that will settle on the surface of deployed airbag(s) and the vehicle interior. The powdery residue is cornstarch or talcum powder, which is used to lubricate the airbag as it deploys. The residue may also contain sodium compounds, mostly sodium carbonates (eg baking soda), and the interior air may contain small amounts of carbon monoxide. All of these are by-products of the generant combustion. There might also be a very small amount of sodium hydroxide that may be irritating to the skin and eyes.
NOTE: sodium hydroxide powder is slightly alkaline but is not considered toxic
Engineers and technicians regularly involved in airbag SRS crash tests have reported no ill effects from the products of airbag SRS deployment. In other tests on volunteers, the atmosphere produced by deployed SRS airbags, was found to pose no respiratory system hazard to chronic asthmatics.
The same gloves and eye protection rescuers wear normally, will prevent irritation due to sodium hydroxide. After handling a deployed airbag, rescuers should avoid rubbing their eyes, eating or smoking until they wash their hands with mild soap and water.
To identify a vehicle fitted with an airbag SRS, begin by checking for a "SRS" or "AIRBAG" moulded on the trim cover of the steering wheel hub and on the dashboard on the passenger's side. (Note: side airbags are not always visually identifiable.) There may also be a label or placard fitted to the following;
- underside of the bonnet
- sun visor(s)
- inside of the glovebox
- driver-side windscreen pillar
- driver-side or passenger-side 'B' pillar
- driver-side door
- lower corner of the windscreen
You can also check for a larger and more rectangular steering wheel hub (about 150 mm by 250 mm) which may indicate the presence of a driver-side airbag SRS. However, Eurobag or Facebag systems (eg BMW) are usually housed in normal sized steering wheel hubs.
In many cases vehicles fitted with an airbag SRS can be identified by comparing the Vehicle Identification Number (VIN) with manufacturer's data. Side airbags can be identified in this manner.
The list at the end of these guidelines includes airbag SRS identification data for most vehicles. Identification has been based on airbag SRS labels, placards or mouldings, and (where relevant) the VIN or part of the VIN. This list will be updated periodically.
Different types and models of airbag SRS have different methods of de-activation. For electrically activated systems, which have a back-up power supply, disconnecting the car battery (in accordance with the manufacturer's instructions) will begin the de-activation period for the back-up power supply. De-activation time for the back-up power supply may take a period of time ranging from seconds to minutes, depending on the system.
Simply turning the ignition switch to "OFF" may not de-activate the airbag SRS. The airbag SRS deployment mechanism may operate independently of the ignition switch. However, most systems will have a "safing"sensor that offers additional security against inadvertent deployment of the airbag.
Mechanically activated systems can sometimes be de-activated in the field.
The list at the end of these guidelines includes airbag SRS de-activation data for most vehicles. This list will be updated periodically.
When dealing with a vehicle fire, use standard fire extinguishing procedures first. Use any type of fire-fighting agent, including water. The gas generant is sealed in a watertight container. However, perform fire extinguishing procedures from the side of the vehicle and away from the potential deployment path of the airbag.
In the rare case of an interior occupant compartment fire, the airbag SRS module is designed to self-deploy if its internal temperature reaches approximately 175*C. The inflator will remain intact and operate normally.
NOTE: airbag SRS modules will not explode.
Towing a vehicle with an undeployed airbag SRS
Standard towing procedures are unlikely to deploy an airbag SRS. However, as a precaution when towing a vehicle with major frontal damage and an undeployed airbag SRS, safely disconnect the battery. Although generally good practice, be aware that this may not de-activate the system immediately, or at all with some types of airbag SRS.
Towing a vehicle with a deployed airbag SRS
When towing a vehicle with a deployed airbag SRS, follow the deployed airbag SRS precautions on page 8.
If a vehicle with an undeployed SRS is designated for scrapping, it is recommended that prior to scrapping, the airbag be safely deployed in accordance with manfacturers instructions
Remember an airbag SRS will deploy only in moderate to major frontal or near-frontal crashes. A frontal airbag SRS is not designed to deploy in side, rear, rollover, or less severe frontal crashes. For this reason, it is likely that you will be involved in a rescue from a vehicle with an airbag SRS that did not deploy.
An airbag SRS is unlikely to deploy during a rescue. On some vehicles there are two sensors that must close at the same time, therefore it is unlikely that rescue operations will result in a deployment. On many vehicles, the diagnostic module will also disable the airbag SRS if it detects crash sensor circuit "shorts" that exist for ten seconds while the ignition is "ON".
The metal combustion chamber in the airbag SRS module is sealed and protected. It is contained inside a permanently closed metal inflator located under the folded airbag that is behind the airbag SRS module trim cover. It is unlikely that the combustion chamber will rupture during a crash.
Never cut or drill directly into an undeployed airbag SRS module or attempt to take the module apart. This will avoid possible deployment and exposure to toxic chemicals. Do not touch exposed chemicals in the unlikely event the metal inflator canister of an undeployed airbag SRS module is ruptured or cut.
Rescue steps for undeployed airbag SRS
If the vehicle has been identified as having an airbag SRS (see page 4 for method of identification) the rescue steps are as follows;
- If possible, de-activate the airbag SRS (see page 5 for method of de-activation). When fully de-activated (including waiting for any specified de-activation period), rescue operations can be carried out as normal.
- While the airbag SRS is being de-activated, or if it is unable to be de-activated, the following rescue operations should begin immediately;
- DO move the seat of a stabilised occupant back as far as possible or lower the seat back.
- DO turn off the ignition.
- DO safely disconnect the battery. Disconnecting the battery immediately stops all power sources entering the steering column. Although good practice, be aware that this may not de-activate the system immediately or at all with a mechanical type.
- DO touch yourself to earth of the vehicle initially (if safe to do so) before contacting any bare wires
- It is important to appreciate the following during rescue operations with an airbag SRS that has not deployed and has not been de-activated;
- DO perform rescue efforts from the side of the vehicle and away from the potential deployment path of the airbag.
- DO keep your body or objects/tools off the airbag SRS trim cover and away from the front of an undeployed airbag.
The Drivers airbag expands 260 mm.
Passenger airbag 520mm
Side airbags 130mm wide and 300mm forward under the arm.
Curtain airbags 400 mm (down)
- DO NOT apply sharp blows to the steering column or dashboard if a vehicle is fitted with internal crash sensors, that is, a self contained system in the steering wheel. The list at the end of these guidelines includes data on system type for most vehicles.
- DO NOT cut into the steering column. Only cut the steering wheel rim or spokes. Do not apply heat near the SRS module, as this could cause the inflator to deploy (see page 5 for vehicle fire information).
- If the vehicle is fitted with side airbags avoid sharp blows to the door, seat or B-pillar areas.
If the airbag SRS has deployed, use normal rescue procedures and equipment. Do not delay rescue. There are no hazardous medical consequences for an occupant or rescue personnel from a deployed airbag SRS.
Wear the same gloves and eye protection that rescuers would normally wear. Protective equipment will guard against possible skin or eye irritation from the powdery airbag residue. Whether gloves are worn or not, wash your hands with mild soap and water after handling a deployed airbag.
Be aware of hot metal parts underneath the deployed airbag fabric. These components are located inside the steering wheel hub or behind the dashboard when there is a deployed passenger-side airbag SRS. These components are somewhat out of the way and should pose no threat.
NOTE: the airbag fabric, steering column, and steering wheel rim and spokes will not be hot.
Never cut or drill directly into an airbag SRS module or attempt to take the module apart. This will avoid exposure to toxic chemicals. Do not touch exposed chemicals in the unlikely event the metal inflator canister of an airbag SRS module is ruptured or cut.
Push deflated airbag aside for occupant removal. Airbags deflate at once after a deployment. There is no need to cover, remove, or repack the airbag during rescue operations.
Occupants can sustain minor skin redness or abrasions from contact with a deploying airbag, eg on the inside of the forearm or on the chin.
MYTH—Rescuers must wait 10 to 20 minutes before approaching a vehicle with a deployed airbag SRS, to allow for cooling and venting time.
FACT - Do not delay. The steering wheel rim and column, and airbag fabric will not be hot. 'Smoke' from a deployment should not be a concern.
MYTH - Disconnecting the car battery will deploy the airbag SRS in 15 to 20 minutes.
FACT—Disconnecting the battery cable will not deploy an airbag SRS. In fact, in most vehicles, disconnecting the car battery may begin de-activation of the airbag SRS by discharging to ground any stored energy in a back-up power capacitor.
MYTH—The airbag SRS will not deploy following disconnection of the car battery.
FACT - An electrical type airbag SRS is capable of deploying during the deactivation period of the back-up power supply following disconnection of the car battery.
In addition, a mechanical type airbag SRS may be capable of deploying at any time regardless of whether or not the car battery has been disconnected.
Delayed deployment is, however, extremely unlikely. The list at the end of these guidelines includes airbag SRS de-activation data for most vehicles. This list will be updated periodically.
MYTH—An airbag SRS contains an 'explosive solid' that can react like a cannon in a fire.
FACT—Today's airbag SRS modules contain a 'flammable solid', not an explosive. Rapid burning of the solid chemical inflates the airbag with inert gases. An airbag SRS does not explode in a crash or a fire.
MYTH - Rescue personnel may be overcome by highly toxic airbag SRS deployment smoke and dust.
FACT - Airbag SRS deployment 'smoke' is normal. The airbag is not burning or ruptured. Chemical analysis of the smoke and dust shows no reason for concern.
Tests conducted with volunteers; chronic asthmatics highly susceptible to airborne particles, showed that the atmosphere produced by a deployment posed no respiratory system hazard. The test engineers and technicians, who regularly handle deployed airbags and test dummies, have not reported ill effects from exposure to the deployments.
MYTH - The vehicle interior, airbag, and occupants will be covered in a hazardous residue.
FACT - Any powdery residue consists of corn starch or talcum powder and sodium compounds, mostly sodium carbonates (eg baking soda). Very small deposits of sodium hydroxide are also present. The powdery residue may irritate the skin and eyes, but poses no long term health hazard. The powder is slightly alkaline but is not considered toxic
Identifying an airbag SRS
- check for "SRS" or "AIRBAG" on steering wheel hub and above the glovebox
- check for "SRS" or "AIRBAG" on the sides of seats, the top of pillars or knee area to see if the vehicle is equipped with other airbag SRS items.
- check for a label or placard in the passenger compartment particularly on the sun visor or under the bonnet.
- check for a larger and more rectangular steering wheel hub.
Note - this does not apply to Eurobag system (eg BMW).
- compare the VIN number with manufacturer's data.
- refer to the vehicle list at the end of these guidelines.
De-activating an airbag SRS
- refer to the vehicle list at the end of these guidelines.
- use standard fire extinguishing procedures first. Carry out operations from the side of the vehicle, away from the potential deployment of the airbag.
- safely disconnect battery if the vehicle has an undeployed airbag SRS and has sustained major frontal damage. Be aware this may not de-activate the system.
- safely deploy the airbag in accordance with manufacturers instructions prior to scrapping.
Rescue with Pyrotechnic
The pyrotechnic module is generally located in the pillar but may be on the stalk
However, there are no visible markings on the seatbelt module to indicate if a Seatbelt Pretensioner SRS is installed on the belt.
There may be a label or placard fitted to the following;
- driver-side door
- passenger side door
- lower corner of the windscreen
In most cases vehicles fitted with a seatbelt pretensioner SRS can be identified by comparing the Vehicle Identification Number (VIN) with manufacturer';s data.
Rescue with undeployed seatbelt pretensioner SRS
The pyrotechnic charge of the pretensioner is not sufficient to pose a serious risk to rescuers unless it is tampered with.
If the pretensioner has not deployed DO NOT attempt to de-activate the SRS module. Instead, cut through the fabric of the seat belt. If the occupant must continue to be restrained prior to rescue, attempt to find an alternative means of interim restraint.
All rescuers in the close vicinity of the vehicle should be advised that the SRS has not deployed, as the noise generated from unexpected deployment can startle.
Rescue with Deployed Seatbelt Pretensioner SRS
It may not be readily obvious that the module has deployed, do not assume it has.
If the module has deployed, there is no further restriction to rescue attempts. However, the module should not be interfered with. It is recommended that the seatbelt be cut to allow removal of the occupant.
As per airbag SRS, perform fire extinguishing procedures away from the module of the pretensioner.
In the rare case of an interior occupant compartment fire, a pyrotechnic module may self-deploy with the increase of internal temperature. Deployment will pull an occupant back to an upright sitting position, which may cause further injury or distress. If at all possible, cut the seatbelt fabric to prevent pull back on the occupant.
Standard towing procedures are unlikely to deploy an undeployed pyrotechnic seatbelt pretensioner. However, seat belts should be either cut or fastened for towing.
As it is not always possible to confirm deployment of the seatbelt pretensioner, the vehicle should be treated as per undeployed vehicles.
There is a general misconception that airbags provide a soft cushion and will prevent bruising or other minor injuries in low severity crashes. This is incorrect—SRS airbags are designed to reduce peak loads on the head and chest in severe crashes (those where death or long term brain injury are possible).
When deploying, the airbag is firm, but it absorbs energy as the gases are released through the vents
While airbags significantly reduce the risk of serious or fatal injury in crashes, there are some risks from the deployment of airbags in low speed crashes. For this reason modern cars use a range of intelligent sensing functions to ensure that a crash is really happening (not just a bump in the road or a minor knock in the car park) and to fire airbags at the best time. This reduces the likelihood of airbags deploying in minor crashes.
Modern design and construction methods used in today';s vehicles include progressive crumple zones in the body and frame structure to reduce the rate of deceleration in severe frontal impacts. For this reason, damage sustained by a vehicle in a head-on collision may appear quite extensive and the airbags may not have deployed because the crumple zones have absorbed a significant amount of the energy of the impact.
In these cases, the airbag sensors have detected that the rate of vehicle deceleration has not been sufficient to require triggering of the airbags.
Typically, driver and or passenger airbags deploy in head-on collisions where the force of the impact is equal to or greater than striking an immovable and non deformable barrier (such as steel or concrete) at a speed of around 18 to 25 kph or higher. In offset collisions or in a head-on collision with another vehicle or other deformable and or movable object, the speed would generally need to be significantly higher than 25kph for the airbags to deploy
Airbags designed for frontal impacts usually do not deploy in rear end collisions, side impacts, rollover accidents or in most underride accidents.
In addition to frontal impacts as described above, airbags may deploy in cases where:
- a moderate to severe impact has been sustained by a vehicle';s undercarriage such as when striking an elevated median strip or kerb,
- a wheel has struck a deep (severe) hole or pothole, or
- when driving down a very steep slope and the front strikes the ground at the end of the slope.
Damage to vehicle body panels may appear relatively minor in these cases.
Owners should refer to their vehicle Owner';s Manual for further explanation of airbag deployment parameters and characteristics.
The following list gives airbag SRS identification and de-activation information on a model-to-model basis. Before inclusion, each model entry has been agreed to by the manufacturer. If a particular model has not been included in the list, do not automatically assume that it is not fitted with an airbag SRS. The information may not have been available at the time of publishing.
The Department of Infrastructure, Transport, Regional Development and Local Government intends to update this list periodically.
|Make||vehicle make and model.|
|Airbag fitted||D = driver-side, P = passenger-side, S = side (front or rear),
W = window (head curtain), * = optional, X = none
|Type||electrical, mechanical and whether fitted with internal sensors (self-contained system) or external sensors.|
|Fitted from||first date fitted to vehicle.|
|VIN||Vehicle Identification Number or relevant part of it.|
|VIN position||position position of VIN plate on vehicle.|
|Identifiers||SRS airbag labels, decals, placards etc.|
|De-ac period||time period for airbag SRS system to de-activate.|
|De-ac method||method to start de-activation.|