Photo by Mickey Conboy Volvo introduced Side Impact Protection System (SIPS) airbags in 1995 on most 850 models. The airbags are now also featured on all 850 and 960 models.
Photo by Mickey Conboy How Volvo's side-impact bag works.
Vehicles equipped with SIPS are identified with an icon or decal in the lower left corner of the front windshield and the front seat side pockets (see photos 2, 3 and 4 on this page).
Side-impact airbags are located in both front seats. They operate independently of each other and independently of the front airbags. The SIPS must be disarmed independently of each other and of the front airbag system. Procedures for disabling the SIPS will be discussed in this article.
Let's look at the difference between SIPS airbags and front airbags. A front airbag consists of a power supply (i.e., the battery), a crash sensor (independent or consolidated into the computer) and a computer to process the impact and send an electric current to the airbag inflator. Cutting the power to the system (disconnecting the battery) will deactivate the airbag. However, because side-impact airbags operate independently of front airbags, cutting the vehicle's power will not disarm the side-impact airbags.
The side-impact airbag consists of three major components:
- The sensor unit.
- The pyrotechnical firing device.
- The cushion module (airbag).
The sensor unit contains a small detonator cap that triggers the pyrotechnical firing circuit. The sensor unit is located on the seat frame between the rocker panel and the front seats, approximately at the center of the seat rail (see photo 5).
The pyrotechnic firing device connects the sensor to the cushion module (airbag). It is made up of two plastic tubes that are encased in a ribbed-black protective sleeve (see photo 6). The chemical in the plastic tubes is made up of approximately two grams of nitro-cellulose (gunpowder).
Photo by Mickey Conboy Photo 7
The cushion module (airbag) is located on the seat back frame and is fired by two gas generators (see photo 7). Note: A side-impact airbag deploys eight times faster than a front airbag.
Disarming A Side-Impact Airbag
During an extrication, it is possible to activate the side-impact airbag, even if the battery is disconnected. Therefore, it may be necessary to disarm the system.
Never use any tools, even manual tools, near the sensor unit before disarming the SIPS. The easiest way to disarm the system is to locate the seat side pocket and remove it (see photo 8). On the Volvo 850, you should pull up on the front of the pocket and then slide it back. On the 960, it will be slightly more difficult, because the pocket is held in place by two screws.
For the access needed, grab the back of the seat pocket and firmly pull it away from the seat. It will probably break where the screw attaches to the seat. Remember, do not use any tools for these procedures. Locate the ribbed-black plastic sleeve containing the two pyrotechnic firing circuits (see photo 9) and simply cut the sleeve. (Some have suggested that rescuers locate the ribbed-black plastic sleeve containing the two pyrotechnic firing circuits by reaching between the seat bottom and the seat back at the outside seat corner but this will be extremely difficult with damage to the vehicle and an injured victim in the seat.)
Another pyrotechnic device to be aware of is the Volvo seatbelt tensioner. The driver and the passenger front seats on all Volvo models with Safety Restraint System (SRS) airbags from 1993 on are equipped with pyrotechnical seatbelt tensioners. They are located in both B-posts and are fired when the front airbags are deployed. This does not include the side-impact airbags. Some seatbelt tensioners, such as those on the 850 models, are located in the center of the B-post and fire down (see photo 11). Others, such as those on the 960 models, are located at the bottom of the B-post, near the rocker panel, and fire up (see photo 10).
The seatbelt tensioners have a gas generator with an electrical ignitor connected to a cylinder. Inside the cylinder is a piston with a wire, one side of which is wound around a drum connected to the seatbelt reel. An electrical signal from the SRS computer activates the gas generator and the gas produced drives the piston into the cylinder. The cable is tightened and takes up any slack in the seatbelt.
Seatbelt tensioners are deployed only with the front airbags. If the front airbags are not deployed, the tensioners are live and in the B-post. In order to disarm them, simply disconnect the battery. The battery must be disconnected during an extrication, even if it is smashed or broken, since it only takes a fraction of a volt to fire SRS components (airbags included).
Photo by Mickey Conboy Photo 11
After disconnecting the battery, it is advisable to expose the seatbelt tensioner in the B-post, if the B-post is to be cut or moved in any way in order to avoid cutting into the electrical ignitor and gas generator.
In a normal undamaged car, the seatbelt poses little hazard to the firefighter because it is anchored to the B-post. But in a damaged vehicle, where there is a side impact, or a B-post cut or folded by firefighter, there is danger. Always remember to disconnect the battery.
How does this information affect the rescuer? It is my opinion that normal extrication techniques should not be changed. It is simply necessary for the rescuer to be more aware of what he or she is working on. Proper evaluation of the situation will dictate what precautionary measures are to be taken.
Richard Chiaramonte is a firefighter in Middlehope, NY, a New York State certified instructor and an instructor at the Orange County, NY, Fire Training Center. He has been a Volvo mechanic for 10 years.
