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  1. #1
    MembersZone Subscriber rmoore's Avatar
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    Default The Airbag That Does Not Need Electricity

    I recently had another opportunity to cut up two older Volvo sedans. What is interesting about these cars is that they had Volvo's original seat-mounted, side impact airbag systems. From 1995 through model year 1997, the first Volvo seat airbags did not use electricity to deploy. These bags, referred to by Volvo engineers as their 'mechanical' airbags, deployed using a plunger-type mechanical deployment mechanism.

    When struck on the side, the door would move inward. A rigid component inside the door would cause the door to crush into a small plunger mounted low along the outboard side of each front seat. Once punched in, this plunger would fire off a pyrotechnic powder charge, causing the blast that actually resulted in the seat airbag deploying.

    Although 1995 to 1997 Volvo cars are not that prevalent, what is important to note is that if one is encountered, shutting down the 12-volt electrical system DOES NOT make these seat airbags any less likely to accidentally deploy. In fact, when I conduct airbag deployment demonstrations, I simply open the door, take a flathead axe, and strike the plunger. The seat airbag deploys with just a medium hard hit from my tool.

    First image is how the interior trim will look normally. This is a 1997 Volvo 850 sedan.

    Second image shows the SIPSbag cover removed, exposing the plunger actuator.
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    Last edited by rmoore; 03-11-2012 at 07:09 PM.
    Ron Moore, Forum Moderator
    www.universityofextrication.com


  2. #2
    MembersZone Subscriber rmoore's Avatar
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    Default

    Close-up shots of Volvo's 1995-1997 mechanical seat airbag system shows a bit more detail of the plunger and the orange-colored warning sticker that wraps around the plunger device.
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    Ron Moore, Forum Moderator
    www.universityofextrication.com

  3. #3
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    Default

    Good post Ron

    Whats interesting here is that it will be very difficult if impossible pending rescuer vehicle knowledge that we would be able to tell the difference between mechanical and electric systems.

    Cutting the SRS wiring with insulated wire cutters is one way to make them safe, the percussion cap as stated will only actuate if there is an impact on the cap, if the wiring is cut this will stop the bag deploying.

  4. #4
    Forum Member dragonfyre's Avatar
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    Default

    Ron: I've mentioned that in my class for years. Volvo actually sent me instructions to disable them and tell you to cut the cable after removing the plastic housing.
    Steve Dragon
    FFII, Fire Instructor II, Fire Officer I, Fire Appartus Driver Operator Certified
    Volunteers are never "off duty".
    http://www.bufd7.org

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  6. #6
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    Default

    Thanks for the posts everyone. I have read about these and understood the concept of Mechanically Activated Airbags but this is the first video I have seen.

    So here is my question. What is the best way to identify these Airbags once on scene?

    Additionally how do we effectively eliminate the danger? It seems to me that it is a fairly specialized thing to accomplish.

    Thanks

    Reid

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