Pressurized Vessels On Vehicles: Part 1

Subject: Pressurized Vessels on Vehicles - Part 1

Topic: Extrication Challenges

Objective: Identify the extrication challenges presented by pressurized vessels on vehicles

Task: Describe the procedures for safely accomplishing vehicle extrication tasks when working in the presence of pressurized vessels

Emergency responders are increasingly confronted with pressurized vessels on vehicles. These pressurized containers pose a risk to responders when dealing with a vehicle crash with extrication or when arriving at a vehicle fire incident. This four-part University of Extrication series looks at the rescue and fire suppression hazards of these pressurized vessels that we encounter at the emergency scene and presents safety-oriented information on how to deal with this challenge.

Pressurized vessels on vehicles may be large or small; long or short; visible or hidden within the structure of the vehicle. Pressurized vessels on vehicles can be a component of the vehicle's energy-absorbing bumper system or the unit may serve as the "hinge" for the trunk of a vehicle.

These pressurized containers are increasingly found on new model vehicles serving as lifter struts for the hood instead of the standard hood hinge. These struts may also assist in opening the vehicle's rear hatchback, liftgate or liftglass unit. A hatchback is a one-piece unit at the rear of a sedan vehicle containing a permanently mounted rear window glass that exposes the entire rear area of the vehicle when opened. A liftgate is a unit at the rear of a sport utility-type vehicle containing the rear glass and the solid rear portion of the vehicle. When the latch is released, the liftgate opens towards the roof. A liftglass is also a unit at the rear of the vehicle; however, it consists of only the rear window glass. When the liftglass is opened upwards towards the roof, the rear liftgate remains closed.

Part 1 of this series addresses the extrication challenge of having pressurized struts attached to the liftglass or liftgate of a damaged vehicle in a situation where extrication is required. When breaking the rear liftgate glass, the responder should first size-up the rear liftglass unit to determine if there are any black "buttons" on the glass. If there are, then it should be anticipated that the pressurized lifter struts will also be attached to the glass.

When the liftglass is closed, the struts are at their near maximum pressure. When the glass is broken, expect the struts to quickly expand, extending out to their full length. Remain clear of the window area as the struts expand.

If a total roof removal evolution is to be accomplished, personnel should again size-up the vehicle and attempt to determine if pressurized struts are present on the rear liftgate, liftglass or hatchback unit. It is possible for up to four struts to be present; two for the liftglass and two for the liftgate assembly. It is preferable that these struts be removed when beginning the task and not cut through during total roof removal. After removing the glass, any struts that are visible should be pried off their mount at one end and left to harmlessly expand. Ideally, rescue crews should open the rear liftgate or hatchback prior to cutting the rear roof pillars. This moves the struts harmlessly out of the way and also reduces the amount of material that must be cut through to remove the roof.

Besides unexpected movement of the struts or the hatchback since cutting is done at the rear of the vehicle, it is possible that cutting equipment can sever the pressurized strut. Again, this is not the desired result and is something that should be avoided if possible during roof removal. As our cutting equipment closes in around a pressurized strut, the strut will fail. Experience has shown that depending upon the point where the cutter fractures the strut's outer walls and based upon the size and design of the strut itself, cutting into the strut can cause a high-pressure fluid leak or can cause the metal strut to "explode" in an uncontrolled manner. Both of these events are dangerous, expose rescuers to risk and should be prevented.

Avoid strut cuts

This series on pressurized vessels in and on modern-day vehicles will continue with Part 2 looking at fire suppression challenges of hood hinge struts. Several recent cases of firefighter injury due to exploding hood struts during engine compartment fires will be featured.

Part 3 will address fire suppression challenges due to stored gas airbag inflator modules. A vehicle fire where the passenger frontal airbag inflator cylinder flew forward over 30 feet will be presented. Part 4 will explain the fire suppression challenges of pressurized struts designed into a vehicle's energy absorbing bumper system.


Ron Moore, a Firehouse contributing editor, is a battalion chief and the training officer for the McKinney, TX, Fire Department. He also authors a monthly online article in the Firehouse.com "MembersZone" and serves as the Forum Moderator for the extrication section of the Firehouse.com website. Moore can be contacted directly at Rmoore@firehouse.com.

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