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The InchWorm Technique

Updated: Jun 12

Background

When I started learning about confined space rescue I was shown a technique using a mechanical advantage system called the “Inchworm Technique.” This technique, shown on that course, used a pre-built 4:1 mechanical advantage system on 12.5mm static kernmantle rope. The rescuer would take the system into the space and use it to pull a patient horizontally. It could be rigged to a temporary anchor in the space, a remote anchor extended into the space (rope), or the rescuer’s harness. The system may have to be reset numerous times to cover the required distance and extricate the patient, hence the comparison to an “inchworm”. This system has its advantages in tight spaces with large patients that need substantial horizontal movement towards a vertical or offset exit. As all of the spaces we trained in were large enough to physically pull a patient, and we were all young, fit rescuers, no one utilized the technique regularly. Like most things you spend very little time on, the Inchworm Technique was relegated to the back of my mind.

Fast forward many years later. We were working for a company that was hired to assist gas fitters to check the crawl spaces in close to 100 educational institutes for pipes that may have shifted and therefore be leaking. Due to the policies of the client, the risk of gas leaks, the convoluted nature of the spaces and the condition of some of the workers, it was decided to send a rescuer with the maintenance team into the spaces. We went and did our recce (recon for our friends south of the 49) and found that some of the spaces we needed to enter had to be breeched and were only 18” in height. Throw in the rough dirt floors we had to traverse and viola – the Inchworm Technique came back to the front of my mind.

We equipped our rescuers entering the spaces with a backpack that carried amongst other items – a small mechanical advantage system (AKA a jigger) to allow the rescuer to use the Inchworm Technique. We decided to try a few different packs (because we are all gear geeks at heart) and used both the Conterra LS Response Pack and the Maxpedition Falcon II. On a side note, these packs were used in some very damaging conditions (sliding on concrete and dirt floors, entering through small spaces) and both packs exceeded all expectations. We still have both packs in service 4 years later. For the inchworm we constructed two different jiggers. One was the Rock Exotica Aztek System and the other was a home-built mechanical advantage system using CMC Protech double sheaved pulleys. Both mechanical advantage systems were rigged with 8mm cordage with a 5mm capture prussic.

While we never had to put the inchworm technique into practice on an actual rescue, during this project we did do some scenario-based training with it. Since the rescue system was not “seeing” a fully suspended load, the anchoring options became easy. We could use the wood framing – a bar spanning some of the entrances we had to breech through cement blocks – the rescuer, and stakes in the dirt floors as anchors. We found the Aztek with its swivel pulleys was slightly more cumbersome to deploy, but pulled the load in a nice fashion. The non-swivel pulleys deployed quicker from the bag, however, some thought was required to ensure you did not rig the system in such a way as to cross the lines. Both systems were extremely effective in removing a patient from the spaces we were in.

Inchworm Setup on a Rope Anchor

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#confinedspace #inchworm #mechanicaladvantage #reset

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