|The truck is lowered onto the wood cribbing. (Jerry Slagle Photograph)|
|The plastic cribbing is in place.|
|North Fork’s Engine 1, a 1984 Ford Darley, was used in the cold weather comparison of plastic and wood cribbing. (Jerry Slagle Photograph)|
Cribbing is arguably the most overlooked and often underused part of vehicle extrications and other rescue operations. Let’s face it; do we ever really have enough cribbing? When space on the rig is a concern, isn’t cribbing one of the first things to go?
Here in the United States, most fire departments carry a complement of wood cribbing. Wood is relatively inexpensive and traditionally easy to come by. Many departments make their own cribbing and step chocks.
Generally speaking, 4×4 blocks, 2×4 blocks, wedges and layered 2x6s for step chocks do the basic trick. For larger rescue ops and shoring, departments will carry longer and larger lengths of raw material to be cut on-scene, as the job requires.
Is wood the best way to go? In considering that question, I am reminded that a number of years ago, we placed our patients on wooden backboards. At that time, many departments (mine included) made their own backboards, just as they make their own cribbing. When the biohazard and bloodborne pathogen concerns over wooden backboards arose, the end result was no more wooden backboards.
Doesn’t wood cribbing have the same characteristics as wood backboards? Isn’t wood cribbing exposed to the same body fluids and toxins as the backboards were? The answer to these questions is a resounding “yes,” and it’s a real firefighter personal safety concern that should be taken very seriously. I’ve used wooden cribbing for years, but admittedly didn’t give enough attention to the exposure concern until now.
In many other countries, where wood is less available, plastic cribbing is now used almost exclusively. Most of the plastic cribbing manufactured in the U.S. is made by Turtle Plastics of Ohio out of recycled milk jugs and other plastic recyclables. The raw recycled plastic is first pelletized and then heated and compressed into the final cribbing pieces. RESQTEC makes plastic cribbing in Europe, and sells it here in the U.S. as well.
There is plenty of existing test data that compares wood cribbing to plastic cribbing. Some of the most field-applicable results include considerations such as: wood is porous (biohazard concerns); wood is irregular in makeup; and wood is prone to splitting, splintering and knots, depending on the type.
Potential For Slippage
Wood is also relatively inexpensive and readily available in most areas of the country. Users of wood cribbing are limited to standard dimensions (2×4, 4×4, 6×6) of commercially-sold wood products.
Plastic cribbing is more expensive than wood, but it is also nonporous, impervious to fluids and will typically hold two to three times more weight than wood. Plastic cribbing can be manufactured in any dimensions. I know of at least one company that warrants its plastic cribbing for 50 years. I am unaware of anyone who warrants wood cribbing.
Firefighters debate this issue on a number of blogs. The most common concern involves the potential for slippage of plastic cribbing in cold, snowy and icy conditions. The question offered a good opportunity to do some testing. Here in the Northern Rockies, we have lots of time in snowy, cold, wet and icy conditions.
I asked for help from the Idaho State Search and Rescue’s Extrication Team (Salmon, Idaho), and from the Gibbsonville station of the North Fork Fire Department to test different types of cribbing. The vehicle used for the test was a 1984 Ford Darley fire engine, weighing in at 31,000 pounds. The testing was done on March 6, 2010, at 0930 in 12-plus inches of snow on a gradual slope. The temperature was in the low to mid 20s.
The crew was charged with the task of lifting, with airbags, the front tires off of the ground, cribbing the front end of the apparatus, and letting the truck back down onto the crib stacks. One side of the engine was to be cribbed with wood, and the other with plastic. Sample pieces of plastic cribbing were provided by Turtle Plastics, while the wood cribbing was provided by Salmon Search and Rescue.
After digging out the snow down to ice, the initial wood cribbing (deck pieces) were found to slide more on the ice, particularly on the painted side, than the plastic.
The plastic cribbing had small pyramid-shaped protrusions on opposite sides and “Lincoln Log” type ridges on the other two sides. The pyramid-covered sides seemed to “bite” into the ice and snow better than the smooth-sided wood cribbing. The crew noted that if the plastic had been smooth-sided, the sliding issue would have been the same for both.
As the crib towers were erected, comments were made about the plastic pieces interlocking into each other on both the pyramid sides, as well as the Lincoln Log sides. This interlocking seemed to make the plastic tower hold fast once placed, while the wood tower pieces moved freely on each other in the absence of weight to hold them in place.
As the engine was lowered onto the crib towers, the most noticeable difference was the noise that emanated from the wood stack, with the typical creaking and settling that occurs with frozen wood in these situations. The plastic stack made no noise.
Crew members noted that the truck’s frame member “bit” into the wood wedges, giving them confidence that they would not spit out of the stack. Although the plastic wedges remained in place, the plastic seemed to be harder and, as such, less susceptible to the same “bite” into the wood wedges. Overall, the plastic cribbing was found to be the preferred choice for the towers, with the wooden wedges winning out over the plastic ones.
I can see how a simple addition of ramped ridges onto one side of the plastic wedges could eliminate the chances of slippage.
In the end, I’m sure that choices for cribbing will continue to be based on budget, space on rigs and availability. Please be sure to remember the biohazard concern associated with wooden cribbing. As with wooden backboards, contracting an unwanted disease or illness from an infected splinter or sliver of wood is not worth the cheaper price of wood, at any cost.
Editor’s Note: Carl Haddon is the national training director for the 5 Star Training Academy sponsored by Volvo North America and Champion Rescue Tools and serves as a deputy fire chief and fire commissioner for the North Fork Fire Department in Idaho. He is a career veteran of more than 25 years in the fire and EMS service in southern California and has served since the early 1980s as a fire/safety director for numerous racing organizations, including Penske Motorsports, NASCAR, USAC and Mickey Thompson Racing. He is a certified Level 2 fire instructor and teaches auto extrication classes across the country.