While constructing box cribs, each piece of timber should overlap the next piece by a minimum of four inches (see Photo 5). This overlap helps maintain the integrity of the system in the event that a particular piece shifts slightly. This overlap also comes into play when determining the maximum height for building a particular box crib. The standard rule for a square box crib is that the height should be only three times the width of the base.
Height to Width Ratio Math
The timber being used is 24 inches long with an overlap of 4 inches on each end.
- 24 inches – 8 inches = 16-inch base
- A 3:1 ratio is used only when the system is a square box crib.
- 16 inches x 3 = 48-inch maximum height
- A 1:1 ratio should be used if the crib is not square.
Members should ensure they have sufficient cribbing readily available for the incident. This includes having enough for the crib stacks supporting the air bags, as well as to crib the load when lifted. It is always preferable to have extra cribbing available in various sizes.
Initial Size-Up & Rescue Plan
Upon approach to the scene, members need to start sizing up several things: what is the status of the victim, what is causing the victim to be trapped, how is the victim trapped and what are the potential plans for extrication? These details must be carefully considered to guarantee a safe and efficient operation.
After scene safety issues are addressed, members must determine the status of the victim. Is the victim alive or deceased? Is the victim potentially viable if removed rapidly? This information helps ascertain whether members are operating in a rescue mode or a recovery mode. Members can slow down and methodically attempt the extrication process if the incident is deemed a recovery.
Once the operational mode is established, it is essential that members concentrate on figuring out exactly how the victim is trapped in order to devise the optimal extrication plan. This incident could involve having an extremity stuck in a machine or an entire torso pinned under a vehicle. Members should estimate how much movement will be required to free the victim.
Members must determine the size of air bag that will be needed to accomplish the extrication (see Photo 6). The size of the air bag is dictated by the weight of the object, the potential lift points, the space available for placement of the air bag and the predicted amount of movement required. A sturdy lift point that can support the weight of the object must be selected. It is critical to remember the substantial impact that surface contact has on the lifting capacity of the air bag. A lift point that can support the object does no good if the surface area is so minimal that an air bag cannot lift the objective. See article two in the series for more information on lifting capacities.
Proper size-up is critically important for a successful operation involving an air-bag lift. Members must assess and attempt to remove or lessen any hazards that exist, which includes cribbing any unstable loads. After the scene is deemed safe, members must determine a logical plan for extrication of the victim. These initial actions will help prevent further injury to the victim and will make for a safer and more efficient operation.
JONATHAN HALL is currently a firefighter with the Saint Paul, MN, Fire Department. He previously served as a training and safety officer for the Township Fire Department in Eau Claire, WI. He is a certified fire instructor for the Chippewa Valley Technical College in Eau Claire. Jonathan frequently teaches firefighter survival and rapid intervention team concepts in both Minnesota and Wisconsin.