There are many fire hazards commonly present in warehouses beyond the obvious presence of high combustible loading from rack and palletized storage arrays. In Part 1 of our Warehouse Fire Hazards blog series, we took a look at High Intensity Discharge Lighting. In Part 2, we will review idle pallets and the significant hazard they pose in warehouses.

Pallets are flat platforms made of wood, plastic, metal, or composite materials that are designed to provide access for forklifts, pallet jacks, and other material handling equipment. Pallets serve an important function in warehouse and distribution operations, allowing goods to be moved, stacked, and stored with ease and speed, and they can have a big impact on safety and loading/unloading times in the supply chain process.

Once a pallet has been relieved of its product load, it becomes an “idle pallet” until it is needed again. In a warehouse or distribution facility, the volume of idle pallets at any given time can be significant.

Storage of idle pallets presents a serious fire hazard. Geometrically, a stack of idle pallets creates almost perfect conditions for an intense fire with ample air supply to many surfaces, allowing a fire to grow rapidly.

Check out the interactive map below to find out about some of the wood pallet fires that have struck the United States from 2011 through 2013. Click on the red flame to find out more about each fire:

A fire involving idle pallets will have a high heat release rate, creating a high-velocity plume of gases that can push sprinkler droplets away from the fire. The high temperatures generated by the intense fire can evaporate the water droplets before they reach the seat of the fire to cool the burning material. The fire will continue to grow, opening more and more sprinklers, until the sprinkler system’s water supply is overtaxed and a total loss of the warehouse may occur.

Wood pallets become dry and frayed, making them easy to ignite. Plastic pallets have become a popular alternative to traditional wood pallets because they offer pest resistance, superior hygiene, durability, lighter weight, and sustainability (recycling). Unfortunately, plastic pallets have a heat release rate three to five times higher than wood pallets, and therefore pose a greater hazard than traditional wood pallets, with the exception of plastic pallets that are Factory Mutual (FM) Approved. FM approved plastic pallets offer a fire resistance equivalent to wood, and where utilized, they can be protected in accordance with the requirements for wood pallets.

It is critical to recognize the fire hazards that idle pallets pose, and fully evaluate the idle pallet storage location and arrangement to determine the sprinkler protection needed. Next week, in the continuation of this post, we will review the protection requirements for idle pallet storage in the National Fire Protection Association’s (NFPA) codes and standards, as well as FM.