To ensure sprinklers provide optimal fire suppression, it’s critical to leave adequate rack flue spaces around stored products. That’s because the majority of new warehouses built today include overhead sprinkler systems installed close to the ceiling.

These early-suppression/fast-response (ESFR) systems adhere to local building and fire codes’ requirements. These mandate adequate coverage in the event of a fire, regardless of the building’s ultimate use. When an operation installs storage racks, these same jurisdictions frequently refer to the guidelines for fire sprinkler design and building codes.

Rack Flue Spaces Recommended in Building Codes

These recommendations come from three separate governing bodies:

One of the most important aspects of successful fire suppression by overhead sprinklers is to provide spacing around all four sides of each pallet load. Spacing side-to-side within the bays and around the rack columns is known as the transverse flue space. Spacing back-to-back in double row pallet rack systems is called the longitudinal flue space.

Current fire codes mandate that open flues spaces must be provided between pallets in the transverse and longitudinal (down-aisle) directions, or possibly both. The exact size (typically 6 inches wide), location and placement of the flue spaces can vary depending on the type of rack, overall storage height and sprinkler coverage provided. If a product encroaches into this space and obstructs the opening, then heat from the fire cannot rise to the ceiling as quickly — delaying the initiation of the sprinklers. Furthermore, obstructed flue spaces prohibit the flow of water from the sprinklers through the racking, reducing the chance of a fast fire suppression.

Train Forklift Operators To Maintain Open Flue Space

Transgressions into transverse and longitudinal flue spaces are often the result of inadequate training of forklift drivers. One best practice is to ensure that all personnel are educated on the importance of these openings and trained to alert a manager about a situation that needs to be corrected should one be observed.

Another reason for the obstructions could be the placement of larger pallet loads (or product overhang) than the racking was originally designed for into the structure. For example, a rack designed to hold two, 40-inch-wide pallets in one bay with adequate transverse flue spaces may be able to hold two, 44-inch-wide pallets — but with far less open space around the loads. That’s another safety reason for why it’s important to match the pallets to the specific design of the rack.

Rack Accessories Help With Spacing

To increase the likelihood that open spaces remain unobstructed, some facilities place bright yellow labels on the beam faces. The labels align with the transverse flues. This creates a visual reminder for forklift operators as they place loads into the rack to maintain clearance on the sides and the back.

For further protection against flue space obstruction, accessory devices that project into the sides of the bays. The devices mount to the rack columns and between the beams on double row pallet rack systems. Both accessories prohibit pallet loads from extending into the flue spaces. Transverse flue space devices on the sides guide pallets into place. The longitudinal flue space device prevents the load from extending too far over the back beams.

Certain jurisdictions are now requiring the use of these devices in new rack structure building permits. This gives the overhead sprinkler system the greatest chance of successfully and quickly suppressing a fire. That, in turn, reduces the risks of damage and death. The inspecting authority can also retroactively require the devices if obstructions constantly block the flue spaces.

Get More Rack Fire Suppression Information

Looking for more details about integrating fire suppression systems and storage rack? Find additional details in the “Building Departments and Fire Codes” section of RMI’s frequently asked questions (FAQs) page.