What types of flue spaces are in pallet rack systems?
Longitudinal Flue space is the clearing or spacing between back-to-back rows of pallet rack. In other words, the longitudinal flue space is the space or distance between two back-to-back rows of pallet rack. Typically, pallets are loaded too far back on the rack in both back-to-back rows or product becomes dislodged which blocks the flue. With proper warehouse rack spacing and flue protection this can be avoided.
Transverse Flue spaces are known as the space or gaps between the pallet load and the upright frame of the rack. Typically, if pallets or boxes are stacked less than 6″ from other pallets they are blocking the transverse flue space. The racks upright frame is not considered as open or part of the flue, and therefore requires 3” of open space on both sides of the frame.
What testing and research has been done on flue spaces in pallet rack systems?
Within the past decade, the National Fire Protection Association (NFPA13) as well as FM Global started conducting “live fire tests” to determine the safest design for warehouse rack spacing for storage systems in the event of a warehouse fire. Many benefits were found when flue spaces were maintained between the pallets stored on the racks. Racking systems with 6” flue spaces between pallets, both in the longitudinal and transverse direction had the following benefits:
- Property loss reduction through quick activation Early Suppression Fast Response (ESFR) sprinklers
- Improved penetration of sprinkler water to all levels of inventory
- Faster activation of smoke and heat vent systems
- Improved safety of employees, fire fighters and warehouse
The NFPA13 Code was updated to include sections that required that flues be “maintained” in all warehouse racking systems. The International Building Code (IBC2012) was also changed to reflect the new findings. The code requires that the 6” flue spaces be maintained for all warehouse racking spacing. It authorizes the Fire Marshalls at the local level the choice to mandate a “mechanical means of separation” such as pallet stops, if they so choose.
Many Fire Marshalls around the country are now changing their High Pile Guidelines to mandate pallet stops on all new racking projects. In those cases, pallet stops must be installed in order to meet the local requirements for permits. In some cases, existing warehouses that have violated the code are also being ordered to retrofit their pallet racks with pallet stops to meet warehouse rack spacing requirements.