Flue Spaces: Guidelines & Best Practices for Your Rack System

A properly designed pallet rack system should allow for flue space between pallet loads and upright frames. This design element safeguards your inventory and serves as a safety measure against fire damage.

What is flue space?

The National Fire Protection Association (NFPA) defines flue space as clear vertical openings from the floor up to the ceiling within rack storage areas. Flue spaces are a Fire Code requirement because they reduce the damage from a fire delay by allowing heat to ventilate upward and activate the sprinkler systems quicker. They also allow the sprinkler water to penetrate down throughout the racking system.

There are two types of flue spaces: transverse flues and longitudinal flues. Transverse flue space refers to the space between pallets, and between pallets and uprights, within each row that run parallel to the loading direction. They are the gaps one sees when standing in the aisle. Longitudinal flue space refers to the space between multiple rows of racks. This is the gap one sees at the end of the aisle.

Flue Space Guidelines

The guidelines for flue spaces can vary depending on your local building codes. Usually, all racking arrangements at all heights require transverse flue spaces.
Longitudinal flue spaces are required in a double row rack when the storage height exceeds 25 feet.  Any system under 25′ does not require longitudinal (vertical) flue spacing but you should confirm with local fire departments.

Flue spaces, regardless if they are longitudinal or transverse are to be a minimum of 6”. These flue spaces shall run the entire height of the rack, from top to bottom. The code mandates storage aids if the flue is not being maintained. These aids are designed to provide some barrier or restraint to assist in keeping the space open.

How to Achieve Correct Flue Space with Flue Keepers

A storage aid restricts pallet loads from intruding into the required vertical opening. A properly designed racking system allows pallets to hang over the back beam in a double row to maintain adequate longitudinal flue space. It is possible for these pallets to be pushed too deep so that they about each other. Row spacers are often installed to maintain accurate flue spacing between rows.

Flue keepers can be attached to the uprights to maintain correct transverse flue space. The flue keepers will prevent pallets from impinging into the transverse flue space.

Other Factors to Consider

Using open decking, instead of solid decking, allows the sprinkler system water to be able to penetrate throughout the entire rack system and discourages the horizontal spread of flames. Wire decking, punch decking or snap shelf decking are decking options that provide a 50% open design.

Get More Information

Your racking system should be properly designed to meet your local fire and building codes. This is especially important when considering flue spacing. A qualified specialist should review any design and layout considerations to make sure your system adheres to the NFPA’s requirements.
This case study provides an example of how the design of your system can be tailored to meet the needs of your operation.

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