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  • Jerry Schultz, P.E.

Throughout the writing of this blog, one subject that I have gone back to time and time again, is solid shelving. You would think that at some time, the issue would be resolved and the revisions would stop. The 2022 edition of NFPA 13, Standard for the Installation of Sprinkler Systems is proposed to be revised again to address solid shelving, but this time in multiple-row racking. The proposed changes have been approved by the committee and are out for final review by the general public. The only possibility to change the document now is by submitting a Notice of Intent to Make a Motion (NITMAM) and then have a floor vote at the annual meeting. NITMAM’s have to be filed by February 17, 2021.

In 2016, I wrote a blog post (Fire Testing, January 18, 2016) where I noted that there were no new tests presented to the committee as justification for the initial solid shelving changes to the standard that happened in 1999. In a nutshell, those earlier changes defined solid shelving and set an area limit for a solid shelf before requiring in-rack sprinklers. As time progressed and additional revisions took place, it became obvious that the committee was saying that the load itself defines if solid shelving is present and not whether or not shelving material is present. The committee reviewed tests that were conducted in the 1970’s and reinterpreted the results. This cycle, the proposed change to the solid shelving requirements once again is based on interpretation of a test conducted in the 1970’s. At that time, the test protocol only tested 16 foot deep racks. Not being involved with these tests, I do not know why that was what they tested. These racks could have been common in the industry or even more likely, that is the rack they had available. I cannot state why they only tested 16 feet deep racks.

The present committee reviewed that earlier test data and felt that since the test was limited to a given depth there was a need to change the standard. Hence the solid shelving requirements are being modified again. Three options are proposed -- provide transverse and longitudinal flues (longitudinal flues have never been required in multiple-row racking), limit the depth of a multiple-row rack, or provide in-rack sprinklers.

Several cycles ago, it was recognized that since a longitudinal flue was not required, we could have storage abutting each other with no limit on quantity. This was contrary to the direction that the committee was headed on solid shelving. In 2013, (see Solid Shelving Part 3) the standard was modified to state that if longitudinal flues are not provided in multiple-row racks, (remember they are still not required in multiple-row racking), a transverse flue would be required every 5 feet. A concern was expressed that if the rack were 100 feet deep, this could result in a solid shelf area of 500 square feet (5’x100’), but the general consensus appeared to be that transverse flues allowed for sufficient water penetration. Again, it is not just a solid shelf material that defines solid shelving, it’s the actual pallets of product abutting each other.

Seven years later (this cycle), the committee questioned if this was the right approach and went back to the test from the 70’s and proposed a limit on the depth of a multiple-row rack. The following change has been accepted by the committee and will be finalized in June of 2021, pending outcomes of any potential NFPA membership vote (NITMAM) and NFPA Standards Council action. The new requirement states (my editorial comments are in italics): Multiple-Row Racks

Unless the requirements of or are met, multiple row racks shall be considered racks with solid shelves. Note that you must meet one of the sections.

Multiple-row racks without solid shelves shall be considered open racks where both transverse and longitudinal flues are provided at a maximum of 5 ft. (1.5 m) intervals. Interesting that this provides a solid shelf of 25 square feet, yet for single and double-row racks, we are limited to 20 square feet.

Multiple-row racks shall be considered open racks where transverse flue spaces are provided at maximum 5 ft. (1.5 m) intervals and the rack depth does not exceed 20 ft. (6.1 m) between aisles that are a minimum width of 3.5 ft. (1.1 m). This option eliminates the deep 100 foot rack but provides for a solid shelf area without in-rack sprinklers of 100 square feet. Again for single and double-row racks we are limited to 20 square feet?

This section is stating that either a transverse flue and longitudinal flue is provided every 5 feet or the multiple row rack is a maximum of 20 feet deep and separated by a 3.5 foot aisle from your next multiple row rack or in-rack sprinklers are to be provided under every tier of storage.

FM Global has similar requirements but offers more clarity. Their Data Sheet 8-9, which is available right now, states the following: In multiple-row racks, maintain minimum 6 in. (150 mm) wide vertically aligned longitudinal and transverse flue spaces a maximum of every 5 ft. (1.5 m) throughout the height of the rack. For multiple-row racks not in accordance with Section

a) Provide minimum 6 in. (150 mm) wide transverse flue spaces a maximum of every 5 ft. (1.5 m) horizontally, and

b) Limit the depth of the multiple-row rack, as defined by minimum 8 ft. (2.4 m) wide aisles, to 20 ft. (6 m).

The big differences are that FM is mandating an 8 foot aisle, not the 3.5 feet that NFPA requires. Again, one can treat it as solid shelving and add in-rack sprinklers.

It must be recognized that the in-rack sprinklers are required (if one elects to go this route) even if an ESFR overhead system is provided.

These requirements are proposed for the 2022 edition of NFPA 13 and have already been added to FM Global Data Sheet 8-9. If in-rack sprinklers are not provided in a multiple-row rack, the allowable depth of the rack will be limited or transverse and longitudinal flues will be required. The requirement will more than likely be adopted into the 2022 edition. There is typically a delay in municipalities adopting the latest standard, so you probably will not start to see it enter the overall warehouse environment until at least 2022. FM insureds will have to take it into account immediately.

I have written numerous articles on solid shelving and they can be found on our web site (

As always, I welcome your comments:

  • Jerry Schultz, P.E.

Walmart, Amazon, Lowes, Target and numerous third party logistic (3PL) firms are shifting to pick modules as their warehouse arrangement. A pick module consists of an arrangement of racking with catwalk levels supported from the racking supports on about 10 foot vertical increments so that employees (or robots) can pick the product from a shelf and transport it to the shipping area.

Photo 1: Pick Module Top Level

In the photo above, the “floor” (more properly designated as a catwalk level) of the pick module is supported from the racking shown and the rack system is designed to support the catwalk levels. The photo shows the top level of the racking system, and there can be multiple levels below. This allows for an employee to walk the level and select product from the shelf to transport to the packaging and shipping areas. Most of these installations have conveyors running on the levels so that the product is moved to the packaging and shipping area by itself.

Having provided fire protection engineering and code consulting for numerous pick modules, FPI provides the following for those individuals that are dealing with their first pick module. We believe there are several issues that need to be addressed and understood by all.

  • Occupant load is higher than normally anticipated in a storage occupancy. This will require a careful evaluation of the design strategies for fire alarm, exiting and fire fighter access.

  • The catwalk levels are not to be classified as a story so they do not impact the height and area limitations.

  • Nor do they fall into a floor classification. They do not provide a true separation in that the walking surface is typically a product called Resindek and provides no fire resistance. The module itself is open to the warehouse on the sides.

  • There is typically a lift provided to move products from the ground level to the appropriate upper level. This lift is not an elevator but instead is a vertical reciprocating conveyor. No recall functions are provided and employees are not supposed to be on the lift.

  • Exiting from upper levels is via stairs. The rack designer initially tries to only provide these open stairs within the pick module and take into account vertical travel distance down the stairs to the outside. On all levels, it is important to be aware of any conveyors as traveling around a conveyor will add travel distance. If an exit cannot be reached within the allowable travel distance (which may be as small as 250 feet depending upon the year and interpretation of the code), interior fire rated stair enclosures will be needed.

  • Sprinklers are required on every level. The sprinkler system must be designed to current code, which may include barriers within the shelving units.

  • The shelves will be provided with open face boxes to allow for “picking” the product. If plastic boxes are provided for durability reasons, the sprinkler system design must take this higher hazard material into account.

  • Each client that we have worked with has their own set of fire protection requirements. At the current time, there is no one set of answers.

  • The local official has to be part of the design efforts starting with an initial kick off meeting where the concept of a pick module is explained and fire protection features are discussed. Even though the community is happy to get one of these buildings in their area and it typically provides a nice tax base, the code official has to worry about the fire protection and the life safety of the employees. The input from the official on the front end eliminates the need for critical revisions when the building is trying to get its Certificate of Occupancy. FPI identifies this as “No surprises” and we consider this a fundamental role of the consultant.

  • The fire alarm system and building management system must be carefully coordinated. This is not a typical warehouse occupancy with a limited occupant load, no air conditioning, no or limited conveyors throughout the building, and occupants at grade level, therefore additional life safety considerations must be incorporated into the design. Notification appliances should be provided. The fire alarm system may need to tie into an HVAC system and shut the system down. Conveyors should probably be shut down. Travel distances have to take into vertical distances down the stairs.

As fire protection engineers that have worked on numerous pick modules, The Fire Protection International Consortium, Inc. believes that this sector of the marketplace requires the full involvement of a Fire Protection Engineer as a consultant throughout the entire project. It is the involvement of the fire protection consultant that can ensure that all life safety systems are addressed early on in the project. This will ensure that all design issues are addressed and reviewed by all stakeholders. It will also serve to reduce change orders as a result of plan review comments or surprises at the end of the project when trying to get the Certificate of Occupancy.

It wasn’t one of our projects, but we are aware of a code official requiring additional stairs before he would issue the Certificate of Occupancy because he felt that more were needed. This resulted in a delay in the go live date along with a loss of storage capacity.

Pick module projects require a Fire Protection Engineer to ensure NO SURPRISES!

As always, I welcome your comments:

High volume low speed (HVLS) fans are large mechanical fans that are 6 feet or wider and used in commercial and industrial settings. They are used for moving large amounts of air, and are commonly found in warehouses and similar environments. However, the fire protection requirements surrounding these fans are often overlooked or unknown completely. These fans affect the performance of the sprinkler system, and must be installed in such a manner that they meet NFPA 13 Standard for the Installation of Sprinkler Systems and also NFPA 72 National Fire Alarm and Signaling Code.

From the standard and code referenced above comes a set of requirements for the installation of these fans and the fire protection systems around them.

• The fan shall have a diameter that is not greater than 24 feet. • HVLS fans must be centered between four sprinklers, or approximately as close to centered as possible. By centering the fan, a sprinkler’s discharge pattern will not be obstructed by the blades. • There must be a minimum clearance of 3 feet between the deflector and the fan. • HVLS fans must be wired to shut down immediately upon a waterflow signal from the fire alarm system. This one is particularly important. It is necessary that the fans shut down as soon as the waterflow signal sounds. While the fans are still rotating and moving the air, the heat from the fire needed to activate the sprinklers may not reach the sprinklers leading to a delay in response and the fire growing too big for the sprinkler system. The sprinkler discharge pattern would also be affected, and may not put out the fire as effectively if the water is shifting from its intended pattern due to the air movement around the sprinklers.

The Fire Protection International Consortium, Inc. (FPI) is a fire protection firm that has specialized in the storage field and has assisted numerous clients as they strive to improve environmental conditions for their employees. Although it is best to bring FPI in on a project during the planning process, the firm can work with you at any stage.

Oftentimes, HVLS fans are overlooked by design teams as just another part of the warehouse. However, it is important to be aware of the fire protection impacts during any new or renovation project. FPI can recognize these possible conflicts early on and work to prevent what might be major removal and reinstallation in the future. This will ultimately save the client time and money in the long run, as well as ensure the fire protection requirements have been met and the sprinkler system will function as intended.

If you need any assistance with where to install these fans so that the sprinkler system functions as designed, contact FPI at our main number 1-630-985-3106 or email me directly at

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