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  • Jerry Schultz, P.E.

It has been a while since I blogged, so I have a backload of stuff to cover. This one is a reflection on the future (if one can reflect on what is coming). As Bob Dylan sang in 1964:

Come gather 'round people Wherever you roam And admit that the waters Around you have grown And accept it that soon You'll be drenched to the bone. If your time to you Is worth savin' Then you better start swimmin' Or you'll sink like a stone For the times they are a-changin'.

In 1970, Alvin Toffler wrote a book entitled “Future Shock” where he argued that society was undergoing an enormous structural change with an accelerated rate of technological and social change leaving people disconnected and suffering from shattering stress and disorientation, or as he identified it “future shocked.” Just like any other industry, business, or profession, I would argue that the fire protection community is undergoing its own version of future shock, and that we are in the biggest state of change we have ever seen.

If you have followed my blogs, I have spoken about some of these changes, but let’s pause a moment and look at what has happened recently or is about to happen. We, the fire protection industry, are designing buildings, systems and the related fire protection systems for a green environment that we don’t fully understand and in some cases, we are playing catch up.

• Energy storage systems are becoming the norm as we shift to clean energy, but as of today (11/11/2019), we don’t know what the most effective method is to extinguish a lithium ion battery fire once it hits thermal runaway. • We are seeing mass timber facilities being proposed that alter common beliefs about the hazards of combustible materials on high-rise buildings and long-standing fire protection schemes. After the Chicago Fire, we saw buildings shift to brick or other noncombustible elements because of a concern regarding mass conflagrations. Now, high rise buildings are being constructed with wood and the codes are playing catch up. • We are dealing with building facade issues as we see fires starting on the inside, and sometimes outside of the facility and creating spectacular looking fires that sometimes result in fatalities, such as Grenfell but that always result in extensive property damage. Although many of these recent fires can be traced back to lack of proper application of the prevailing codes (and highlight the importance of the NFPA Fire and Life Safety Ecosystem), it begs the question “Have some of our design and installation provisions become overly complex to manage these issues?” • As cars change, we are seeing a fundamental shift from “there has never been a garage fire that has involved more than one car” to multiple floor involvement in a garage. The NFPA Sprinkler System Discharge committee proposed removing automobile parking from an Ordinary Hazard Group 2 occupancy and did not recommend where to place it in the first draft. Related work on this problem is being vetted through the Fire Protection Research Foundation — with the plan being to provide better awareness and guidance related to this evolving hazard. • Flammable gases are being used for the coolant in freezers and refrigerators due to the elimination of chlorofluorocarbons-CFCs.

It is not only the impact of a green environment that is forcing the industry to change, but look at some of the other issues that we are dealing with.

• Concerns have arisen that cardboard boxes have changed, as the box is being given some increase in waterproofing so that it can be left on your front porch. This increased waterproofing changes the way the cardboard behaves in a fire such that the NFPA Sprinkler Committee has proposed classifying cardboard cartons as encapsulated. (This is significant and will be discussed in a later blog). • Testing shows that the survivability time from a fire in your house has significantly dropped due to changes in furnishings. • The industry is concerned about firefighters maintaining communication during an incident, so there is a big push for Distributed Antennae Systems and Bi-Directional Amplification and other methods to improve in building radio communication. • POTS are either gone or about to be gone, and we are now transferring signals via radio or the internet. • School shootings have forced us to consider life safety from a new point of view. (NFPA 3000) • Environmentally friendly foams are being developed and tested given the apparent push to phase out the use of AFFF and FFFP concentrates. • A new antifreeze has been introduced to address the increased combustibility/flammability of previous generation antifreeze concentrates that were used in sprinkler systems. • Sprinkler orifices keep getting larger (k34). • Smart sprinklers are being introduced. • FM is developing criteria for ESFR sprinklers in the rack. • Robots and other forms of building automation are taking over the warehouse workforce. Chet Schirmer (one of the original innovators in the fire protection field and ex chair of the NFPA 13 committee) used to talk about the greatest smoke detector in the building environment being the human nose, and now we are replacing warehouse workers with robots and machines. • NFPA is looking at smart exit signs to create a better response when egress is necessary. • Elevators continue to be pushed for use as another component to aid in the evacuation of high rise buildings (this or course is over 5 years old). • Train fires, involving transportation of crude oil by rail, are being looked at with a recognition that we need some method to extinguish and limit the environmental impact of a non-controlled fire.

All of these issues have either happened in the last 5 years or are evolving now. It is our responsibility to stay current and understand these changes. In my opinion there is a change coming that we are severely underestimating. This change promises to revolutionize the industry, and will force many of us to reconsider our positions on certain long-held safety-related provisions and philosophies. I have told my coworkers that I believe in the next 5 years the design of sprinkler systems will be completely done by the computer with minimal input from a human. By working with BIM, the “designer” will load the building drawings received from the architect via a file uploaded from the cloud, type in the edition of the standard to be used, place any restrictions on equipment (i.e. Schedule 40 pipe for 2” and smaller), input the water supply and the system will be laid out, pipe sizes provided, cut lengths shown, pipe listed all while clearing obstructions. Think about this question: what will you be doing in the next 5 years because I truly believe that much of the design work that relies on human intervention will be gone. Just like my sticky backs, mylar blueprints, hand calculations, and tee square, this field will change.

I have 40 years’ experience in this field and the changes we are seeing now are unprecedented. I went to BrainyQuote ( and looked for a quote about the future and found this one by Walt Disney that summarizes what I am feeling:

Put the blue stuff on the red stuff!

As always, I welcome your comments:

  • Jerry Schultz, P.E.

We have discussed what constitutes solid shelves within a rack structure but it can get a bit confusing when we consider shelf storage itself. NFPA 13 makes a distinction between shelf storage and rack storage. Shelf storage is defined in the standard in Section as:

Storage on structures up to and including 30 in (750 mm) deep and separated by aisles at least 30 in (750 mm) wide.

The standard also acknowledges that it is possible to push shelves together and create Back-to-Back Shelf Storage which is defined in Section as:

Two solid or perforated shelves up to 30 in (750 mm) in depth each, not exceeding a total depth of 60 in (1.5 m) separated by a longitudinal vertical barrier such as plywood, particleboard, sheet metal, or equivalent, with a maximum 0.25 in (6 mm) diameter penetrations and no longitudinal flue space and a maximum storage height of 15 ft (4.6 m).

The definition for a single row rack states that it has no longitudinal flue space and a rack depth up to 6 feet (1.8 m) so the difference between a rack and a shelf is based on the overall dimensions. If a storage aid is less than (or equal to) 30-inches (750 mm) deep, then it shall be considered a shelf. If greater than 30-inches (750 m) and not falling into the back-to-back definition, then it is a rack. It seems pretty clear up to this point, like the expression “I know it when I see it”. Photo 1 is an example of a shelf while Photo 2 is an example of a rack:

Photo 1: Shelf Storage

Photo 2: Rack Storage

The first photo is not more than 30-inches (750 mm) deep and is clearly categorized as a shelf because of its depth, assuming a minimum 30 inch aisle is provided to the next shelf unit. The second photo has dimensions that exceed the 30 inch depth and is designed to accept a much different storage configuration. The shelf storage arrangement is not as substantial as the second photo which is obviously designed for heavier loads. It is worth noting that NFPA 13 does not address the weight that either configuration is expected to support. Up to this point, the distinction is easy to understand and seems pretty straight forward. However, there are some configurations that are not as clear.

Photo 3: Shelf or Rack?

Consider Photo 3 which illustrates two shelves, each around 30-inches (750 mm) wide pushed together which now creates a back to back shelf. The unit is designed to hold a lesser load than what racks can support, but again the problem is that by definition this must be classified as a rack. Let’s look at the definition of shelf storage again — “…not exceeding a total depth of 60-inches (1.5 m) separated by a longitudinal vertical barrier such as…” In this scenario, there is no barrier provided and therefore; it cannot be shelf storage and the only other possible classification for this arrangement would be to call it a rack. It is important to note that since there are no flues present, not only does this fall into a racking classification, but it also becomes classified as (back to the last three blogs) “solid shelving in a rack” and would require sprinklers below every shelf (In the current 2016 edition of NFPA 13, sprinkler protection is required under solid shelving for Class I through IV storage less than 12 feet high or 5 feet high (1.5 m) if a Class A commodity).

One can question NFPA for requiring a vertical barrier within a back to back shelf structure as part of the definition, but one cannot question the wording. If the shelf is wider than 30” (750 mm) and does not have a solid barrier in the middle, then it is a rack. As a rack, one has to evaluate if solid shelving is provided recognizing that as we just went over in the previous three blogs, either the shelving material or the load itself defines the shelf area and determines if solid shelving is present.

Understanding this separation between a rack and a shelf, there is another requirement for shelf storage that has to be understood. Chapter 14 (Class I-IV commodity) and Chapter 15 (Plastic and Rubber Commodity) apply to shelf storage. Both of these Chapters limit the maximum height of shelf storage to 15 feet (4.6 m). If we exceed this height, then we must, once again, treat it as a rack structure.

For years, many occupancies (I came across this in the back room of many department stores) provided shelf storage in their back rooms and would limit the height to 15 ft (4.6 m) or less because this was what could easily be handpicked with rolling ladders. There were several stores that would provide a catwalk level (or multiple catwalk levels) of open grating to allow handpicking at increased elevations. It was common to provide in-rack sprinklers under the grating, consider the area sprinklered and “restart” the maximum height limitation. As an example, place a catwalk level at 10 feet, sprinkler underneath and provide an additional 15 feet (4.6 m) of storage from that point on so that one now had 25 feet (7.6 m) of shelf storage. Basically, the rationale was that by providing sprinklers under the catwalk level, one was raising the floor and could restart the count.

The 2016 edition of NFPA 13 clearly stated that this concept of storage height was not allowed by adding wording to Section which states:

Bin box and shelf storage that is over 12 ft. (3.7 m) but not in excess of the height limits of 14.2.1 and that is provided with walkways at vertical intervals of not over 12 ft. (3.7 m) shall be protected with automatic sprinklers under the walkway(s).

Therefore, one could provide a walkway but still can only go 15 ft. (4.6 m) high. The design scenario discussed above is not allowed. It should be noted that this requirement is not in Chapter 15 yet and it would be worth asking the committee, if I have plastic storage can I exceed the 15 foot (4.6 m) limitation by placing sprinklers under the catwalks?

In summary, a shelf is limited in width to 30 inches (750 mm) or 60 inches (1.5 m) if a vertical longitudinal barrier is provided and it shall be a maximum height of 15 feet. If exceeding these values, one had better look at the rack requirements. When looking at the racking requirements, carefully review the solid shelving requirements because in-rack sprinklers could be required.

As always, I welcome your comments:

  • Jerry Schultz, P.E.

I am back. Sorry for the delay in getting this blog post out, but now let’s talk about what we have to do when we have solid shelving. Up to this point, we have discussed what solid shelving is and spent time talking about how the load can determine if a shelf is a solid shelf. Now we are ready to ask, “So What?” Once we determine that we have solid shelving, what needs to be done?

In the 2016 edition of NFPA 13, Standard for the Installation of Sprinkler Systems, the following Sections apply:

Section Where solid shelving in single-, double-, and multiple-row racks exceeds 20 sq ft (1.9 sq m) in area, but does not exceed 64 sq ft (5.9 sq m), sprinklers shall not be required below every shelf but shall be installed at the ceiling and below shelves at intermediate levels not more than 6 ft. (1.8 m) apart vertically.

Section Where solid shelving in single-, double- and multiple-row racks exceeds 64 sq ft (5.9 sq m) in area or where the levels of storage exceed 6 ft. (1.8 m), sprinklers shall be installed at the ceiling and below each level of shelving.

Let’s take some time to understand this and tie it back to the first two blog posts on solid shelving:

1) If the load exceeds 20 sq ft (1.9 sq m) but is less than 64 sq ft (5.9 sq m), the sprinklers are to be installed at a maximum of 6 foot (1.8 m) vertical spacing. Assume that one is storing doors in boxes laying on the shelf (or the arms of a cantilever rack). The box is 4 feet (1.2 m) by 8 feet (2.4 m) or 32 sq ft (3 sq m). Sprinklers are to be on 6 foot (1.8 m) vertical centers or below every shelf, if the shelves are more than 6 feet (1.8 m) apart.

2) If the load exceeds 64 sq ft (5.9 sq m), then sprinklers are to be below every shelf. Looking back at the earlier example in blog post 1.5 where I discussed cantilever racking and stacked racks, the load is 4 feet (1.2 m) wide by 20 feet (6.1 m) long, or 80 sq ft (7.4 sq m), so sprinklers would be required under each shelf.

The solid shelving requirement has evolved since its first appearance in the standard. In 1999, NFPA 13 incorporated the requirements found in NFPA 231C (Standard for the Protection of Racking) for the first time. At that time the document defined solid shelving as “Solid, slatted, and other types of shelving located with racks that obstruct sprinkler water penetration down through the racks.” The section (7- that outlined what had to be done when solid shelving was present was very basic and stated that sprinklers shall be provided at the ceiling and below every shelf when both the longitudinal and transverse flue were obstructed. Later, the committee felt that this was not specific enough since there was no reference to a minimum distance between flues. AHJ’s were left arguing where flues were required.

In 2002, the requirements were revised to address the issue of flues. The solid shelving definition added requirements that referred to flue spaces. The definition at that time stated:

Solid shelving is fixed in place, slatted, wire mesh, or other type of shelves located within racks. The area of a solid shelf is defined by perimeter aisle or flue space on all four sides. Solid shelves having an area equal to or less than 20 sq ft (1.9 sq m) are defined as open racks. Shelves of wire mesh, slats, or other materials more than 50 percent open and where the flue spaces are maintained are defined as open racks.

There was no reference to the placement of loads in 2002. The reference to the placement of loads that block openings appeared for the first time in the 2010 edition but it did not appear in the definition for Solid Shelving. Instead, a new definition was developed for the Rack Shelf Area which stated: Rack Shelf Area. The area of the horizontal surface of a shelf in a rack defined by perimeter aisle(s) or nominal 6 in. (152 mm) flue spaces on all four sides, or by the placement of loads that block openings that would otherwise serve as the required flue spaces.

Although it seemed evident, even back in 2010, the committee intended to include the loads when determining the rack shelf area, there were issues raised because there was not a clear connection between the definitions and requirements for “Solid Shelving” and the calculation of “Rack Shelf Area”. There was no use of the phrase “rack shelf area” in the solid shelving requirements section. The committee finally added the same requirements within the definition of Solid Shelving in the 2016 edition of the standard. At that time, the committee added the red underlined words below within the Solid Shelving definition.

Shelving that is fixed in place, slatted, wire mesh, or other type of shelves located within racks. The area of a solid shelf is defined by perimeter aisle or flue space on all four sides or by the placement of loads that block openings that would otherwise serve as the required flue spaces. Solid shelves having an area equal to or less than 20 sq ft (1.9 sq m) are defined as open racks. Shelves of wire mesh, slats, or other materials more than 50 percent open and where the flue spaces are maintained are defined as open racks.

In 2002, the committee felt that they had clarified the issue sufficiently but the field interpreted things a bit differently. In the first place, there were officials’ going out and applying the solid shelving requirements to grocery store shelving and requiring sprinklers underneath shelves. The committee dealt with this by adding terms to the definitions for light and ordinary hazard and by running tests on shelving and introducing back to back shelving. The bigger issue is that this new requirement in 2002 did not take into account long standing design criteria. As an example, a longitudinal flue is not required in double row rack up to 25 feet (7.6 m) and is never required in a multiple row rack. Using the load criteria and recognizing that there would be no flue in the double row rack up to 25 feet (7.6 m) and in a multiple row rack of any height, in-rack sprinklers were being mandated in areas that never required sprinklers previously. It took two cycles (2007 and 2010 editions) before the issue was addressed. In the 2013 edition of NFPA 13, the committee added the following in Section (my editorial comments are in italics):

Where multiple-row racks of any height have no longitudinal flue (remember they are not required to have one) or where double-row racks with storage up to and including 25 ft. (7.6 m) in height have no longitudinal flue (again they are not required to have one), the situation shall not be considered solid shelves where transverse flues exist at maximum 5 ft. (1.5 m) intervals and additional in-rack sprinklers shall not be required in accordance with and

By providing a transverse flue on 5 foot (1.5 m) centers, a double row rack up to 25 feet (7.6 m) without a longitudinal flue and a multiple row rack of any depth does not need to be treated as a solid shelf and does not require additional sprinklers.

I do find it interesting that I could have a multiple-row rack that is 100 feet (30.5 m) deep with no longitudinal flue, and as long as I have a transverse flue every 5 feet (1.5 m), this does not constitute a 500 sq ft (46.5 sq m) solid shelf (5x100) and sprinklers are not required by the solid shelving rules. However, if I install a double row rack over 25 feet (7.6 m) tall that is 8 feet (2.4 m), deep without a longitudinal flue, even though I still have a transverse flue every 5 feet (1.5 m), this constitutes a solid shelf of 40 sq ft (3.7 sq m) and sprinklers are to be provided every 6 feet (1.8 m) vertically.

Photo 1: Plan View of Double Row Rack

Photo 2: Plan View of Multiple Row Rack

One other item that occurred in 2016 is that the committee applied the solid shelving requirements to Chapter 13 for the first time. Chapter 13 addresses Miscellaneous and Low Piled Storage. Low piled was defined as storage in 2016 as storage up to 12 feet (3.7 m). The same requirements, including the flue space requirements, apply to storage below 12 feet (3.7 m) when on a rack. In-rack sprinklers are required when solid shelving is present in storage below 12 feet (3.7 m).

In summary, here is where we are as of today:

  • In addition to the shelving material, the load may define the area of the shelf.

  • If the area exceeds 20 sq ft (1.9 sq m), sprinklers shall be provided on 6 foot (1.8 m) vertical centers.

  • If the area exceeds 64 sq ft (5.9 sq m), sprinklers shall be provided below every shelf.

  • If a longitudinal flue is not required, then the solid shelving requirements do not apply if a transverse flue is present every 5 feet (1.5 m).

  • These solid shelving requirements also apply to racks less than 12 feet (3.7 m) high.

  • The requirements have evolved and if under an earlier edition of the standard (pre 2016), bullet points 4 and 5 were not in the document. It is probably necessary to discuss this with the AHJ.

I plan to consolidate the blogs on Solid Shelving into one concise document and offer it as a white paper to those who want it. As I stated back in blog post 1 on solid shelving, this is one of the most misunderstood code requirements out there and requires discussion and review by all impacted.

Next month I plan to talk about shelving and clearly identify the differences between shelving and racking as identified by NFPA 13.

As always, I welcome your comments:

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