Author(s): Matt Klaus. Published on March 2, 2015.

ONE OF THE BENEFITS of being an NFPA member is the opportunity to ask NFPA staff technical questions about our standards. Looking back at the more than 4,000 questions that were asked about NFPA 13, Installation of Sprinkler Systems, in 2014, one of the most common themes dealt with sprinkler protection in concealed spaces.

While many of our members were looking for a singular statement to the effect of “yes, all concealed spaces have to be sprinklered,” or “no, concealed spaces do not require sprinklers,” the truth is that the answer is not that black-and-white. Section of NFPA 13 contains 18 different requirements that outline where sprinklers can be omitted from concealed spaces. While it is important that users of the standard can locate these requirements, it is more important to understand the starting point for this discussion and the design features that make the omission of sprinklers from concealed spaces acceptable.

When looking at whether or not to provide protection in a concealed space, users of the standard should start in Section 8.1. This section states that sprinklers shall be provided throughout the building unless the standard provides a specific allowance to omit them. Once this baseline logic has been established, the user can go into subsection to look for allowances to omit sprinklers in concealed spaces. Here, the standard provides more than a dozen arrangements that would allow for the omission of sprinklers. Some common themes embedded in the logic for the omission of sprinklers in subsection are:

Noncombustible or limited combustible construction: The type of construction used will play a large role in ignition and flame propagation. Where concealed spaces are constructed of non- and limited-combustible construction, the chance of ignition and fire spread is greatly reduced.

Occupiable space: The ability to occupy a space and potentially do work in the space would disqualify any “concealed space” from not having sprinkler protection. While there is no definition in NFPA 13 for concealed space, the fact that it can be occupied inherently means it is not functionally “concealed” from day-to-day building operations.

Stored goods: The presence of stored goods, not to be confused with storage discussed in Chapters 12 through 21, is another clear indicator that a concealed space must have sprinklers.

Minimal combustible loading: In addition to the prohibition on storage in unsprinklered concealed spaces, there is also a limitation on combustible materials in general. Non- and limited-combustible concealed spaces with no access are permitted to remain unsprinklered, provided there is limited combustible fuel load. This is intended to permit certain items including, but not limited to, wire sheathing, wire ties, and cable trays with combustible components where acceptable to the authority having jurisdiction.

Access: The amount of access to the concealed space is another potential red flag that should indicate to a designer or plan reviewer that a space may require sprinklers. Small access hatches for maintenance of mechanical equipment may be acceptable, while access that would allow the concealed space to contain storage would not.

These are some of the basic concepts that generated the allowable sprinkler omissions in NFPA 13. For more information and the specific language, visit subsection of the standard at the document information page.

Matt Klaus is principal fire protection engineer at NFPA and staff liaison for NFPA 13, 13R, & 13D.