Recently I visited the location of one of our clients. During a normal walk through and discussion about fire safety, the topic of the amount of clearance that is required under sprinkler heads came up. The question was, “the code states that there is to be 18” of clearance away from the sprinkler head. Does this mean then that we can store around the sprinkler head, even horizontally, as long as we maintain the 18” clearance.” Because I knew the wording in this rule can seem a little vague and because I knew there were some exceptions to this rule, I decided to investigate a little more.
photo credit: Zabowski
NFPA 13 contains information about the installation of sprinkler systems. In this formal interpretation, it states that “the clearance between the sprinkler deflector and the top of storage shall be 18” or greater”. This seems fairly straight forward but it does not really address storage horizontally from the sprinkler head. In a further search of the NFPA’s Fire protection Handbook (20thedition), section 16 chapter 11, basically it states the same thing. Knowing that OSHA also has wording on this topic I turned to OSHA 29 CFR 1910.159. This is the section of OSHA that addresses sprinkler systems. They basically state that they have the same requirements that the NFPA has. I did find a very interesting clarification on the subject though. It seems others have had this same question because it has led OSHA to post a clarification letter on their website. Click here to read it. Even though the regulation does not specifically state it, they do interpret the 18” as a “clearance plane”. If you read further though, you will see some exceptions to this concerning storage shelves along a wall.
So really, the simple answer is to not allow any storage to get vertically within 18” of the horizontal plane created by the sprinkler head deflector plate. (However for large-drop and ESFR sprinklers it is 36”). When one really considers what is being attempted here it really does make sense. As a sprinkler head is activated and it sprays out horizontally, it will travel a few feet and start to “fall off”. The basic idea here is to have another sprinkler head spaced accordingly so that as it sprays and “falls off” it is overlapped by the other sprinkler and the area not getting sprayed will not exceed 18” below that “plane”. Seems to make a lot of sense…safety sense.