Obstruction criteria FM DS 02-00

[UFT12]

Hello. I would appreciate if someone could enlighten me about obstruction criteria for storage sprinklers per FM DS 02-00. Table 2.5.4.5.4.1 of Interim revision January 2024, tells that when the obstruction is less than 24", it needs to be checked where the obstruction is located to avoid extra sprinklers underneath. However, there is no indication about how much below the ceiling sprinkler the requirement applies.

For example, take the case of an obstruction of 6". Assume it's unavoidable to install it more than 6" horizontally away from the sprinkler. The table says this is not allowed and I understand that if it is to remain there, sprinklers should be install underneath it. The question is, does this apply to any distance below the ceiling sprinkler? Assume a warehouse of 36 ft high where two small desks for paperwork are in the storage area, no separate ceiling, no separation. There are two typical fluorescent long lamps just above them, say at 7' from FFL with a reflector of 5" width. Do I read the table correctly that sprinklers under the lamp are required if located within the first 6" horozntally from the sprinkler above? I would very much like to say no but how do I justify that? I haven't found anything saying the requirement applies up to a vertical distance blah blah ft.

Any help understanding this appreciated.

 

[TravisMack]

I have always been told that these obstructions ≤24" in width are for when the obstruction is ≤36" from the sprinkler deflector measured vertically. Once you get say 6' down, that is not an issue.

Travis Mack, SET, RME-G,
MEPCad, Inc
AutoSPRINK | AutoSPRINK FAB | AutoSPRINK RVT

 

[UFT12]

Thanks Travis, appreciated. I knew there had to be a limit for that. Strange that FM so meticulous with their standards not giving this vital information.