Sprinklers in Obstructed Construction Also Required Above Sound Panels?

11/19/2020

We are sprinkler protecting a building with all I-Beams (W-type) and they are considered Obstructed Construction. The maximum beam depth is 20-inches. All my deflectors are 20" down from the deck.

The owner now wants to put sound panels in each of the beam pockets which will take up about 85% of the space and will hang level to the finished floor but at least 9-inches up to 19-inches down from the deck because the steel slopes.

Would additional sprinklers be needed above these sound panels?

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4 Comments

Dan Wilder

11/19/2020 08:36:13 am

Interesting.....so here's my opinion

Obstructed construction - 1"-6" below up to 22"
-Sprinklers are 20" down (keeping the 1" deflector clearance)
-The design is in compliance

Panels added within obstructed construction. This may change if the structure is obstructed or unobstructed (you say 85% of the pocket)
-1"-12" below - You still comply with the highest panel being 9" down from the deck

Do the panels constitute a potential ceiling cloud?
-If yes and they don't trap the heat, the obstructed construction will and 1"-6" with max 22" is in compliance
-If yes and they do trap heat, the location 12" down is in compliance
-If no and these are just obstructions, see obstructed construction compliance rules at the top.

Franck

11/19/2020 10:57:10 am

As for Dan - Personal interpretation

Your description looks like a cloud ceiling. But some information is missing, to know if we can omit sprinklers above, such as:
- the maximum cloud ceiling height (should not exceed 20 ft if you want to omit sprinklers above it)
- the response time of the sprinklers that have been installed (should be quick response)
- maximum area of coverage from your sprinklers - refer to table 9.2.7.1 (NFPA 13 Edition 2019), as the maximum area covered by your sprinklers below the cloud ceiling depends on the minimum width dimension of your "clouds" and the opening width between clouds (which is expressed in terms of in. per ft of ceiling height).

Casey Milhorn

11/19/2020 12:43:02 pm

Well the 2 main things to consider are heat collection and spray pattern. If panels are recessed up in beam pockets, then do they really change anything about the situation if they weren't there at all?

Spray pattern - Definitely not, they are above the deflector of the heads.

Heat Collection - Maybe, but I would think it would only assist in heat collection and faster activation. I would think that you would have some cooler air become trapped possibly above the panel with more heat being transferred along the bottom of the panels and beams. I don't see how this could lead to "skipping" of sprinklers during activation. Should only help the process along.

But Dan has it pegged as far progressing through the rules if you had to justify it that way to anyone.

Franck

11/20/2020 09:35:03 am

Heat collection is fine if fire is located below the horizontal panels.
Depending on the size of the panels and the openings between 2 panels, we could have an adverse situation where the fire starts just below an opening (as it may be the case along the wall) and the heat plume is collecting above the panels and travel at the ceiling level without possibility to go down and activate the sprinklers (as the panels will act as a screen, which won't be the case if they were not there).

So yes, the obstruction is not a concern from the description.

But the need to provide sprinklers above the panels might be necessary depending on configuration.
(I really hate these cloud ceiling configurations...).

It is the same in a room with a false ceiling where tiles are missing : for reliability purposes it is normally recommended to replace the tiles as soon as possible, in particular if there is no sprinkler above the false ceiling.
Sprinkler above will activate and then push back the heat plume to the lower level where they will activate the sprinklers below the ceiling.
If no sprinkler above, heat is allowed to accumulate only inside the false ceiling area if the fire starts below the opening. And then the fire will grow before being controlled by lower sprinklers, resulting in more fire, smoke and water damages.

But I have to admit that I work for an insurance company (loss control), so I am always recommending more than sometimes necessary (reliability and probability for having the most adverse situation).

For a new situation, I would be quite strict.

By the way, I hope that the accoustic panels are not combustible or installed in an area where combustible dust or oil deposits may accumulate (otherwise you may have an additional issue).
I have seen these panels once installed in a metal working facility using lubricating oil for the equipment and the panels were fully soaked with oil after a few years...
Flash fire expected at the ceiling level in this configuration.

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