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Thread: Smoke Detector Placement in a Corridor Skylight

  1. #1
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    Smoke Detector Placement in a Corridor Skylight

    I have a renovation project in a hospital where smoke detectors were installed in an Intensive Care Unit in the corridors. The client decided he wanted smoke detectors in any corridor that haa a nursing station in it because this is how all his facilities are designed. To my knowledge this is not required by code. The issue is the corridor ceiling is a flat ceiling with lay in acoustical tiles, in the corridor there are a couple of skylights approximately 6'x6'x7' (WxDxH) in size. These skylights have a peaked top. The inspector is saying the corridor smoke detectors need to be installed at the highest point. However, I don’t see anything in the NFPA 72 (2013) that addresses sky lights. In NFPA 72 (2013) Section 17.7.3.3 this does address the placement of smoke detectors for peaked ceilings, but the overall corridor ceiling is flat and only the small areas of skylight are peaked. Anyone have any experience with this type of application with skylights and smoke detectors in a hospital corridor? Any insight is appreciated.

  2. #2
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    Shujinko:

    If there is no good air flow into the skylights, then a smoke detector at the peak might be a very poor smoke detector location.

    Ordinary air flow in the hall might cause very little flow into the skylight, and a detector in the hall might provide much faster response. Add air leakage to the outside in the skylight, and the location might be the best.

    Back in the early 60s when I was involved with the development of a smoke detector our detector had faster response than competitive units because of the air flow thru our detector, based on tests at UL. Air more readily flowed thru our detector.

    Had the difference been something that we realized at the time of patent application it would have become part of the claims.

    You might be able to run experiments to determine a best location.

    .

  3. #3
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    I would suggest that you review with the inspector what ceiling or ceiling surface definition he / she feels this fits under in Chapter 3 of NFPA 72.

    I would think the overall ceiling wouldn't be considered a "Sloping Peaked-Type Ceiling" just because of some isolated 6'x6'x7' pockets of dead air spaces with no combustibles within them. Can you confirm that there is or is not any sprinkler heads in these pockets? That might help your argument if there are no heads in there.

    If he insists, remember that
    Spot-type smoke detectors shall be located on the ceiling or, if on a sidewall, between the ceiling and 12 in. down from the ceiling to the top of the detector.
    Ron

  4. #4
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    Quote Originally Posted by ron View Post
    I would suggest that you review with the inspector what ceiling or ceiling surface definition he / she feels this fits under in Chapter 3 of NFPA 72.

    I would think the overall ceiling wouldn't be considered a "Sloping Peaked-Type Ceiling" just because of some isolated 6'x6'x7' pockets of dead air spaces with no combustibles within them. Can you confirm that there is or is not any sprinkler heads in these pockets? That might help your argument if there are no heads in there.

    If he insists, remember that
    Spot-type smoke detectors shall be located on the ceiling or, if on a sidewall, between the ceiling and 12 in. down from the ceiling to the top of the detector.
    There is a sprinkler head on the side wall of the sky lights. I guess at this point the only thing to do is look at the definition of a peaked ceiling in chapter 3 and hope the inspector rules in our favor. Also, to add to your smoke detector placement suggestions the smoke detector has to be 36" (horizontally) from the peak of the ceiling.

  5. #5
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    Quote Originally Posted by Shujinko View Post
    There is a sprinkler head on the side wall of the sky lights. I guess at this point the only thing to do is look at the definition of a peaked ceiling in chapter 3 and hope the inspector rules in our favor. Also, to add to your smoke detector placement suggestions the smoke detector has to be 36" (horizontally) from the peak of the ceiling.
    Is it too late to omit the smoke detectors in the corridor? It appears that the hospital is fully sprinklered. Smoke detection is generally not required, although I know the Joint Commission frequently requires stuff above and beyond the code.

  6. #6
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    Quote Originally Posted by gadfly56 View Post
    Is it too late to omit the smoke detectors in the corridor? It appears that the hospital is fully sprinklered. Smoke detection is generally not required, although I know the Joint Commission frequently requires stuff above and beyond the code.
    Yes, it's too late all smoke detectors are installed. And yes we wouldn't have needed smoke detectors since we have a fully sprinkled building. The owner wanted smoke detectors in the corridors since all of his facilities are designed and installed this way. Even though the SD's aren't required by code in this application, they still need to be located in accordance with NFPA 72.

  7. #7
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    Branch Circuit Conduit on Roof Surface

    For a building roof application, where in the code does it say that a branch circuit conduit has to have clearance below it for re-roofing? I thought I saw in code a long time ago that a branch circuit conduit can be mounted on the roof surface but has to have 1' clearance below it (min) for re-roofing purposes. The conduit run would have to be mounted on a 1' pedestal. IS this in the NEC or is this in another code? I can't seem to track down where I found this. Please help!

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    Quote Originally Posted by Shujinko View Post
    Yes, it's too late all smoke detectors are installed. And yes we wouldn't have needed smoke detectors since we have a fully sprinkled building. The owner wanted smoke detectors in the corridors since all of his facilities are designed and installed this way. Even though the SD's aren't required by code in this application, they still need to be located in accordance with NFPA 72.
    Well that is certainly true. The problem is, NFPA 72 doesn't really deal with this sort of thing. Is the skylight constructed with glass walls for its entire depth, or is it more like a light well, with a glass "lid" and maybe 4-6" of vertical glass at the very top and gyp board sidewalls?

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    Quote Originally Posted by gadfly56 View Post
    Well that is certainly true. The problem is, NFPA 72 doesn't really deal with this sort of thing. Is the skylight constructed with glass walls for its entire depth, or is it more like a light well, with a glass "lid" and maybe 4-6" of vertical glass at the very top and gyp board sidewalls?
    It has gyp board side walls to about 5' and then a glass lid that peaks at 7'. I'd say it's more of a light well.

  10. #10
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    Quote Originally Posted by Shujinko View Post
    It has gyp board side walls to about 5' and then a glass lid that peaks at 7'. I'd say it's more of a light well.
    Probably the best you can do is mount a detector on one of the sidewalls as high as possible. Unless the glass lid is set in a mullion frame that lets you mount the detector near the glass surface I don't see any other option.

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