I'd disagree; the reason we regulate a sprinkler head's proximity to the ceiling is because during a fire condition the heat rises and becomes trapped against the ceiling and continues to accumulate until the heat is great enough to deploy the sprinkler head. If heat is not trapped beneath the ceiling and simply allowed to pass by it the fire conditions that will activate the head will either be a major case of arson or too late in the game to do anything about fire. I'm curious why one was installed here as I don't remember in NFPA 13 requiring a sprinkler head in this location.codeworks said:
To activate the head needs to be in the plume of hot gases and smoke generated by the fire and the smoke plume needs to be hot enough to activate the head. In a still air area the fire plume will rise above the fuel package and spread out as it entrains air--hence the funnel shape smoke cloud over an outdoor fire. The entrained air cools the plume by diluting the hot products of combustion with ambient air. When the plume hits an obstruction like a ceiling it will spread out rolling across the ceiling--this will activate heads around the perimeter of the fire prewetting the surrounding fuel stopping the spread of the fire. Wind can disturb this pattern potentially preventing the upwind side from getting prewetted. Steep sloped ceilings likewise. A hole in the ceiling will draw the smoke and hot gases to it as a chimney draws the smoke into it and entrains air from the room to keep the smoke out of the house. In this case the foot or two of hot gasses traveling along the ceiling stands a good change of activating the head under the hole although not as rapidly as if the hole was not there, unless the fire is directly under this head.tmurray said:
