A new guess as to why a sprinkler head suddenly failed last June

LAST JUNE, a sprinkler head in the kitchen downstairs suddenly broke open, flooding the area with water — even though no significant heat was present in the vicinity, let alone an actual fire — as reported in this post. At the time, I speculated that the head had deteriorated over time, until it just failed catastrophically.

Since then, I and others (especially the insurance company, so I hear) have struggled to explain why that particular sprinkler head would have been the one to burst. Below the jump, I discuss a factor that recently occurred to me, which I don’t think has previously been considered.…

The Case of the Missing Hood

As noted here, the Historic Structure Report (2003) pointed out that our kitchen lacks a vent hood above its commercial stoves. Such a hood with exhaust fan is supposed to remove grease, smoke, heat, moisture, and odors. 

Rereading that section recently, it got me to wondering: What would be the predictable impact on the fire sprinkler head of our kitchen’s not having an exhaust hood? 

Well, heat of course rises from the stove. The presence of a hood would channel that heat energy out of the room. In contrast, the lack of a hood means that more heat accumulates at the ceiling — at the level of the sprinkler heads. 

What distinguishes this particular head is that it is located almost directly above the stove. Of all the sprinkler heads in the building, this one has been exposed to the most heat, over time.

Whenever the stove or oven was being actively used for cooking, even though it never got quite hot enough at the ceiling level to break open the sprinkler head’s heat-sensitive stopper, perhaps its stopper was made a bit more brittle. 

Perhaps over time, even the relatively mild heat generated by relighting the pilot lights became enough to shatter the stopper?

(In saying this, I admit that I know almost nothing about sprinkler heads. But the fact that they must be inspected every 5 years, and replaced every 100 years, suggests that they are understood to become less reliable over time. Perhaps the company that does our inspections, Affordable Fire Services, can be asked to enlighten us.)

Implications 

If the above hypothesis happens to be correct, then…

• The only other sprinkler head that is in similar danger is the one that is nearest the stove in the adjoining kitchen. Perhaps it should be replaced sooner rather than later.

• Let’s not wait another 75 years to install an exhaust hood.

What did the 2019 Property Condition Assessment say?

The PCA did not mention the issue of an exhaust hood in our kitchen.