I'm rewiring my security system, which was last done in 1991. I came across the pictured device and have no idea what it is. It looks like a fire sprinkler, but it's in my attic and isn't connected to any pipes, nor does it look like it could be connected to a pipe. The wiring is a rat's nest, so it's impossible for me to really tell where it connects to the panel, but they would a bunch of the separate sensors all together, including this one, so I have no idea what's going on with it.

Any idea what it is?

First picture is one in my attic. Second picture is one in my garage.

Looks like a heat detector.

Heat activated, not smoke. Usually installed in dusty environments or in areas subject to steam to prevent false alarms.

Do those wear out to where I should replace it or are they pretty much good forever?

I am sure if you asked an alarm guy, they would say they need to be replaced.

That disk in the middle has a solder that melts at a certain temperature and once it lets go, it sends it into alarm. Kinda like a fuse blowing.

Not sure you can replace the disk, I think it needs to be replaced at that point.

I don't think there is anything that can actually go bad, unless it gets corroded, or you get a broken wire. They are generally mechanical in nature with metal contacts inside.


You can google how they work.


There are more modern versions that will also measure "rate of rise" that would go into alarm if the temp started rising quickly. That would give more notice.

You would probably need to discuss with an alarm professional as to what is compatible with your system.