We have sprinklers in our apartment. I guess I should be happy, as they are a safety device, but they also scare me a bit. Please help assuage my fears.
They are pretty low in some rooms. I stood on the bed and look right at one: brass serrated circle on top with a thin tube of red fluid below that.
In the living room, which has 30-ft.-high ceilings, they are way up there. It is hard to imagine flames ever getting in contact with them to set them off. But there is also an electronic device at the center of the ceiling that has what seem to be sensors on it. I wonder if the two are related.
I know you don’t know the particulars of our building, but your WAGs and knowledge re the following will be helpful:
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So, if I held a lighter up to one of these would it go off, or would bigger heat be required?
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Would that set off every sprinkler in the whole apartment? The whole building?!
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Here’s what scares me: would accidentally knocking the top off of one of these things set it–all of them?!–off?! It’s entirely plausibly that one could, say, while painting the room or something, accidentally come in contact with them.
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Would someone’s pulling the fire alarm set off the sprinklers? How about the smoke detectors in the rooms?
Thanks for your input.
Not sure if the sensor in the room is interconnected to the sprinkler system or not, but I’ll say the likelihood is low. Some occupancies with extremely valuable property use an interconnected system which requires the fusing of a sprinkler head from heat, and a thermal detector closing before water flows in the system. Once the sprinkler head(s) which fused have controlled the fire and lowered ceiling temperature, the system ceases to flow water.
More likely, it is a separate smoke detector or fire alarm system. It may be one which sounds only in your unit, it may sound throughout all units in your building, and may or may not connect to a central monitoring station who would dispatch fire authorities upon receipt of an alarm.
Heat buildup at ceiling level occurs much faster than you’d believe. Test rooms at various fire labs equipped with thermocouples would register ceiling temperatures over 1500°F within 5 minutes when ordinary furnishings were ignited by a simulated dropped cigarette.
Re: your questions-
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Yes. 135°F is the ordinary residential head fusing temperature.
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No. Only the head(s) which actually had temperature sufficient to fuse the link would flow. Hollywood would have you believe differently, but that’s BS. The only time all heads flow is in a dry pipe deluge style system, typically enployed in unheated storage areas with a large volume of combustibles, such as outdoor storage at a lumber yard.
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Yes, you could possibly bash one and cause the link to break, but accidental head damage is usually limited to commercial occupancies when they whacked by a towmotor.
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Pull stations don’t activate water flow systems, they activate a local or centrally monitored alarm system.
The glass bulb with the red liquid is what activates your sprinkler head. The liquid is a chemical that will expand and rupture the bulb given a certain temperature. As the system is already charged, once that bulb breaks, water flows. Here’s a chart of color coding: http://www.day-impex.co.uk/images/bulbgraph.jpg
I don’t know if that chart represents an industry standard, but if so, your system will go off at 155 degrees F.
I could only speculate on the specific answers to your questions, so I’ll wait for someone who knows to come along.
My first job was in a company manufacturing sprinkler systems. Unfortunately it was well over 40 years ago so my memories are a little clouded.
The red fluid as you supposed is what expands with the heat to break its container allowing water to impinge on the brass plate. This gives the spray effect. In our systems the water flowing would start the fire warning bell. Only the sprinkler affected by the heat would operate. I have seen a lighter make a sprinkler operate (it’s a long time ago but I think ours went off at about 160-170F degrees.)
I’m sure much progress has occured since then though, and someone with more knowledge of more modern systems can give more help.
Ok, I see that others have beaten me too it. I’ll post my reminiscences anyway, since it took me so long to type out. 
