AFAIK-- Excuse my ignorance. But what the heck does this mean? I see it every where and feel 'so outa the loop'.
"Rate of rise"- heat detectors need to see a certain rise in temp with in a few seconds. Say 20 deg in 20 sec.
"Fixed temp"- heats need to reach the desired temp before activating.
And the new ones- 1980 and beyond= are combo if so desired.
HID- (wording escapes me now- sorry)-"The older types of fire alarms relied on copper piping filled with air. The "Heat Sensor" was a bigger copper tube connected to the smaller piping. This whole piping system was pressurized. If there was a fire, the pressure would build up in the pipes and set off the fire alarm system. They were very difficult to trouble shoot if you got a leak. You would have to walk around the whole building with soapy bubble water. You would spray the bubble water onto the copper pipes and look for leaks."
Harold, your correct. these are very good. But. only filled with Ambient air. when heated the air pressure rises closing the ckt. Or pessurizing the solonoid.
Still VERY common in special hazard fire Suppression applications. Where no electrical current would be acceptable..
Flamable storage etc.
