“Broken thermostats can release mercury into the air.”
Yeah, if you smash it with a hammer, but why would you?
The mercury is encased in a sealed glass tube, with wire contacts on each end to act as a mechanical switch when the bimetallic spring attached to it responds to the high and low temperature the user sets. Cut in - Cut out. The mercury completes the circuit as it tilts down - you get heating or cooling, and once the temperature desired is achieved, tilts up and shuts off.
I heard many years ago they wanted to ban mercury switches because they could be used as a detonator - put a bomb on a plane, and as it ascended at a certain angle, the mercury would roll across and complete the circuit.
I guess the point I’m trying to make is that such ‘stats are innocuous when used as intended...
No they can't. Liquid Mercury is basically harmless.
Now fluorescent bulbs, on the other hand....