Heat, light, space or thermocouple
Can you see the lines? if you can and suspect a leak then get a spray bottle fill it with water and add about 10 drops of dish washing liquid. Spray the lines and if its leaking you can see the bubbles. Whoever fills your propane tank can tell you more about getting someone to check further. If you are worried about leaks into the house any home fix it store(home depot or lowes) will sell carbon monoxide detectors. since your heat is propane those are an excellent idea anyway.
A staff is a type of rod used for walking or in the case of fantasy, magic. A Rod is a cylindrical stick that can have all sorts of uses.
use the screws and plastic anchors that came with it. filling the holes with a dab of caulk after you take it down only takes a minute, then you wont have to worry about the detector falling on your head. if you are renting, by law there should be one up anyways.
