A LP leak detector is a hand held device designed to find the actual leak
What you have is an LP or to be more exact Explosive gas detector
They last about 5 years on the average than need replacement.
Also, though we call them LP detectors, and that is what it says on the thing, they are really EXPLOSIVE GAS detectors.. This means several things other than LPO will set 'em off
Methane (Farts)
Alcohol (Including your screwdriver splled on the floor)
Gasoline
Propelents used in many spray cans.
To name but 4
Basicaly any gas that can go BOOM