The smoke detector I worried because good test results and hope that the promise - is true, I can not yet judge understandably after a few months - without battery change 10 years. I have them with magnetic attachments of ELRO (RMAG2 / 2) at normal white-painted ceilings as mounted on wooden ceilings, and it has been dropped anything yet !! It seems important to me here is that the Aufklebeflächen are quite large and flat.