Detectors all wired in during a recent loft conversion. Have hoovered any dust out, replaced the back up battery. DH even ‘swapped’ two of the detectors around last night (so that the beeping would be further away from our bedroom), but the ‘swapped’ detector near our bedroom continued the beeping? And we now have six of them sitting in front of us and one is still beeping somewhere, but seems like the beep is moving on to the next detector each time we remove one? Any ideas before my light sleeping husband runs away from home.