Ei207 random beeping

[Guest Everything is OK?]

Seems like there are some people here who know answers! My old CO alarm expired back in December, so bought a new one - an Ei207. All was fine (at least I think) for the first three weeks, then on New Year's Eve it beeped, once, in teh middle of the night, and again a few hours later. Nothing more. Same the next night. Two beeps, three or four hours apart, then nothing. 

Nothing for a week, then a week later, same thing. Random beep in the middle of the night. Took batteries out, put batteries in. Hour later, starts giving me a random beep again, but to no pattern. 2 minutes, then 40 seconds, back to a minute... take batteries out. 

Aico website says "regular single beep or irregular beep" implies wiring fault. Also, no green light when I press test/hush, which should be the case according to the manual. Swapped over yesterday. Haven't taken new one out of box yet, and suddenly gives me a random beep whilst still in the box, a day and a half after I bought it home. It isn't even yet connected to the base plate, which is apparently required to complete the circuit (according to the manual). 

I'm going mad. No lights at all. It's always a single beep, not the alarm beep. There is no pattern to it. It always sounds when all gas appliances (the boiler and a hob) are off and cold. Literally the only thing that has changed since this started happening is that I have new neighbours in the flat upstairs. The boiler is 4 years old, and when last serviced didn't even register enough for a warning at the flue test. 

What am I missing? Even if there was very temporarily a minor peak of CO to set the alarm off, surely I should get a light flash and alarm sound, not the fault/battery sound! 

TIA for any help! 

[Tom Sutton]

If the batteries are fitted remove them then check it out. I has happened many times according to this site that the beep is emanating from elsewhere not the detector in question.