One reason for false alarms - eight legged creepy crawlies!

Overall, I am satisfied with the smoke detector.
A I have since 8.5 years in operation the other two years, both with the Longlife (Lio) battery.
Now there was the old model an alarm in the morning, about two minutes then it was over. The next morning the same game, but this time only the removal of the battery helped. I thought this will be the battery alarm, is now being expected 8 1/2 years old.
Bought new Longlife, used after dinner at the dining room table - and the family fegts off the table - again continuous alarm. Battery nachgemssen 9.45 V - perfect.
Press smoke detectors in the barrel - well then we screw everything first on. Caution one of the four screws is sealed with glue - remove these with a drill 5.5 mm - Remove screw underneath. So then are the parts there, everything cleaned, plugged the battery to the board .... .... Piiiiip.Piiiip Kruzi ....
Then also opened the photo housing - is very easy ... and there ... I trust my eyes ... very slight cobwebs of some arachnids, as well as what hangs in there a Korn / egg / Pups in front of the photocell.
With a brush cleaned again on the vacuum cleaner kept Photo casing reclosed ... and everything was okay again ... so quiet and peaceful. Test performed everything ok.
Reassembled and mounted.

So now I do not know whether the cause may be in others, compressed air can also smoke detectors in closed well be sufficient. Arachnids itself not seen, definitely not a "normal" spider probably more of a mite.

Perhaps an additional protection of the photo housing here would be quite desirable - has anyone here experience with other producers? I post times a picture of housing Photo - unfortunately you can not see the cobwebs that are extremely fine but it is sufficient for the false alarm.