Question on sensibilté .... and autonomy

Update 12/01/2014
On both devices, the batteries are held within three months.
It's really very very short. Too short.
And of course, it sounds at night every 30 sec.
It's a real problem.
Furthermore, this detector has no conformity certification or marking.
60M has published an article stating that CO detectors 7 of 10 CE are ineffective. I have very big doubts about the reliability of these detectors.