Date of MFG 1-31-96...My father-in-law gave us his CO alarm today after having it plugged in for almost a half hour it showed a ready of 195. So I reset the alarm then 15 minutes later it showed a reading of 168. Once again I reset the alarm and in 5 minutes it went off a 3rd time with a reading of 125...I have another CO detector and it never beeped once...I was wondering if there was something wrong with this unit.