Bests & Worsts Reviews from Amazon

This is the third Kidde Nighthawk that we've owned and all have exhibited the same behavior - after a little more than a year they produce a false alarm in the dead of night. How do we know the alarms are false? First, the alarm isn't continuous. The unit sounds long enough to get us out of bed and get our hearts pounding and then stops. Second, the display reads 0 ppm CO. Third, when we check the peak level of CO it is always below the threshold level where CO would be a concern. I have tried replacing the battery even though "LB" is not displayed. The result is the same behavior and frustration a week or two later. Our first two units were the combined CO and explosive gases units which others have noted are problematic. However, we have had the same problem with this unit (CO only). Interestingly, the alarm usually sounds in the summer when we have the AC on, rather than when we are heating the house with natural gas. I'm wondering if others have had this problem.