Instruct: Classify Amazon reviews into positive or negative sentiment
Query: KN-COB-B is crap

We have had three of these units for less than six months. We also have two other CO units that are AC only that we have had for a few years.Just about every week one of these three units beeps very loudly for three or four beeps and then quits. This is very annoying when you are sleeping. It does not continue like it is a real alarm. They are not the soft chirps indicating low batteries. I have replaced all the batteries with new quality batteries instead of the cheap ones that come with the unit. Our regular, more expensive, CO units have never gone off at the same time as these cheap units. Buy the more expensive units.We do not think these are unsafe, just annoying.