In April of 2021 we bought 3 Next Smoke C0 2 detectors. Within 2 months all three had been through 2 sets (6 batteries each) of replacement batteries. At that point, they were removed from service and we've been without for 10 months. During that time I've repeatedly tried to contact customer service only to be unable to request replacement for obviously defective devices. Google couldn't make it harder to request help.