Nest Labs Inc, the maker of smart thermostats that Google Inc acquired for $3.2 billion, called a halt to all sales of its smoke alarms on Thursday after it discovered a possible defect that could cause users to turn it off unintentionally. Nest co-founder and Chief Executive Tony Faddell said that, under a unique set of circumstances the alarms Nest Wave feature, which allows a user to switch off the device with a wave of the hand, could be inadvertently activated. Faddell, one of the creators of Apple Incs iPod, apologized in the blogpost for a problem that was discovered during recent laboratory testing. The fact that it could even potentially happen is extremely important to me and I want to address it immediately. He did not specify that set of circumstances.