We came out today due to the Carbon/Smoke combo located in the basement area. The combo detector was sounding the low battery alarm. We took the battieres out of the unit and checked the voltage. The batteries volts were high 1.3 volts to low 1.4 volts. The homeowner gave us new batteries for the unit. The new batteries volts were 1.5 volts. We put the new batteries in the combo unit and the alarm stopped. We determined the lower volts in the batteries made the alarm go off. We supplied and installed a new duplex receptacle in the cabinet near the stairs going to the attic due to the existing device showing signs of heat build up. The breaker that controls the device is located in the main panel, bottom right tandem paddle “B”. After installing we tested the device and it is working.