10/19/2025
With temperatures declining to the low 40s to high 30s, heat pumps are expected to enter defrost mode, engaging auxiliary heat to maintain warm air circulation. The first few defrost cycles can release an unpleasant odor and trigger smoke detectors. We recommend heat pump and electric heat users to proactively activate their systems, raise the temperature, and initiate auxiliary heat to prevent nighttime disturbances or switch on emergency heat and raise the temperature to bring on auxiliary heat. Operating the system during the day with open doors or windows helps to dissipate the odor. If you have a natural/propane system and have yet to use your heat, you may also experience an unpleasant smell during the first few uses.
