A computing system receives blackbody radiation data from a thermal radiation sensor that is located in a room with a heat source and is directed at the heat source. An operating state of the heat source is determined using the blackbody radiation data. Occupancy data is received for a dwelling that includes the room with the heat source; using this data, an occupancy of the dwelling is determined, including an occupancy for the room. It is determined, using the operating state of the heat source and the occupancy of the dwelling, including the occupancy of the room, whether a heat-source alert condition that includes a first threshold time is met. If so, a heat-source alert is provided. A request of a first type is then received to cancel the heat-source alert. In response, the heat-source alert is canceled and the heat-source alert condition is modified.