An environmental monitoring device that includes a sensor mechanism is described. During operation of the environmental monitoring device, the sensor mechanism provides sensor data based on measurements of environmental conditions in an external environment that includes the environmental monitoring device. Moreover, a control mechanism assesses if the environmental conditions indicate at least one of a set of threats. If yes, the control mechanism provides a corresponding alert. Furthermore, the environmental monitoring device includes a power source with a primary power source and a secondary power source. The secondary power source has at least a 10-year life and may power at least a subset of the functionality of the environmental monitoring device in the event the primary power source fails. For example, the sensor mechanism may include a smoke detector that is powered by the secondary power source in the event the primary power source fails.