A computer that facilitates calibration of an environmental monitoring device is described. In particular, the computer may interact with an electronic device of a user of the environmental monitoring device to calibrate the environmental monitoring device. During the calibration, the computer provides user-interface information associated with a user interface that allows the user to select to select to monitor sound corresponding to an alarm output by a legacy device (such as a smoke detector) that is in an external environment that includes the environmental monitoring device. When the user selects to monitor a legacy device, the computer provides an instruction to the electronic device for the user to activate the legacy device. Then, the computer receives legacy-device information from the environmental monitoring device, specifying whether the legacy device was detected, a type of legacy device identified based on the monitored sound and/or a location of the legacy device.