Abstract: A device for monitoring an underground utility vault environment includes environmental sensors including at least one primary sensor and at least one secondary sensor, a processor for receiving output data from the sensors and for compiling an alarm data packet, and a communications module for transmitting data from the device. The processor determines whether an alarm condition is present based on the output data from the primary sensor(s) and, when an alarm condition is present, compiles an alarm data packet comprising data derived from the primary sensor(s) and secondary sensor(s), and causes the communications module to transmit the alarm data packet. The primary sensor(s) may include a carbon monoxide sensor. The device may include a waterproof housing, a plurality of internal sensors including a gas sensor, and a port for allowing gas exchange between the environment outside the housing and the gas sensor and preventing water ingress.