The Mark 5 is primarily designed for unattended battery installations, or remote shelters, containing lead acid batteries and charging systems. These batteries emit hydrogen gas when charging. The lower explosive limit for hydrogen in the atmosphere is 4%. The Cerberus I is designed to turn on an exhaust fan if the gas level reaches 1%, and generate an alarm if the concentration reaches 2%. This alarm consists of local 80db horn, a flashing red LED, and a dry contact switch closer for reporting to a remote alarm system. The photoelectric smoke sensor is designed to detect minute combustion products from smoldering wire insulation, battery cases, and other material normally found in these installations. When smoke is detected, a distinctive alarm is emitted from the 80db horn, and a separator dry contact switch reports to the remote alarm system. At this time, the exhaust fan is inhibited in order to deny the fire increased oxygen from outside air. During normal an in the absence of an alarm condition, an internal thermostat will turn on the exhaust fan at a preset temperature to reduce heat build-up in the room. Loss of power to the unit will also generate a dry contact alarm to the remote system. The optional infrared intrusion alarm will trigger a silent dry contact switch closure to the remote system.