The Honeywell Analytics 301EM Series Gas Detection Expansion Module allows the monitoring of toxic and combustible gases and refrigerants. Up to four sensors can be placed 500 ft. away for toxic and combustible gases, and 200 ft. away for refrigerant gas monitoring. The transmitter is equipped with a backlit LCD display and keypad that can be placed in a safe area, remote from the sensors. Alarm relays and Modbus communication are standard. The unit is compatible with the 301C controller.