The newly improved CEA 266 wall-mounted CO2 gas analyzer is contained in a water and dust tight NEMA 4X enclosure with digital display readout. Ranges of 0-2000 ppm, 0-5000 ppm and 0-1%, 0-2%, 0-5%, 0-10% and 0-20% are available. The sample gas is continuously drawn into the unit through the built-in air pump. A self-draining water trap and dust filter are also provided. The unit includes 0-5 VDC and 4-20 mA outputs and two user adjustable alarms and contact relays.