A standard format gas analyser complete within an IP54 wall mount enclosure. Measures up to two gases. Single infrared optical beam with total flexibility in cell choice, including 15 different electrochemical cells, zirconia oxygen and paramagnetic cells. Sample pump and flow control are provided with simple push on gas entries. Standard autozero with fresh air, or with a scrubber for low range carbon dioxide. Analogue and alarm outputs are provided.