The Valtronics Model 2156 is a non-dispersive infrared gas monitor designed as a fully functional stand-alone unit for the continuous monitoring of carbon dioxide. The optical system is not affected by humidity. The diffusion gas cell is not affected by variations in relative humidity from 0 to 95%. It has a .56" high digital readout and two adjustable level detect circuits with associated front panel indicators (amber and red) and SPDT relay contacts. Uses 120 or 240 VAC.