The DualAir Check monitor from Air Liquide, Houston, is designed to protect personnel in confined spaces and other locations where low O2 or elevated CO2 levels may pose a hazard. Unlike air quality monitors that use continuously depleting electrochemical sensor cells, the DualAir model features patented zirconium and NDIR cells that provide stable O2 and CO2 readings even in areas where temperature, barometric pressure, and humidity levels are continually changing. The unit is low-maintenance for “plug-and-forget” operation: The O2 sensor requires no quarterly calibration or annual maintenance, and the monitor automatically adjusts to ambient CO2 levels on a weekly or on-demand basis, if desired. In addition, no zero or span adjustments or expensive maintenance is required. For more information, visit Air Liquide.