The Trane BAYSENS251A CO2 Wall Mount Sensor is an indoor air-quality sensor designed to monitor carbon dioxide levels in occupied spaces. It measures CO2 concentration and provides a signal to compatible HVAC controls, allowing ventilation equipment to respond to changing occupancy conditions. This wall-mounted sensor is used with compatible Trane commercial HVAC systems, including ai... https://www.partshnc.com/trane-baysens251a-co2-wall-mount-sensor