The duct mounted Vaisala CARBOCAP® Carbon Dioxide Transmitter Series GMD20 are specially designed for Demand Controlled Ventilation (DCV). The transmitters are easy to install and require no maintenance. The recommended calibration interval is five years.
The GMD20 series transmitters use the silicon-based Vaisala CARBOCAP® sensor. The simple structure and reference measurement capabilities make this single-beam, dual-wavelength NDIR sensor extremely stable and reliable.

The GMD20 series transmitters can be used independently, or incorporated into building energy management systems. Version D has a display. The two sizes in the wall-mount series make them easy to install for most standard junction boxes. The duct units' compact sensor head design requires only a small hole in a ventilation duct, thereby minimizing the risk of leaking gaskets and measurement errors.
In addition to the standard 0 to 20 mA, 4 to 20mA and 0 to 10V outputs, there are three other options: two LonWorks® interfaces and a relay output. The relay output is standard with the display units.