Series EE85 carbon dioxide (CO2) transmitter is designed for measuring CO2 levels in HVAC applications. The units are available for measuring ranges of 0 to 2,000 ppm and 0 to 5,000 ppm. The compact design allows installation in ventilation channels. Due to a small differential pressure created by a special construction of the sampling head, a small stream from the duct is led to the CO2 sensing cell and back to the duct. The air diffuses into the CO2 sensing through a diaphragm. The closed-loop airstream and the diaphragm protect the CO2 sensing cell from pollution, thereby avoiding pollution-related errors, the company says.