CTDT2 has a probe in the shape of a so-called venturi tube with two air channels. The CO2 sensor element is mounted in the cover part of the casing and the
temperature sensor element is located inside the probe. The air in the ventilation duct is transported to the CO2 sensor element through one half of the probe and then back to the duct through the other half. The temperature sensor is located inside the probe.

Applications
The carbon dioxide level gives a direct indication of the indoor air quality. This information can be used to control ventilation with high precision and improve the air quality. By increasing the air exchange only when it is necessary, it is possible to minimise energy costs. CTDT2 can for example be used to control ventilation in
residential and office areas.