To do this, the relative humidity needed to drop from 28 percent to 15 percent. Munters suggested a specially designed Cargocaire HCD-series desiccant dehumidifier. Desiccant dehumidifiers work by directing the room's airflow to the face of a slowly rotating wheel that holds a desiccant, a solid, adsorbent material that attracts and holds water on its surface. Desiccants can hold from 10 to 1,000 percent of their dry weight in water vapor. The process airflow is pulled through corrugated honeycomb openings on the face of the wheel impregnated with desiccant, which captures moisture.
Dehumidified air is released into the working environment.
During the process, the desiccant slowly becomes saturated. A second flow, of reactivation air, is a heated stream concentrated on a small part of the wheel. As this airstream passes, it heats the desiccant to remove the moisture and expel it. Beugnet Grand Travaux of Wasqueghal, France, used the F893 in 1999 on the Pouilly en Auxois section of the A6 highway that runs from Paris to Lyon. The company is currently using the road widening machine to build shoulders on the Ussel to Clermont Ferrand section of the A75 highway west of Lyon.