Abstract: A particle sampling system reads the moisture content of particulates (i.e., wood flakes) travelling through a pneumatically-driven conduit to control the remote drier. A rotatable hood penetrating an opening in the conduit is secured by a suitable mounting flange. When the hood is aimed upstream, facing the particle flow, a captivated sample drops through the apparatus into a special sampling compartment. After a reading the hood is rotated into a position facing downstream. Moisture-reading apparatus transmits light through the sampling window to determine moisture content. Readings may be relayed back to the drier for operating parameter correction. A suitable drive motor activates the hood assembly through a friction drive ring. A valve plate within a special housing may be switched between a closed position, defining the sampling compartment within its enclosure, and an open position, venting the apparatus to atmosphere.