Drying. Particles in the thin layer should be exposed fully to the
airstream. The airstream approaching the sample should be as uniform
as possible in temperature and humidity at a given cross section parallel
to the thin layer so that the air contacts sample particles uniformly. Care
should be exercised to prevent displacement of particles in the thin-layer
holder during a test. This situation may arise in a vertical thin-layer in
which airstream flows horizontally through the product, or in a horizontal
thin-layer in which airstream flows upward through the product. The air
velocity approaching the product should be at least 0.3 m/s.