Air sorting and/or air screening is applied in sorting and screening machines for sorting and/or screening grain, seeds, and similar materials in order to separate from the materials chaff, husks, shells, empty grains and other light materials which are included in the row material but should not be present in the good product. It is of course important to perform this sorting or screening operation as effectively as possible. This requires a strong air flow but on the other hand the air flow cannot be allowed to rise to any high level because the good grains which shall be included in the good product and comprise the heavier particles of the row material, in that case will also be carried away by the air current. Thus, it is a matter of adjusting very accurately the air flow such that at the most single grains only of the good product are carried away by the air current; then, it is pretty sure that there will be obtained an effective separation of the lighter materials which one want to get rid of although it is achieved at the cost of some loss, though a small one, of good product.
The air flow accordingly must be set accurately and carefully, and it may be necessary to adjust from time to time the setting, initially made, when the sorting or screening machine is operating, and it may also be necessary of course to use different settings for different types of material. This means that the machine when operating requires supervision by a skilled person if one does not want to run the risk of too high a loss of good product or, alternatively, will not be satisfied with an inferior sorting or screening result due to an air flow which is too strong or too light, respectively.