This Guideline deals with procedures for the separation of drops from gases drawing the difference between solid and fluid particles from wet separators (e. g. in cooling towers, evaporation processes or building ventilation) and fluid particles from mist or aerosol separators (drop size order of magnitude ?m). Special importance is given to the subsequent chapter on drop measurement procedures because no standardized drop measurement procedures have existed so far. Practicable measurement procedures are described which are often the basis for guarantee agreements. The current state of the art is documented in a compilation of construction designs and examples of existing drop and mist separators. The Guideline is completed by a chapter on rinsing and scrubbing installations. It is closed by details on the performance guarantees, operation and maintenance of mist eliminators.