Reason for removal: Oil is present in the air as droplets, mist and vapour. The oil mist created by the compressor may enter the product and must be removed, even if food grade oil is used. Method of removal: The small particle size of oil mist makes it hard to remove entirely from the air. The best solution is, theoretically, an oil free compressor. Since this is not always possible with existing installations and since oil free compressors may contain residual oil, filtration or cyclonic separation (or both combined) is always necessary. For details see chapter "Selection criteria".