This part of ISO 1608 specifies methods of measuring the volume rate of flow of vapour vacuum Pumps. The Pumps considered comprise the following three classes of oil and mercury vapour Pumps: - diffusion Pumps; - ejector Pumps; - booster Pumps (i.e. Pumps capable of Operation in both the molecular and laminar flow regions, so combining the properties of diffusion and ejector pumps). These Pumps may be with or without baffle(s) or trap(s).