Vacuum inside the validated envelope
In a GMP plant the vacuum source is part of the validated environment, so its cleanliness is a compliance question. An oil-sealed pump introduces an oil-migration and vapour-ingress path that validation cannot accept near product; a dry pump keeps the source inside the envelope. That is why oil-free is the default for drying, transfer and filtration, and why a stable domestic supply matters — fewer supply-driven changes mean fewer re-validation events over a machine's life.
