STFC has built new infrastructure to enable particulate control whilst building superconducting radio frequency cavity string and beam line assemblies that can be used in high beta cryomodule applications. The new facility includes an ISO4 cleanroom, low particulate high pressure rinse, and most recently, a nitrogen purge system that can allow varying and controlled purge of nitrogen through vacuum vessels as they are built. The nitrogen purge ensures that particulate ingress onto sensitive surfaces, such as within high beta RF cavities, is minimised. This paper describes the new purge system, its capabilities, and results from thorough validation testing to ensure that it operates within the required specification.