Abstract: A vacuum exhaust system and method of evacuating a plurality of chambers is disclosed. The vacuum exhaust system is within a clean room and comprises: a plurality of branch process gas channels each configured to connect to a corresponding chamber and a shared process channel formed from a confluence of the branch channels and configured to provide a shared fluid communication path for process gas from each of the chambers to flow from the clean room to a process channel outside of the clean room. There is also a plurality of branch pumpdown channels each configured to connect to a corresponding chamber and a shared pumpdown channel formed from a confluence of the branch pumpdown channels and configured to provide a fluid communication path for fluid to flow from the clean room to a pumpdown channel outside of the clean room during pumpdown of at least one of the vacuum chambers.