Electronic device processing apparatus including factory interface chamber with environmental controls and a purge control apparatus allowing purge of a chamber filter. The filter purge apparatus includes a chamber filter and a flushing gas supply configured to supply flushing gas to the chamber filter when an access door to the factory interface chamber is open to allow personnel safe servicing access to the factory interface chamber. The supply of flushing gas to the chamber filter minimizes moisture contamination of the chamber filter by factory ambient air when the access door is open thereby allowing rapid resumption of substrate processing after factory interface servicing. Purge control methods and apparatus are described, as are numerous other aspects.