Not that many E/R vents or doors on the SOLAS equipped ships I’m familiar with, three doors one escape scuttle and IIRC 4 E/R Vents.
The fire doors close automatically each time after someone passes, hook-backs are not allowed. The E/R vents are held open by pneumatic pressure and can be closed either remotely or locally at the vent.
Shutting down the fans and buttoning up the E/R can be done in about the time it takes a crew member to reach the fire control room or where ever the controls are located.