Lilliput,
Yes, air valve volumes were reset (or the remote valves would draw little air with the closer valves wide open), and there are multiple fans (3 at one location, four at the second - one in each group is redundant).
Originally we suggested partial fan shutdown, but the AHJ's...
This just came up on a job of ours. We were aware of the NFPA requirement, but had over 20 - 6 foot hoods. You couldn't open the doors to exit the building with the make-up air AHU's off and the lab fans on. Our were on VFD's so we revised the sequence to slow down the fans in the fire alarm...
