Need help with inter-locking 2 exhaust fans with a make-up air unit?

I had to do this for a commercial kitchen exhaust fan a year ago. I had a single pole switch in the kitchen pull in a normally open relay that energized a small sub panel that housed only the fan circuits. The feeder circuit for the sub panel was also on a shunt breaker, so it could be de-energized in the event that the fire alarm system was activated.

gr — You have to decide which one {exhaust fan or "make-up vent"} controls the other. Also, is simple interlocking of starter controls acceptable, or do you need something like a vane or sail switch to prove air flow? it is possible a vane switch may be necessary anyway if the “make-up vent’ is a non-powered, passive or static device. [Make it a profitable opportunity at any rate.]