Too funny!!! And I’m sure the smoke is from cooking and not the patrons’ weeds!!
That's actually a calculation I've made several times. Including once in a military dining facility where there was a 'stuck' front door.
Took forever to get a real engineer to look at the numbers and the plain proof of a few millibars of vacuum compared to outside air pressure.
Simple changes in the make-up air vents, and all was good.
Cooks can do a lot.
/johnny