I'm planing to build a new laboratory with 2 Fan Filter units 4x4 feet's. I wann have positive pressure system inside like you guys have in one of podcast. Here I'm sending my poor picture how is should look a like. First room is Lab, second is mixing/cooking area for grain spawn and third is like halfway. On picture you can see what are dimensions of all 3 spaces. I don't have a lot od space to build a plenum so I was thinking to just add some fan with filters that will blow air inside of lab but not too strong so I don't get turbulent air in front of my floowhoods. How can I calculate how strong fan I need for that?