The most basic air handling unit program you can do, is maintaining your security, and having a start signal. The start signal could open dampers, start fans and so on.
If start signal and no errors, start the fans. If any errors occur, stop fans!
Taking it just a bit further, adding a regulator and pressure transmitter, you can start regulating the speed of your fan.
I'll show a simple write sheet
A crude mockup animation could be something like this