NFPA 496 classified pressurize question

[scha0786]

i am consulting on existing oil and gas facilities. i have a skid/module that is unclassified. within this unclassified skid is a pressurized unclassified ier room. now adjacent to the whole module is a classified area(class 1 div 2) that has an air lock between them. do i need to maintain +0.1 " wc between the whole modules? the classification sheets usually indicate pressurized areas with a p and a circle around it. this particular module is unclass with the ier pressurized. by code can i just maintain a slight positive in the unclass mod relative to the class mod? like +0.05?

i might try to scan in a diagram

thanks