I originally replied to call your manufacturer. Difficult to answer when your question is somewhat vague to make/model. You see dependant upon the model, Scott for example, the psi may be variable.
For example the newest NFPA compliant 4500 Scott, is variable. The mask mounted regulator will flow two different rates depending if you are using it normally or if it is in the vibra-alert stage.
The regulator will flow air in different psi configurations and (stages) directional paths to make the vibra alert alarm. When in normal use (not in a low air situation) the flow is less than when vibra-alerting.
Curious to know why you are looking for the pressures? Do you or someone state they are over breathing the delivered supply? Have they been flow tested?
I have found many who use SCBA have been taught the bare minimum to understand the units actual operation... in this day and age of mandatory required protection that is somewhat sad.