If the room is designed as per the clean room specifications proper pressure measuring instruments must have been installed in the rooms. You have to check the number of air changes you have used to arrive the air. Use instruments like u tube ,anemometer ,and pressure gauges to measure various parameters as per the ASHRAE standards and arrive the va

100 CFM = 10 Pa

as per this u could know the pressure difference u want 2 maintain

inside u r rooms

A possible way do create a pressure drop over 2 rooms is to make the difference by means of a different surface of ductwork:

dp = ½ ρ (v2² - v1²).

Suppose v1 = 3 m/s:

dp = 0,5 * 1,3 (v2² - 3²) = 15 , so v2 = 3,75 m/s

suppose that airvolume (Q) to room 1 equals airvolume to room 2, then:

v1 = Q/A1 (A1 = cross section duct 1) and

v2 = Q/A2

so: (Q/A1): (Q/A2) = 3 : 3,75

Then: A1 = 1,25 A2, or A2 = 0,8 A1

So by varying the ductwork cross section you can vary the room pressures.

Of course you can make the pressure difference also by placing another pressure consuming device into the inlet ductwork and then keep A1 equal to A2.

Another possibility to do this in the outlet ductwork from the rooms