Compounding Cleanroom specifications, such as NAPRA’s various Model Standards for Pharmacy Compounding, clearly specify the pressure differentials that must be maintained between adjoining spaces.

NAPRA’s Model Standards for Pharmacy Compounding of Non-Hazardous Sterile Preparations is a good example.

Non-Hazardous Sterile Compounding Cleanroom Pressure Differentials

  • The pressure differential between the Cleanroom and the Anteroom must be less than or equal 12.5 Pa (0.050 ”WC) and greater than or equal to 5.0 Pa (0.020 “WC).
  • The pressure differential between the Anteroom and the surrounding facility must be less than or equal 12.5 Pa (0.050 ”WC) and greater than or equal to 5.0 Pa (0.020 “WC).
  • In cleanroom applications, differential pressures are typically measured in Pascals (Pa) or Inches Water Column (“WC). Note: 2.5 Pa = 0.010 “WC.

Differential Pressure can be measured with analog differential pressure gauges, digital gauges or sensors that do not include a display.

Monitoring systems like Lavorato Designs Touch Screen systems do not require sensors with a display as the values are displayed on the Touch Screen.

Differential gauges and sensors have two ports marked as High and Low, respectively. The device measures the difference in air pressure between these two ports.

Air tubes are run from the ports on the sensors to the rooms or spaces that need to be compared. The air tubes are connected to each room by plates with air tube fittings usually mounted in the ceiling of the rooms. Multi-conductor cables are used to connect the temperature and relative humidity sensors.


The monitored pressure values are constantly compared to maximum and minimum limits set in the monitoring system. When a value moves outside of the limits, a fault is detected and indicated on the monitoring panel. With Lavorato Design monitoring systems, an audible alarm is raised and the type and location of the fault is clearly indicated on the touch screen. The fault is also recorded on a separate fault logging screen.