Balancing pressure for clean rooms

Article details

Balancing pressure for clean rooms (Cleanroom Pressure Balancing)

It is the process of controlling and adjusting the air pressure within the cleanroom to suit the cleanliness class.

Basically, it controls the pressure of the clean room. Higher than the surrounding area (Positive Pressure)

To prevent dust or contaminants from outside from entering the room.

🔧 Principles of balancing pressure in clean rooms
 1. Positive Pressure
 • Used in rooms that need to control dust or contamination, such as medicine rooms and electronic equipment assembly rooms.
 • The pressure inside the room must be higher than outside. Generally from +10 to +15 Pascale.
 2. Negative Pressure (negative pressure)
 • Used in rooms that control the spread of chemicals or germs, such as chemical storage rooms. Infectious disease patient room
 • The pressure inside the room must be lower than outside, for example -10 to -15 Pascale.
 3. Differential Pressure Control
 • Between rooms of different classes, for example from ISO Class 7 → ISO Class 6.
 • Uses an Airlock door and interlock system to maintain pressure against pressure surges.

⚙️ Components of the Balance system

Elements, duties
AHU + HEPA Filter supplies clean air into the room.
Supply Air Grille, air-inlet point
Return Air Grille / Exhaust pulls air out to control pressure.
Airflow Balancing Damper adjusts the amount of air in/out.
Pressure Sensor detects different pressure levels.
BMS/PLC Control controls and alerts pressure.

📐 How to Balance Pressure
 1. Set the desired pressure.
For example, Room A: +15 Pa, Room B: +10 Pa
 2. Measure Airflow (CFM) of Supply and Return.
 • If Supply > Return → The room has positive pressure.
 • If Return > Supply → the room has negative pressure.
 3. Adjust Damper or Volume Control.
 • To balance the air flow in and out as specified.
 4. Install Pressure Gauge / Sensor at all times.
 • Comes with an alarm system if the pressure goes out of range.
 5. Double check (Commissioning) and make a report.
 • Use a tool to measure differential pressure (Manometer or Differential Pressure Sensor).

🧱 Example of setting pressure (Pascal)

Pressure area (Pa)
ISO Class Room 5 +15
ISO Class Room 6 +10
Changing room +5
Hallway 0
Garbage/chemical room -15