Positive Pressure Room

A positive pressure room is a room where the air pressure inside the room is controlled to be higher than the pressure of the surrounding area in order to prevent outside air. (which may be contaminated) into the room, such as an operating room, clean room, or laboratory that requires high cleanliness. Working principle: 1. Sends more air in than air out. The air conditioning system or air supply system sends more air into the room than the air that is exhausted…

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Working principle
1. Sends more air in than air out.
The air conditioning system or air supply system sends more air into the room than the air that is exhausted.
2. Creates positive pressure.
Excess air that isn't vented will force it to escape through leaks or openings, such as doorways.
3. Protects against dust and germs from outside.
Because only air flows out. There is no air flowing in. This prevents dust or germs from outside the room from entering.

Calculation of positive pressure

1. Calculate the air supply rate (Supply Air) and return air/vent air. (Return/Exhaust Air)
Give:
• SA = Supply Air (air supplied in)
• RA/EA = Return Air or Exhaust Air (suction air/exhaust air)
• ΔV = excess air volume = SA - RA/EA

Popular values:
• Typical positive pressure room: SA > RA/EA approximately 10-15%.
• Operating room: Positive pressure approximately +2.5 to +15 Pascale is recommended.

2. Formula for calculating approximate positive pressure.
When the excess air volume ΔV and the leakage area of the room are known, the pressure difference can be estimated from the formula:

ΔP ≈ (ρ/2) × (Q/A)²

where:
• ΔP = pressure difference (Pa)
• ρ = air density ≈ 1.2 kg/m³
• Q = Air leak volume (m³/s) = SA - RA
• A = total leakage area (m²).

Note: This formula is theoretical and may use additional simulation programs for actual design.

Example
Room size 4x4x2.5 m (40 m³)
• Positive pressure +10 Pa is required.
• Air supply = 400 CFM
• Exhaust air = 340 CFM
• Excess wind = 60 CFM (≈ 102 m³/hr).

Result: The room will have a positive pressure of approximately +10-15 Pa if the room leakage is low and there are no permanent openings.

Source catalog reference. Confirm site conditions and the manufacturer’s instructions before applying this information.