Cleanroom Design is one of the most complex HVAC projects. Because you have to control
Particles, cleanliness, pressure, temperature, humidity, wind direction, wind speed and safety all go together.
Below is Everything you need to know Before starting to design a cleanroom — a practical design for pharmaceutical factories
Electronics, food, lab, hospital, etc.
🧊 Overview of clean room structure
✅ 1) Class of Cleanroom (ISO / FED STD)
You must first specify what class to use because it determines everything else.
Standards used
• ISO 14644-1 → ISO Class 1 – 9
• FED STD 209E (discontinued but still popular) → Class 1, 10, 100, 1,000, 10,000, 100,000
Examples of real work
Class work is commonly used.
Semiconductor ISO 3–5
Pharmaceutical Filling ISO 5
Mixing / Sampling Room ISO 7
Packing ISO 8
The lower the class = the cleaner the room = requires a higher amount of air.
✅ 2) Number of Air Changes per Hour (ACH) for each Class
ACH is “number of air changes per hour”.
It is the heart of the air supply design.
Frequently used ACH values
Recommended ISO Class ACH
ISO 5 240 – 300 ACH
ISO 6 150 – 240 ACH
ISO 7 60 – 150 ACH
ISO 8 20 – 60 ACH
These values keep the room clean. and removes particles quickly
✅ 3) Air filter system (HEPA / ULPA)
The heart of cleanliness is the filter.
Must know:
• Filtering level:
• HEPA H13 (99.95%)
• HEPA H14 (99.995%)
• ULPA U15–U17
• Installation location:
• Ceiling HEPA
• Terminal HEPA
• FFU (Fan Filter Unit)
Layout Airflow in cleanrooms originates from the HEPA position.
• Laminar (Unidirectional) → ISO 3–5
• Turbulent Mixing → ISO 7–8
🧊 Example of Laminar Flow wind
✅ 4) Room pressure (Pressure Cascade)
The cleanroom must have positive pressure to the surrounding area.
To prevent dust and germs
Standard value
• Main chamber (ISO 5, 6): +15–30 Pa
• Secondary chamber (ISO 7, 8): +10–15 Pa
• Hall before entering (Airlock/Ante room): +5 Pa
If the design is wrong → the clean room will leak and lose its condition immediately.
🧊 Pressure Cascade photo
✅ 5) Temperature & Humidity (Temperature & RH Control)
Popular value in the pharmaceutical/electronics industry
• Temp: 20–24°C
• RH: 40–60%
Need to think more:
• Sensible / Latent Load calculation is very high because there is a lot of Fresh Air.
• Must have a Dehumidifier / Reheat Coil to control RH precisely.
✅ 6) Wind direction & wind speed in the room
• Laminar Flow → Velocity 0.3–0.45 m/s.
• Turbulent Mixing → Average velocity near 0.1–0.2 m/s.
The wind direction must “flow from the cleanest point → the dirtiest point.”
❗ 7) Wall, ceiling, and floor materials (Cleanroom Material)
You must know what types of materials the cleanroom uses:
• PU Panel / PIR Panel walls
• Epoxy / Vinyl Seamless floor
• Aluminum ceiling panels
• Food Grade Silicone
Because general materials easily create dust and mold.
❗ 8) Airlock / Gowning Room
It is a system to prevent air leaks before entering the room.
Must design:
• Room pressure
• ACH
• HEPA
• Interlock system (doors do not open at the same time)
❗ 9) Return Air Layout and wind frame position
Depends on the type of work such as
• Medicine room → Low Return (traps dust falling by gravity)
• Electronic Room → High Return
• ISO room 5 → Return both low and high (2-stage removal)
❗ 10) BMS / CPMS / Differential Pressure Monitoring system
A cleanroom must have:
• DPT Sensor in every room
• Temp/RH Monitor
• Alarm when the pressure drops.
• Historical Logging to pass Audit (GMP / )
⭐ Easy to remember summary: You must know this 10 before starting to design a clean room.
1. ISO Class / Required Cleanliness
2. ACH required
3. HEPA/ULPA Filter
4. Pressure Cascade
5. Temp & RH Control
6. Wind direction and wind speed.
7. Room materials
8. Airlock / Gowning Room
9. Return Air Layout
10. Monitoring & Alarm System
