Air Change Per Hour (ACH): Ensuring Air Purity and Cleanroom Performance
The Importance of Air Changes in Cleanrooms
In cleanroom environments, air purity is crucial for maintaining a contamination-free space. Air changes per hour (ACH) is a key metric used to measure how often the air in a cleanroom is filtered and replaced. Cleanrooms achieve their air purity by passing the air through HEPA (High-Efficiency Particulate Air) and ULPA (Ultra-Low Penetration Air) filters, which remove particles from the air.
The more frequently the air passes through the
HEPA/ULPA filters, the fewer particles remain in the room air, which ensures the required cleanliness levels are maintained. By increasing the air changes, cleanrooms can maintain a higher standard of air quality and cleanliness.
What is Air Change Per Hour (ACH)?
Air change per hour (ACH) refers to the volume of air filtered in a cleanroom in one hour, divided by the room volume.
This measurement determines how many times the air in the room is replaced every hour.
In cleanrooms, the appropriate ACH is determined based on the room’s cleanliness class and the specific requirements of the industry.
Higher ACH rates are typically required in environments where
sterility,
precision, and
safety are critical.
ACH Guidelines for GMP Cleanrooms
For Good Manufacturing Practice (GMP) cleanrooms, ACH is used as a rule of thumb for determining the air change rates needed to maintain required cleanliness levels.
Here are the general ACH guidelines for different GMP cleanroom classifications:
- GMP D rooms: 5-10 ACH
- GMP C rooms: 10-15 ACH
- GMP B rooms with Laminar Air Flow: 20-25 ACH
- GMP A rooms with Laminar Air Flow: 30-35 ACH
These guidelines help ensure that cleanrooms maintain a level of air cleanliness suitable for manufacturing processes, particularly in industries like pharmaceuticals, biotechnology, and food processing, where contamination must be minimized.
Note: It is only a guideline!
ACH Guidelines for Fine Electronics and Dust Control
In industries such as electronics manufacturing where the control of dust is critical, ACH rates are even more stringent.
Below are the recommended ACH rates for cleanrooms in fine electronics and dust-sensitive environments.
As you can see, ISO 5 cleanrooms, which require the highest level of cleanliness, are typically designed with laminar airflow and higher ACH values, ranging from 240 to 360 ACH. This ensures that particles are constantly filtered out, keeping the air clean and free of contamination. In contrast, ISO 9 cleanrooms have lower ACH values, with less stringent air quality requirements.
Note: It is only a guideline!
| ISO 14644-1 | ACH (dust) | Air Flow |
|---|---|---|
| ISO 5 | 240-360 | Laminar |
| ISO 6 | 90-180 | Ceiling - Wall |
| ISO 7 | 30-60 | Ceiling - Wall |
| ISO 8 | 15-25 | Ceiling - Ceiling |
| ISO 9 | 2-4 | Ceiling - Ceiling |
How ACH Impacts Cleanroom Design and Operation
Maintaining the correct ACH rate in a cleanroom is critical for several reasons:
- Particle Removal: Higher ACH rates mean more frequent filtration, reducing the likelihood of contaminants in the air.
- Compliance: Many industries, including pharmaceuticals and electronics, have strict requirements for air cleanliness and ACH, ensuring regulatory compliance.
- Environmental Control: A consistent ACH rate helps to maintain stable environmental conditions (e.g., temperature and humidity), which are essential for maintaining product integrity.
The appropriate ACH also helps balance energy efficiency and air cleanliness, especially when designing high-performance cleanrooms that require higher air exchange rates.
Contact Me for Cleanroom Ventilation and ACH Guidance
Understanding and maintaining the correct air change per hour (ACH) is essential for keeping your cleanroom compliant and operational.
Whether you are setting up a new cleanroom or optimizing the ventilation of an existing one, I can help you navigate ACH requirements, cleanroom design, and ventilation systems to ensure your cleanroom meets the necessary standards.
Contact me today
for guidance on cleanroom ventilation, ACH calculations, and achieving optimal cleanroom conditions.