ISO 8 cleanrooms are controlled environments designed to maintain moderate levels of airborne particles and microbial contamination. These cleanrooms are widely used in industries such as pharmaceuticals, medical devices, electronics, food processing, and cosmetics, where contamination control is critical but not as stringent as in ISO 5 or ISO 6 environments. Maintaining proper HVAC systems and air change rates is crucial to ensure the cleanroom operates within its designated ISO classification while protecting products, processes, and personnel.

The HVAC system in an ISO 8 cleanroom plays a central role in controlling air quality, temperature, humidity, and pressure differentials. A properly designed system ensures a consistent supply of filtered air, minimizes particle accumulation, and supports the cleanroom’s operational requirements. Organizations implementing an ISO 8 Cleanroom must carefully design and maintain HVAC systems to meet both ISO standards and industry-specific regulations. Understanding the air change requirements and filtration strategies is essential for achieving effective contamination control.

Air Change Rates and Their Importance

Air changes per hour (ACH) refer to the number of times the air within a cleanroom is replaced with filtered air in one hour. For ISO 8 cleanrooms, the air change rate typically ranges between 20 to 40 air changes per hour, depending on the application and occupancy. This level of ventilation is sufficient to control particulate matter, reduce airborne microbial loads, and maintain a stable environment for less critical manufacturing processes.

The ACH directly impacts particle removal efficiency, temperature stability, and airflow patterns. Higher air change rates improve air cleanliness by rapidly diluting and removing contaminants, while lower rates may be suitable for areas with minimal personnel movement or low contamination risk. Achieving the appropriate air change rate requires careful calculation based on room volume, occupancy, equipment heat load, and process requirements.

Filtration Systems

HEPA (High-Efficiency Particulate Air) filters are the standard for ISO 8 cleanrooms. These filters remove up to 99.97% of particles 0.3 microns or larger from the air. While ISO 8 cleanrooms allow higher particle concentrations than ISO 5 or ISO 6, HEPA filtration ensures that airborne particulate matter remains within specified limits. In some cases, pre-filters or carbon filters are installed upstream to extend the life of HEPA filters and remove larger contaminants or odors.

The HVAC system must be balanced to maintain consistent airflow through the filters while minimizing bypass or leakage. Proper sealing and regular filter maintenance are critical to ensuring continued performance and compliance with ISO 8 standards. Airflow uniformity helps prevent stagnant zones where particles could accumulate, protecting both personnel and products.

Airflow Patterns

Airflow design is crucial for contaminant control in ISO 8 cleanrooms. While laminar or unidirectional airflow is commonly used in critical areas, ISO 8 cleanrooms often employ mixed airflow systems that provide sufficient ventilation and particulate control without the complexity of high-grade laminar flow. Air is typically supplied through ceiling diffusers and removed via floor or low-wall returns, ensuring that contaminants are carried away from critical zones.

Proper airflow design prevents the buildup of particles near equipment, work surfaces, or personnel. CFD (Computational Fluid Dynamics) modeling can help optimize airflow patterns during cleanroom design, ensuring that supply and return vents are positioned to achieve uniform air distribution.

Pressure Differentials

Maintaining positive pressure in ISO 8 cleanrooms relative to adjacent spaces is essential to prevent contamination ingress. The HVAC system must be designed to sustain consistent pressure differentials between cleanrooms and supporting areas, such as gowning rooms or corridors. Pressure control is often achieved through variable air volume systems, dampers, and airlocks, which help maintain the desired environmental conditions even when doors are opened or personnel move between zones.

Monitoring pressure differentials continuously ensures that the cleanroom operates within its specified parameters. Any deviation can compromise air cleanliness and may require immediate corrective action.

Temperature and Humidity Control

HVAC systems in ISO 8 cleanrooms also regulate temperature and humidity, which are critical for both product quality and personnel comfort. Temperature is typically maintained between 20°C and 24°C, while relative humidity ranges from 30% to 60%. Consistent environmental conditions prevent microbial growth, control static electricity, and ensure reliable manufacturing processes. Sensors and automated control systems allow for precise monitoring and adjustments, supporting compliance and operational stability.

Maintenance and Monitoring

Regular maintenance of HVAC systems, including filter replacement, duct cleaning, and fan inspections, is essential for sustained ISO 8 cleanroom performance. Continuous monitoring of airflow, pressure, temperature, and humidity allows operators to detect deviations early and implement corrective measures. Periodic validation and re-certification help ensure that the cleanroom continues to meet ISO standards over time.

Conclusion

HVAC systems and air change rates are fundamental components of ISO 8 cleanroom operation. Properly designed and maintained systems control particle levels, manage airflow, maintain pressure differentials, and regulate temperature and humidity. By optimizing air change rates, filtration, and airflow patterns, organizations can ensure that ISO 8 cleanrooms provide a reliable and controlled environment for a wide range of industrial applications. Effective HVAC management is key to contamination control, regulatory compliance, and the protection of both products and personnel.