Clean room air changes

Clean Room Air Changes

1. Introduction to Air Changes in Cleanrooms

Air changes per hour (ACH) are a critical metric in Cleanroom design and operation. This value indicates how many times the total volume of air in the cleanroom is replaced within an hour. Depending on the CleanRoom Classification, the required ACH can vary significantly, impacting contamination control.

2. Classification Standards and ACH Requirements

According to ISO 14644-1, cleanrooms are classified based on the maximum allowable particulate concentration. For Class 10, for example, a minimum of 400 ACH is often recommended. This rigorous standard ensures that the environment remains suitable for critical operations, such as Semiconductor manufacturing or sterile pharmaceutical production.

3. Factors Influencing Air Change Rates

Several factors can influence the optimal ACH for a cleanroom. These include the size of the room, the type of operations conducted, and the number of personnel present. Larger rooms or those with more complex processes may require higher ACH to maintain cleanliness, adhering to the specifications set forth in the relevant guidelines.

4. Air Filtration Systems

The effectiveness of air changes is heavily reliant on the filtration systems employed. HEPA filters, which capture 99.97% of particles ≥0.3 micrometers, are commonly used in cleanrooms. Their efficiency, combined with the correct ACH, ensures that the cleanroom environment meets the stringent requirements of various industry standards.

Relevant Standards and Guidelines

• iso 14644-1: Cleanrooms and Associated Controlled Environments – Part 1: Classification of Air Cleanliness

• iso 14644-2: Cleanrooms and Associated Controlled Environments – Part 2: Monitoring to Provide Evidence of Cleanroom Performance Related to Air Cleanliness

• FDA Guidelines: Guidance for Industry - Sterile Drug Products Produced by Aseptic Processing. The FDA specifies air change rates for cleanrooms involved in pharmaceutical manufacturing, underscoring the need for stringent controls in sterile production environments.

• GMP (Good Manufacturing Practice): Regulations that outline the minimum requirements for manufacturing, testing, and quality assurance in pharmaceutical and biotechnology industries, emphasizing the necessity of adequate air changes to prevent contamination.

• CEN EN 12312-2: This standard provides specifications for the performance of cleanrooms and controlled environments, including air change rates necessary for maintaining specified cleanliness levels.

• ISO 14644-3: Cleanrooms and Associated Controlled Environments – Part 3: Test Methods. This standard describes methods for testing the performance of cleanrooms, including airflow measurements and air change rates, ensuring compliance with cleanliness classifications.

How Many Air Changes Per Hour for a Clean Room?

1. Introduction to Air Changes: Air changes per hour (ACH) are crucial for maintaining cleanroom standards. The number of air changes refers to how often the air volume in a room is replaced, impacting contamination control and air quality.

2. Classification Standards: Different cleanroom classifications require varying ACH. For instance, Class 100 Cleanrooms typically need between 200 to 600 ACH, while Class 10 may require around 400 ACH to ensure minimal airborne particles.

3. Factors Influencing ACH: The required ACH can be affected by several factors, including room size, type of operations, and the number of personnel. Larger rooms or intensive processes often necessitate higher air change rates.

The Air Requirements for A Clean Room

Cleanroom Classification

Cleanrooms are classified based on their air cleanliness levels. Standards such as ISO 14644-1 outline specific requirements for particulate concentrations, dictating the necessary air change rates for each class.

Air Quality Standards

To maintain required air quality, cleanrooms must adhere to strict particulate limits. For example, Class 10 allows a maximum of 10 particles ≥0.5 micrometers per cubic meter, necessitating frequent air changes to stay compliant.

Filtration Systems

Effective air filtration systems are essential for achieving cleanroom air requirements. HEPA or ULPA filters remove a high percentage of airborne particles, enhancing air quality and reducing the burden on air change rates.

ISO 14644 Air Change Rate

Overview of ISO 14644

ISO 14644 provides a framework for cleanroom classification and testing. It outlines the necessary air change rates to maintain specific cleanliness levels, ensuring compliance with international standards.

Class-Specific Air Change Rates

Different cleanroom classes have distinct air change requirements. For example, Class 100 typically requires 200-600 ACH, while Class 10 necessitates at least 400 ACH to minimize airborne contamination effectively.

How to Calculate ACPH?

1. Definition of ACPH

Air Changes Per Hour (ACPH) quantify how many times the air volume in a cleanroom is replaced in one hour. This metric is crucial for determining the efficiency of ventilation systems and maintaining appropriate cleanliness levels.

2. Basic Calculation Formula

To calculate ACPH, use the formula: 

This formula helps assess the effectiveness of air distribution in the cleanroom.

3. Example Calculation

For instance, if a cleanroom has a volume of 1,000 cubic feet and an airflow rate of 500 CFM, the ACPH calculation would be: 

This indicates 30 air changes per hour.

The ACPH Limit for ISO

1. Class 1 Requirements: For Class 1 cleanrooms, the recommended ACPH is typically around 500 or higher. This high rate is necessary to maintain the extreme cleanliness required for sensitive processes such as semiconductor manufacturing.

2. Class 10 Requirements: Class 10 cleanrooms generally require at least 400 ACPH. This helps to keep airborne particles to a minimum, ensuring that the environment remains suitable for critical applications where contamination can lead to significant issues.

3. Compliance and Documentation: Facilities must document their ACPH measurements and compliance with ISO 14644 standards. This documentation is crucial for regulatory inspections and ensuring ongoing adherence to cleanliness requirements.