Role and Calculation of Air Changes per Hour in Clean Room Area

Clean room is a controlled environment that is designed to maintain low levels of air contaminants such as dust, airborne microbes, aerosol particles, and chemical vapors. These controlled environments are crucial in industries such as pharmaceuticals, biotechnology, electronics, and healthcare, where even a small amount of contamination can result in catastrophic consequences.

The air changes per hour (ACH) is an important parameter that is used to measure the cleanliness of the air in a clean room. It refers to the number of times the entire volume of air in a room is exchanged with fresh, outside air in one hour. The ACH is an essential factor in maintaining the cleanliness and control of airborne particles in a clean room. It directly influences the level of cleanliness and the efficiency of eliminating contamination in the air.

The role of ACH in the clean room area is crucial for several reasons. First and foremost, the ACH determines the level of air filtration and ventilation required to maintain the cleanliness of the room. The higher the ACH, the more air changes occur, resulting in a cleaner environment. This is crucial in industries where stringent cleanliness standards need to be maintained to ensure the quality of products and processes.

Furthermore, the ACH plays a crucial role in controlling the concentration of airborne contaminants in the clean room. By increasing the number of air changes per hour, the level of airborne particles and pollutants is reduced, thereby enhancing the quality of the air and minimizing the risk of contamination. This is particularly significant in environments where the production of sensitive products, such as pharmaceuticals and microelectronics, takes place.

The calculation of ACH in a clean room is based on the volume of the room and the supply and exhaust airflow rates. The formula for calculating ACH is:

ACH = (Q × 60) / V


  • ACH is the air changes per hour, 
  • Q is the airflow rate in cubic feet per minute (CFM), and 
  • V is the volume of the room in cubic feet. 

By using this formula, the required airflow rate can be determined to achieve the desired air changes per hour in the clean room area.

the role and calculation of air changes per hour in a clean room area are crucial in maintaining the cleanliness, control of airborne contaminants, and the overall quality of the environment. By understanding the significance of ACH and accurately calculating the required airflow rates, organizations can ensure the optimal performance and effectiveness of their clean room facilities.

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Resource Person: Ali Saleh Ali

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