Designing a clean room, an environment with minimal environmental pollutants, is no easy task. It requires careful planning and implementation to establish and maintain a space free from dust, airborne microbes, aerosol particles, and chemical vapors. If you’re embarking on the clean room design journey, here are 10 essential steps to guide you through the process and ensure a successful outcome.
Step 1: Evaluate People/Material Flow Layout Assess the flow of people and materials within the clean room suite. Separate critical processes from personnel access areas to minimize contamination risks. Designate single access points for the most critical spaces to prevent cross-contamination between different processes.
Step 2: Determine Cleanliness Classification Identify the primary clean room classification standard and understand the particulate performance requirements for each cleanliness level. The Institute of Environmental Science and Technology (IEST) Standard 14644-1 provides different cleanliness classifications, along with allowable particle counts at various sizes.
Step 3: Establish Space Pressurization Maintain a positive air pressure within the clean room to prevent contaminants from infiltrating the controlled environment. Research suggests that a pressure differential of 0.03 to 0.05 inches water gauge (w.g.) effectively reduces contaminant infiltration. Higher differentials offer limited benefits.
Step 4: Determine Supply Airflow The required supply airflow in the clean room depends on the cleanliness classification. Refer to the recommended air change rates for each classification. Consider factors such as occupancy rate, particle generation, and space pressurization to determine the appropriate air change rate.
Step 5: Address Air Exfiltration Clean rooms typically operate at a positive pressure, resulting in planned air exfiltration into adjacent spaces with lower static pressure. Additionally, unintended air leakage can occur through outlets, fixtures, and interfaces. Recognize that clean rooms are not entirely sealed and have a small volume leakage rate.
Step 6: Achieve Air Balance Clean rooms experience both planned air exfiltration and unintended air leakage. Understanding the presence of these factors helps achieve proper air balance. Maintain a balanced airflow to prevent excessive pressure differentials that could compromise the cleanliness of the space.
Step 7: Consider Remaining Variables Take into account various factors, such as temperature, humidity, laminarity, electrostatic discharge, and vibration/noise levels. Maintaining suitable worker comfort, controlling electrostatic charges, and minimizing process disruptions are essential for successful clean room design.
Step 8: Design the Mechanical System Layout Develop a mechanical system layout considering factors like space availability, funding, process requirements, cleanliness standards, reliability, energy costs, construction regulations, and climate conditions. Clean room HVAC systems require additional supply air to meet cooling and heating demands.
Step 9: Perform Cooling/Heating Calculations Calculate the heating and cooling requirements for the clean room. Consider climate conditions, filtration, humidification, process loads, and distribution fan heat. Accurate calculations ensure an HVAC system capable of maintaining the desired temperature and humidity levels.
Step 10: Allocate Sufficient Mechanical Room Space As the cleanliness requirements increase, clean rooms demand more mechanical and electrical support. Ensure an adequate allocation of space to accommodate the necessary equipment and infrastructure. The amount of support space varies depending on the clean room’s classification.