Clean rooms rely heavily on airflow to maintain their high level of cleanliness. The movement and dispersion of dust particles from people, machinery, and building structures are all influenced by the air currents within the space. To ensure purity, clean rooms use HEPA (High-Efficiency Particulate Air) and ULPA (Ultra-Low Penetration Air) filters, which can capture up to 99.97% to 99.99995% of airborne particles. This filtration process results in highly purified air, allowing cleanrooms to achieve cleanliness levels ranging from 1 to 100 million particles per cubic foot.
However, even with such advanced filtration, dust sources still exist within the cleanroom environment. These include not only human activity but also the operation of machines and the handling of raw materials. If these particles are not properly controlled, they can spread throughout the space, compromising its cleanliness. Therefore, it's essential that any generated dust is quickly removed through the ventilation system and expelled outside.
Airflow speed plays a critical role in maintaining cleanroom performance. Typically, the air velocity is kept between 0.25 and 0.5 meters per second. This range creates a gentle breeze that is easily disturbed by human movement or equipment operation, potentially leading to turbulence. While increasing the airflow speed can help suppress disturbances and maintain cleanliness, it also increases energy consumption and operational costs. Thus, the ideal airflow speed should be determined based on the required cleanliness level to ensure both efficiency and cost-effectiveness.
Maintaining uniform airflow is another key factor in ensuring stable cleanliness. If the airflow is uneven—especially near walls—it can create vortices, making it difficult to achieve and sustain high cleanliness standards. In vertical laminar flow systems, it's crucial that the airspeed remains consistent across the supply surface and the return air grilles. A wind speed of around 0.5 m/s is optimal for uniform airflow, while speeds below 0.2 m/s or above 0.7 m/s can lead to eddies and reduced efficiency. Most cleanrooms operate within the 0.25–0.5 m/s range.
Several factors can influence airflow in a cleanroom, including process equipment, personnel, construction materials, and lighting fixtures. It's important to consider where the airflow may be diverted, especially above production equipment. To prevent contamination, it’s necessary to install an air shower or other pre-filtration system before any potential dust source enters the clean area.
The placement of airflow diversion points on workstations or equipment is also critical. Ideally, these points should be located at two-thirds of the distance between the cleanroom wall and the equipment. This ensures that airflow moves smoothly from the process area to the work zone. If the diversion point is placed too close to the equipment, it can cause improper airflow distribution, leading to dust accumulation in areas where it shouldn't be. This can result in contamination and lower product yield.
Obstructions like work tables can create turbulence at their edges, reducing local cleanliness. Installing return air vents on the table surface can help minimize this issue. Additionally, the choice of materials and the design of equipment play a significant role in preventing airflow from becoming turbulent. Proper planning and layout are essential to maintaining a clean and efficient environment.
ZHEJIANG ERHUI TECHNOLOGY CO.,LTD , https://www.jahhome.com