Principles of clean room airflow
The clean room adopts the principle of laminar flow (unidirectional flow Laminar flow) or turbulent flow (Swift current turbulent flow, non-unidirectional flow) by using HEPA (High Efficiency Particulate Air filter) or ULPA (Ultra Low Penetration Air Filter) filter, to control airborne particles. Laminar or unidirectional airflow systems direct filtered air in a constant flow downward or horizontally to filters located on the wall near the cleanroom floor, or recirculated through a raised perforated floor. Laminar air flow systems are typically used over 80% of the clean room ceiling to maintain a constant air flow. Stainless steel or other non-shedding materials are used in the construction of laminar air flow filters and hoods to keep unwanted particles from entering the air.
Turbulent, or non-unidirectional air flow uses laminar air flow hoods and non-specific velocity filters to keep the air in the cleanroom in constant motion, though not all in the same direction. The coarse air attempts to capture particles that may be in the air and drive them to the floor where they enter the filter and exit the cleanroom environment.
In some places, a vector clean room will also be added: the air is supplied at the upper corner of the room, and a fan-shaped high-efficiency filter is used, or an ordinary high-efficiency filter is equipped with a fan-shaped air supply port, and a return air port is set at the lower part of the other side. The length ratio is generally between 0.5 and 1. This clean room can also reach Class 5 (Class 100) cleanliness.
