What is Clean Room, and How It Works
A clean room is a controlled environment designed to maintain extremely low levels of airborne particles such as dust, microbes, aerosols, and chemical vapors. Clean rooms are widely used in industries where even tiny contaminants can affect product quality or safety, such as pharmaceuticals, semiconductor manufacturing, biotechnology, aerospace, and healthcare. The primary goal of a clean room is to ensure that the air inside meets strict cleanliness standards, typically defined by particle concentration limits according to classifications like ISO 14644.
Clean rooms are classified based on the number and size of particles permitted per cubic meter of air. For example, an ISO Class 5 clean room allows significantly fewer particles than an ISO Class 8 environment. The stricter the classification, the more advanced the filtration and airflow control systems must be. These classifications ensure that processes sensitive to contamination—such as microchip fabrication or sterile drug production—can be carried out reliably.
The core of how a clean room works lies in its HVAC system, which is specifically designed for contamination control. High-Efficiency Particulate Air (HEPA) or Ultra-Low Penetration Air (ULPA) filters are used to remove particles from the air. These filters can capture up to 99.97% (or more) of particles as small as 0.3 microns. Air is continuously circulated through these filters to maintain cleanliness levels.
Airflow patterns play a crucial role in clean room performance. Two main types of airflow are commonly used: laminar (unidirectional) flow and turbulent (non-unidirectional) flow. In laminar flow systems, filtered air moves in a uniform direction—typically from ceiling to floor—sweeping contaminants away from critical areas. In turbulent flow systems, air is mixed to dilute contaminants, which are then removed through return air systems. The choice depends on the required cleanliness level and application.
Pressure control is another key feature of clean rooms. Positive pressure is typically maintained inside the clean room relative to adjacent spaces, preventing contaminated air from entering. In some specialized applications, such as handling hazardous materials, negative pressure may be used to contain contaminants within the room. Airlocks and gowning areas are also implemented to control contamination from personnel entering the space.
Temperature and humidity control are carefully regulated in clean rooms, not only for human comfort but also to maintain process stability. Many manufacturing processes are sensitive to environmental conditions, and even small fluctuations can impact product quality. Therefore, clean room HVAC systems are designed to provide precise control over these parameters.
In addition to engineering controls, operational protocols are critical to clean room performance. Personnel must wear specialized clothing, often called “bunny suits,” to minimize particle generation. Strict procedures for cleaning, material handling, and movement within the room are enforced to maintain cleanliness levels.
To design and optimize clean room performance, engineers often use Computational Fluid Dynamics (CFD). CFD simulations help visualize airflow patterns, particle transport, and contamination risks within the space. With tools like tensorHVAC-Pro, engineers can evaluate filter placement, airflow uniformity, and pressure distribution, ensuring that the clean room meets required standards efficiently and reliably.