2.1 Column-Free Structure for Large-Area Negative Pressure Cleanrooms
For negative pressure cleanrooms, columns in the civil engineering or steel structure are the primary source of potential leakage in the enclosure. Although purification color steel plates are used to wrap columns during construction, the side adjacent to the column lacks space for effective sealing. This issue can be mitigated through spatial layout in small negative pressure cleanrooms (e.g., laboratories), but large-area negative pressure workshops-with numerous columns and complex process flows-pose greater challenges for layout adjustments. For such facilities, a grid structure roof (similar to those used in bus/train stations) is recommended during design, creating a large, column-free space. This design not only saves space and improves layout aesthetics but also eliminates leakage risks associated with column wrapping.
2.2 Positive Pressure Source and Negative Pressure Sink
Due to the "black hole effect," tiny particles from the surrounding environment are continuously drawn into the area with the highest absolute negative pressure-undoubtedly the "negative pressure sink." This room is typically the one with the highest toxin level or the greatest risk of virus diffusion.The "positive pressure source" refers to the first room (air lock) at the entrance of the entire negative pressure zone, designed as a positive pressure space with clean air supply and no exhaust or return air. The pressure is controlled between +10Pa and +15Pa. This design allows clean air to seep into the negative pressure zone through door gaps, blocking the path of external contaminated air and preventing viruses in the negative pressure zone from spreading to the outside-functioning like an air lock.
2.3 Enhancing Cleanliness Against Leakage
In negative pressure cleanrooms (especially those with large static pressure differentials), even tiny cracks can significantly affect indoor cleanliness by increasing suspended particles. The enclosure construction of conventional pharmaceutical cleanrooms often has poor airtightness; even high-quality construction can leave numerous tiny gaps, making complete sealing impractical.Instead of investing heavily in improving enclosure airtightness, an alternative approach is to enhance the cleanliness of areas prone to leakage, thereby reducing the number of tiny particles infiltrating the negative pressure zone. The ceiling cavity is the largest potential leakage source in the enclosure. Designing an air conditioning self-purification system in the ceiling area can effectively control the cleanliness of negative pressure cleanrooms.
2.4 Design of Pressure Differential Gradient and Air Change Rate
·The pressure differential gradient should be rationally designed with optimized layout to minimize openings to general areas. The classic biosafety principle of "consistent negative pressure from start to finish" suggests gradually increasing the negative pressure differential from the shoe-changing room to the highest-level negative pressure cleanroom, forming an orderly gradient. Combined with the "positive pressure source" principle (designing the first entrance to the negative pressure zone as positive pressure), this effectively controls cleanliness. While suitable for small negative pressure cleanrooms, this approach may lead to excessively high negative pressure in the highest-level room for large-scale, multi-room negative pressure zones-an undesirable outcome.
·The air change rate should be designed with sufficient redundancy. If cleanliness requirements are not met, increasing both air supply and exhaust volumes (while maintaining the pressure differential gradient) can dilute tiny particles. Negative pressure cleanrooms face issues such as air leakage, high-efficiency filter clogging, and the need for coordinated air supply and exhaust fan units. Given the widespread use of automatic air conditioning control systems, incorporating appropriate redundancy in the air change rate allows adjustments via the control system to meet process requirements.
2.5 Design of High-Efficiency Exhaust Fan Units
Exhaust fan units are the key to achieving negative pressure. Their importance lies not only in exhaust volume but also in the effectiveness of sterilization. For cleanrooms with strict negative pressure requirements, exhaust fan units are usually designed with one in service and one standby. To prevent virus leakage, high-efficiency filters must be installed in exhaust units. According to regulatory requirements, each high-efficiency exhaust outlet must undergo individual leak testing. Therefore, sufficient operational space for leak testing must be considered during design-retrofitting during inspection and acceptance would incur significant costs.
Suzhou Pharma Machinery Co.,Ltd.
2026/02/23
Gino
