What Is a Static Pass Box
A static pass box is a sealed chamber designed to transfer materials between cleanrooms or controlled environments without the need for personnel movement. It operates without an active airflow system and relies on two interlocking doors to prevent cross-contamination; one door can only open when the other is securely closed. Inside the box, items are placed and remain in place until the receiving side retrieves them. Because there is no continuous air circulation, the box itself does not actively filter air; instead, it maintains cleanliness by ensuring a physical barrier and following proper transfer protocols.
What Is a Dynamic Pass Box
A dynamic pass box also serves the purpose of transferring materials between clean areas but incorporates an active airflow and filtration mechanism. Unlike its static counterpart, a dynamic pass box contains a HEPA- or ULPA-filtered fan unit that continuously supplies purified air into the chamber. This positive airflow creates a clean environment inside the box, reducing the risk of particulate infiltration from either side. As with static pass boxes, interlocking doors ensure only one door can be opened at a time, but they also benefit from real-time air changes that help maintain cleanliness during material transfers.
Differences Between Static Pass Box and Dynamic Pass Box
1. Airflow and Filtration System
Static pass boxes do not have an internal airflow or filtration system; they rely solely on maintaining a sealed barrier between cleanrooms. In contrast, dynamic pass boxes are equipped with a fan-filter unit that provides continuous, HEPA- or ULPA-filtered air to the chamber, ensuring a clean air environment at all times.
2. Purification Capability
Because static pass boxes lack active filtration, any residual particles inside the chamber remain until manually cleaned. Dynamic pass boxes, however, perform continuous air exchanges through their filtering system, which can significantly reduce particulate levels within the chamber even if the doors are cycled frequently.
3. Pressure Differential Maintenance
Static pass boxes do not maintain a specific pressure differential with adjacent rooms, as they are completely isolated when both doors are closed. Dynamic pass boxes typically maintain a slight positive pressure relative to the surrounding areas, helping to push out any contaminants and prevent infiltration of unfiltered air when doors are opened.
4.UV Light Integration
Static pass boxes often include UV lamps as a disinfection method since they lack active airflow and filtration. The UV light helps reduce microbial load on surfaces during material transfer. On the other hand, dynamic pass boxes typically rely on their continuous HEPA-filtered airflow to maintain cleanliness, making UV lights less common or even unnecessary in many models.
5. Cost
Static pass boxes are generally less expensive to purchase and install because they lack complex fans or filters. Dynamic pass boxes, with their integrated filtration units and additional electrical requirements, incur higher upfront costs as well as ongoing maintenance expenses associated with filter replacements and power consumption.
6. Application Scenarios
Static pass boxes are suitable for transferring non-volatile, low-risk items in environments where strict cleanliness is monitored primarily by room conditions rather than box air changes. Dynamic pass boxes are preferred in higher-grade cleanrooms (such as ISO Class 5 or better) or applications where even minimal particulate contamination could compromise processes, such as semiconductor manufacturing or high-precision pharmaceutical compounding.
Conclusion
In summary, static pass boxes provide a basic, cost-effective solution for transferring items between cleanrooms without active airflow or filtration, while dynamic pass boxes offer enhanced contamination control through continuous, filtered air circulation and slight positive pressure. The choice ultimately depends on required cleanliness levels, budget constraints, and the criticality of contamination control in specific application scenarios.