Maintaining the highest levels of cleanliness and preventing cross-contamination are paramount in the world of controlled environments.
Cleanrooms depend on precise regulation of temperature, humidity, and airborne particles to protect product integrity and process reliability.
A key component in these systems is the cleanroom pass-through box – an essential tool for safely transferring materials in and out without compromising sterility. Understanding cleanroom pass box working principle helps professionals uphold cleanroom standards and ensure compliance with strict industry regulations.
This article explores the:
- Types of cleanroom pass boxes
- Functions of pass boxes in contamination control
- Operational principles that support cleanroom performance
Types of cleanroom pass boxes
Cleanroom pass boxes enable the safe and contamination-free transfer of materials and equipment within and beyond cleanroom environments.
By utilizing hermetically sealed chambers, they minimize exposure to external contaminants, preserving the controlled conditions essential for cleanroom operations.
Available in various configurations, pass boxes are designed to meet diverse operational requirements.
Static (passive) pass boxes
Static pass boxes are a cost-effective solution for material transfer between two cleanroom spaces or for quick transfers where ventilation inside the pass box is not required.
Semi-active pass boxes
Semi-active pass boxes protect clean environments with pressurized air during material transfer. Ideal between cleanrooms and uncontrolled areas, or between two clean zones for added protection. They connect seamlessly to your existing air handling system.
Active pass boxes
Active pass boxes are stand-alone units equipped with built-in HEPA filtration and a fan system that provides directed airflow through the chamber.
Independent of facility HVAC, they are recommended for transfers between cleanrooms or between a cleanroom and non-classified space, helping prevent cross-contamination during material transfer.
Dynamic pass boxes
Designed for transfers between clean and non-cleanroom environments, dynamic pass boxes provide full protection by creating an internal air barrier.
They feature built-in air handling with recirculating airflow, meaning the air is continuously passed through HEPA filtration to ensure it remains clean at all times. This design maintains consistent internal cleanliness and eliminates the need for additional infrastructure.
Title: Cleanroom pass box working principle of static, active and dynamic pass boxes
What are the cleanroom pass box working principles?
Static cleanroom pass box working principle
Static pass boxes with mechanical interlock systems prevent both doors from being opened simultaneously. When one door is open, the other remains locked, ensuring controlled material transfer and minimizing contamination risks.
Pass boxes with an electronic interlock system also have integrated circuits, electromagnetic locks, control panels, and indicator lights.
When one door is open, an indicator light signals its status, and the opposite door remains locked. Once the first door is closed, the indicator on the other side lights up, allowing the second door to be opened. Additionally, for enhanced hygiene control, a UV sterilization system can be integrated.
When one door is open, the other remains locked, ensuring controlled material transfer and reducing contamination risk
Active cleanroom pass box working principle
An active pass box is a stand-alone unit equipped with a built-in fan and H14 HEPA filters that remove 99.99% of airborne particles ≥0.3 μm. The fan directs filtered air into the chamber, creating a constant airflow that helps prevent cross-contamination during material transfer. Unlike semi-active models, active pass boxes do not rely on the facility’s HVAC system, making them highly versatile and suitable for use between cleanrooms or between a cleanroom and a non-classified space.
The airflow inside the chamber is unidirectional and exhausted directly into the cleanroom through an outlet vent, meaning there is no air recirculation.
This ensures a fresh supply of filtered air during every transfer cycle, maintaining controlled conditions without the complexity of a fully dynamic system.
Semi-active cleanroom pass box working principle
A semi-active pass box operates by drawing filtered air from the cleanroom’s existing HVAC system to maintain positive pressure inside the chamber. It doesn’t have its own fan but includes a built-in HEPA filter (typically H14) that removes 99.97% of airborne particles.
The unit typically features a mechanical or electronic interlock system to ensure that only one door can be opened at a time, minimizing the risk of cross-contamination. Suitable for installations between clean and less controlled spaces, the semi-active pass box enhances protection without requiring a built-in fan system.
Dynamic cleanroom pass box working principle
A dynamic pass box is a fully self-contained system for clean, controlled material transfer, especially between cleanrooms and uncontrolled areas. It uses a built-in fan to draw air through a HEPA filter (typically H13), removing 99.97% of airborne particles.
Since it has its own air handling system, it doesn’t require connection to external HVAC. The filtered air circulates continuously, maintaining uniform airflow and a clean internal environment. For applications requiring surface decontamination, the standard air outlet can be replaced with a high-velocity nozzle, which enhances airflow to effectively dislodge dust from materials before they enter the cleanroom.
Dynamic pass boxes are ideal when no existing infrastructure is available or when items need to remain inside longer.
Keen to learn more?
Here’s a quick summary about the difference between static and active pass boxes.
System-independent cleanroom pass boxes from KleanLabs
We have developed the KleanLabs clean room pass box product line for ISO-14644 or GMP-certified applications, ensuring safe and efficient material transfer. Each unit is manufactured in custom sizes and engineered for easy installation, making them adaptable to various structures, including modular cleanroom systems, drywall, and sandwich panels.
Our pass boxes offer customizable features, including UV sterilization, filtration, and ventilation in the active model for enhanced contamination control. By reducing unnecessary cleanroom entries, they help save energy and costs while maintaining cleanroom integrity.
