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In cleanroom engineering, the pass box is a critical device for preventing cross-contamination. As a physical transfer channel connecting clean and non-clean areas, its airtightness, material standards, and interlock stability directly affect the overall cleanliness level. This article outlines the technical specifications, customization options, and installation standards of stainless steel pass boxes for procurement reference.

I. Product Definition and Core Functions

A pass box is an auxiliary device used in cleanrooms for transferring small items between clean areas, or between clean and non-clean areas. Its primary purpose is to reduce the frequency of door openings in cleanrooms and minimize contamination risks through physical isolation.

It operates through a dual-door interlocking mechanism to prevent cross-contamination. Most units are also equipped with a UV sterilization lamp for internal disinfection.

II. Material and Structural Standards

For cleanroom-dedicated pass boxes, material and structural design directly determine durability and cleanliness performance.

1. Cabinet Material
   The standard configuration uses 304 stainless steel. Depending on cleanliness requirements, configurations include:

   • Full stainless steel (internal and external)

   • Powder-coated steel exterior with stainless steel interior
     Stainless steel surfaces must be smooth and polished, free of visible weld marks.

2. Internal Structure
   To comply with GMP standards, the internal chamber should feature rounded corners (R-angle design) to avoid dust accumulation in sharp corners, facilitating cleaning and disinfection while preventing microbial growth.

3. Sealing Performance
   Door sealing should use EVA sealing materials or slot-type gasket strips instead of traditional adhesive-type seals, preventing aging and detachment while ensuring high airtightness.

4. Viewing Window
   Standard configuration includes double-layer tempered glass windows for observing internal items and UV lamp operation.

III. Core Configuration and Technical Parameters

Different cleanroom workshops have varying functional requirements. Below are common technical parameters and customizable options:

• Interlock System

  • Mechanical Interlock: Pure mechanical structure, highly reliable, no electrical circuit required, suitable for explosion-proof areas or simple applications.

  • Electronic Interlock: Integrated circuit with electromagnetic locks and indicator lights to prevent misoperation. Ensures strict “one door open at a time” operation.

• Filtration Efficiency (for dynamic models)
  HEPA filter efficiency: ≥ 99.99% @ 0.3–0.5 μm.

• Air Velocity & Airflow

  • Air Shower Pass Box: Nozzle outlet velocity ≥ 20 m/s to remove dust particles from material surfaces.

  • Laminar Flow Pass Box: Air velocity controlled between 0.38–0.57 m/s to maintain internal laminar cleanliness.

• Sterilization System
  Equipped with UV sterilization lamp and independent control switch. Optional timer function for automatic disinfection.

• Differential Pressure & Noise
  Optional differential pressure gauge for monitoring filter resistance. Operating noise ≤ 65 dB.

IV. Non-Standard Customization Capability

Due to varying wall thicknesses, transfer item sizes, and workshop layouts, standard products may not meet on-site requirements. Manufacturers typically offer:

1. Size Customization

   • Standard example: External size (685×500×590 mm) matching internal size (500×500×500 mm).

   • Non-standard customization: Extended-length pass boxes or floor-standing types according to wall thickness and material size. Long-distance models can be equipped with non-powered roller tables to reduce transfer resistance.

2. Functional Extensions

   • Air Shower Pass Box: Equipped with fan and nozzles for automatic blowing to remove surface particles.

   • Explosion-Proof Pass Box: Includes explosion-proof electrical box, motor, and lighting for chemical or special pharmaceutical workshops.

   • Intercom System: Two-way communication system for coordinating door operation between rooms.

3. Door Opening Direction
   Customizable left-hand, right-hand, or double-door opening according to personnel and material flow direction.

V. Installation and Construction Standards

Pass boxes are wall-embedded installations. Installation precision directly impacts sealing performance.

• Wall Opening Preparation
  The wall opening should generally be 10 mm larger than the external dimensions. The unit is embedded and leveled during installation.

• Sealing and Finishing
  Gaps between the unit and wall should be finished with rounded decorative trim and sealed with silicone to eliminate air leakage points.

• Electrical Wiring
  Electronic interlock models require reserved power supply lines to ensure proper operation of UV lamps and electromagnetic locks.

VI. Application Fields

Stainless steel pass boxes are widely used in environments with strict air cleanliness requirements:

• Biological laboratories: Prevent biological leakage and cross-contamination.

• Pharmaceutical factories / GMP workshops: Comply with GMP standards and separate personnel and material flows.

• Food processing plants: Prevent microbial contamination of finished products.

• Electronics factories / LCD / LED facilities: Prevent dust particles from entering clean production areas and affecting product yield.

VII. Purchasing Recommendations

When requesting a quotation, buyers are advised to clearly specify the following:

1. External and internal dimensions (W × H × D).

2. Interlock type (mechanical or electronic).

3. Requirement for UV lamp, intercom system, or roller conveyor.

4. Wall thickness for installation.

5. Whether third-party test reports are required (e.g., HEPA filter efficiency report).

Conclusion

Selecting the appropriate cleanroom pass box requires comprehensive consideration of material quality, interlock reliability, filtration efficiency, and installation services. It is recommended to consult directly with the manufacturer and provide project drawings to obtain a customized solution tailored to specific working conditions.