Cleanroom Pass-Through Windows & Pass Boxes — Secure Material Transfer
Personnel movement is the single greatest source of contamination in any cleanroom. Every time a person crosses the cleanroom boundary — gowning, ungowning, re-entering — they introduce a contamination event. Metrolabs cleanroom pass-through windows (pass boxes) eliminate this risk entirely by allowing materials, samples, and supplies to transfer between different cleanliness zones without any person crossing the boundary, without disturbing the pressure differential, and without breaking the sterility of either zone.
Eliminate the Leading Cause of Cleanroom Contamination — Personnel Movement
Every time a gowned person crosses a cleanroom boundary they carry particles from one zone to another. A pass-through box is a sealed transfer chamber built into the wall between zones — allowing materials to move between cleanliness classes while people remain stationary and both zones remain sealed.
Interlocked Doors — No Direct Air Path
The mechanical or electronic interlock ensures only one door can be open at any time. When the outer door is open, the inner door is physically locked — there is never a direct open path between the two zones. This maintains the pressure differential and prevents contaminated air from flowing directly through the transfer chamber from one zone to the other.
Pressure Gradient Preserved
Unlike personnel airlocks where gowning and ungowning can take 5–15 minutes per person — during which the pressure buffer is repeatedly stressed — a pass-through box maintains an airtight sealed cavity between the two zone doors. The HVAC system sees the pass box as an extension of the wall, not a pressure breach.
Active Decontamination in Dynamic Pass Boxes
Dynamic pass boxes go further — an integrated H14 HEPA filter unit provides unidirectional downflow within the pass box cavity during the transfer period, purging any contaminated air that entered with the incoming materials before the clean-side door is released. The result is a micro-ISO Class 5 environment inside the pass box during transfer.
UV-C Surface Sterilisation for High-Risk Transfers
UV pass boxes add a 254nm germicidal UV-C lamp to the cavity — irradiating all exposed surfaces of the transferred items for a timed cycle (minimum 15 minutes, programmed to the PLC) before the clean-side door is released. Critical for transfers into sterile manufacturing zones where surface bioburden of incoming materials is a validated critical control point.
Four Cleanroom Pass Box Configurations
Metrolabs supplies four standard pass-through configurations — each matched to a specific transfer application, contamination risk level, and cleanroom grade:
Static Pass Box — Standard Material Transfer
The most widely specified pass-through configuration for general laboratory and pharmaceutical material transfer. SS 304 or SS 316L body with a sealed, zero-ledge interior, toughened double-glazed view panels, mechanical or electronic door interlock (one-door-open enforced), LED status indicators, and pharmaceutical-grade silicone door gaskets. The static pass box relies solely on door interlock and physical separation — no active air treatment inside the cavity. Available in wall-mounted, frame-mounted, and built-in versions in any custom size from sample-scale to equipment-scale.
Dynamic Pass Box — HEPA-Filtered Active Transfer
The dynamic (or “active”) pass box adds an H14 HEPA filter and fan unit to the static design, creating unidirectional HEPA-filtered downflow inside the transfer cavity during the transfer period. After the outer door is closed, the fan unit runs for a programmable purge cycle — typically 2–5 air changes inside the cavity — before the inner (clean-side) door is released. This achieves an ISO Class 5 (Grade A equivalent) micro-environment inside the pass box for the duration of the transfer, protecting sterile-side products from contamination from the incoming items. Mandatory for transfers into Grade A/B aseptic manufacturing zones.
UV-C Pass Box — Surface Sterilisation Transfer
The UV pass box equips the static or dynamic pass box with one or more 254nm germicidal UV-C lamps that irradiate all exposed surfaces of the transferred items for a timed cycle — minimum 15 minutes, verified by a UV intensity sensor — before the clean-side door is released. UV-C at 254nm is lethal to vegetative bacteria, moulds, and many viruses at appropriate exposure dose. The PLC interlock will not release the clean-side door until the UV cycle completes at the confirmed intensity level. Optional HEPA airflow can be combined with UV-C for a dual-decontamination Dynamic UV pass box. Recommended for BSL-2 and BSL-3 containment labs and pharmaceutical Grade A zones requiring surface bioburden reduction of incoming materials.
Floor-Mounted Pass-Through — Heavy Equipment & Trolleys
A large-format pass-through unit with a floor-level threshold that allows wheeled trolleys, large equipment, autoclave loads, and bulky materials to be transferred between zones without lifting. The floor-mounted design requires careful structural integration with the wall panel system and flooring — all supplied and co-ordinated by Metrolabs as part of the cleanroom construction scope. Available with ramp-free flush floor threshold, integrated floor drain in the transfer cavity, and overhead-clearance HEPA unit for dynamic operation. Full electronic PLC interlock with traffic-light LED indicators on both sides. Used in pharmaceutical production, hospital CSSD, and large-scale manufacturing cleanrooms.
Engineered to the Same Standard as the Wall — Not an Afterthought
A Metrolabs pass-through is not a standard stainless steel cabinet cut into a wall — it is a precision-engineered structural component designed to the same rigorous cleanroom standards as the wall and partition systems that surround it:
SS 304 / SS 316L Body — Electro-Polished Interior
The pass box body, interior walls, shelf, and door frames are fabricated from SS 304 (pharmaceutical grade) or SS 316L (sterile grade, Ra < 0.5 μm EP). The interior is electro-polished to mirror finish — creating a smooth, non-porous surface that can be fully decontaminated by VHP, H₂O₂ vapour, and all standard pharmaceutical disinfectants without surface degradation.
Zero-Ledge Design — Fully Radiused Internal Corners
Every internal corner of the pass box cavity is formed to a minimum R20mm radius — eliminating the sharp 90° angles where dust, particles, and microbial contamination accumulate in standard cabinets. The zero-ledge philosophy extends to the shelf, the door frames, and the junction between the pass box body and the wall panel system.
Mechanical or Electronic Interlock — Dual Options
Mechanical interlock: a direct physical locking rod linkage that prevents Door B from opening while Door A is open — no power required, no electronics to fail. Electronic interlock: PLC-controlled electromagnetic locks with magnetic reed door sensors, LED indicators, configurable dwell time, and 21 CFR Part 11 audit data logging. Both options enforce the one-door-open protocol with equal reliability.
Toughened Double-Glazed Safety Glass View Panel
Both doors carry a toughened or laminated double-glazed safety glass view panel — allowing personnel on either side to confirm the contents of the pass box before opening. The view panel is flush-mounted in the door face, with no particle-trapping rebate. Glass complies with EN 12543 safety glass standards — on breakage, fragments are contained within the door and do not contaminate the pass box cavity or the product.
Medical-Grade Silicone Door Gaskets
Full-perimeter pharmaceutical-grade silicone gaskets on both doors provide an airtight seal when closed, ensuring the pass box cavity maintains its isolation from both zones when both doors are shut. The gaskets are resistant to all standard disinfectants including oxidizing agents, aldehyde-based disinfectants, and alcohols — and can be field-replaced without specialized tools.
Pass-Through Windows Across Every Regulated Cleanroom
Pass boxes eliminate personnel zone crossing wherever materials, samples, or supplies must move between areas of different cleanliness class:
Pharmaceutical Manufacturing
Static and Dynamic pass boxes for raw material, in-process sample, and finished product transfer between GMP grades without personnel crossings.
Aseptic & Sterile Suites
Dynamic HEPA pass boxes for Grade A/B transfer of components, vials, and stoppers — maintaining ISO Class 5 in the transfer cavity throughout.
BSL-2 & BSL-3 Labs
UV-C Dynamic pass boxes for biosecure material transfer — HEPA purge and UV cycle verified by sensor before negative-pressure-side door releases.
Hospital CSSD & OT
Floor-mounted pass-throughs for sterile instrument trolley transfer from sterile processing to operating theatres — without crossing the sterile boundary.
Food & Beverage Production
FSSAI and HACCP-compliant static pass boxes for ingredient, packaging, and sample transfer into high-care food processing cleanrooms.
Biotech & ATMP
Dynamic UV pass boxes for gene therapy, CAR-T, and mRNA manufacturing — double decontamination (HEPA + UV-C) before clean-side release.
Electronics Cleanrooms
Static or dynamic pass boxes for wafer, component, and tool transfer between ISO Class zones — maintaining ISO class at the transfer point.
NABL & Research Labs
Sample and reagent transfer pass boxes for NABL-accredited testing laboratories — preventing cross-contamination between sample preparation and analytical zones.
Long-Term Performance — Custom-Built for Your Workflow
Metrolabs pass-through windows are not off-the-shelf products adapted to fit your cleanroom — they are custom-designed to integrate with your specific wall panel system, your workflow, and your compliance requirements:
Flush Integration with Modular Panel System
Every Metrolabs pass box is custom-fabricated to integrate flush with the surrounding cleanroom wall or door panel system — no protruding edges on either face, no gaps between the pass box frame and the panel that could accumulate contamination or breach the pressure boundary.
Custom Sizing for Your Equipment
Standard pass boxes are designed around your actual transfer items — sample trays, reagent bottles, autoclave bags, equipment components — not around generic catalogue dimensions. Metrolabs designs pass boxes to the exact internal clearances required by your operational workflow.
Airtight Seal Testing at Installation
Every Metrolabs pass box is pressure-tested after installation to verify seal integrity — confirming that the gaskets, the frame-to-wall joint, and the door seals meet the specified air leakage performance. The test result is included in the IQ documentation package.
HEPA and UV System Commissioning
Dynamic and UV pass boxes are commissioned with HEPA filter integrity testing (DOP/PAO test), airflow velocity measurement, and UV intensity sensor calibration — all documented in the IQ record confirming active decontamination system performance before first use.
Pass Box Type Comparison by Application
From Specification to Commissioned Pass-Through System
Metrolabs manages the complete pass-through window supply and installation — from size confirmation through HEPA integrity and UV sensor commissioning:
Size & Type Specification
Pass box type (static/dynamic/UV/floor), internal dimensions, frame material, interlock type, HEPA and UV requirements confirmed. Wall aperture position and size agreed against layout drawings. Custom dimensions for trolley or equipment transfer sized precisely.
Factory Fabrication
Body and doors CNC-fabricated to approved dimensions. Electro-polishing and R20 corner forming completed. HEPA unit and UV-C lamps installed and factory-tested. Interlock wired and function-tested before dispatch.
Wall Integration & Sealing
Pass box fitted flush in wall aperture. Frame-to-panel joint sealed with pharmaceutical-grade silicone. Pressure test performed to verify seal integrity. Electrical connections made to HEPA fan, UV-C lamps, PLC, and LED indicators.
Commissioning & IQ Issue
HEPA filter DOP/PAO integrity test performed and documented. UV-C intensity sensor calibration confirmed. Interlock sequence function-tested. IQ documentation issued including all test results and certificates.
Pass-Through Windows Required by Every Major Cleanroom Regulation
WHO & EU GMP
WHO GMP and EU Annex 1 specify that material transfer between GMP grades must be controlled to prevent cross-contamination. Pass-through boxes with interlocked doors are the primary engineering control for material transfer between Grade A, B, C, and D zones without personnel crossing.
WHO GMP · EU Annex 1ISO 14644 Cleanroom
ISO 14644-4 requires that material transfer systems between cleanrooms of different cleanliness classes maintain the design air cleanliness of each zone — pass-through boxes with interlocked doors and dynamic HEPA airflow satisfy this requirement at the transfer point.
ISO 14644-4BSL Containment
CDC and WHO biosafety guidelines for BSL-2 and BSL-3 facilities specify that material transfer between containment levels must be performed through interlocked pass-through boxes — with active decontamination (HEPA purge or autoclave) for materials leaving the containment boundary.
CDC · WHO BSL GuidelinesFSSAI & HACCP
FSSAI licensing and HACCP critical control point requirements for food manufacturing cleanrooms mandate documented material transfer controls that prevent cross-contamination between high-care and normal zones. Pass-through boxes are the compliant engineering solution at every boundary crossing.
FSSAI · HACCP · FDAReady to Eliminate Contamination-Causing Zone Crossings?
Contact Metrolabs for a free consultation. Our specialists will assess your material transfer points, specify the correct pass box type for each location, and supply and install a custom-built, IQ-documented pass-through system integrated flush with your cleanroom wall panels.
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