Cleanroom Static Pass Box — The Essential Pressure-Seal Gateway Between Clean Areas
A Static Pass Box, also known as a Passive Pass Box, is the primary structural barrier for material transfer between two cleanroom areas of the same ISO class — or from a cleaner zone to a non-sterile zone. Unlike the Dynamic Pass Box, the Static Pass Box operates without an air supply or extraction system. It relies instead on the maintained pressure differential between the two connected rooms and the hermetic integrity of its interlocking seal to prevent any exchange of room air during material transfer.
Passive Pressure-Seal Gateway — Structural Barrier Without Active Air Circulation
A Static Pass Box (also called a Passive Pass Box) is installed between two cleanroom areas to enable material transfer between zones while preventing direct personnel movement between them — maintaining the ISO class integrity of both zones during the transfer event. The key distinction from a Dynamic Pass Box is that the Static Pass Box has no air supply or extraction system — it does not generate its own internal air environment. Instead, it relies on the pressure differential maintained between the two rooms and the hermetic sealing of its interlocking door system to prevent cross-contamination during transfer.
🔒 The Static Pass Box Principle — Pressure Protection Through Hermetic Integrity
In a cleanroom with a maintained pressure cascade — where the Grade A/B production suite is held at a higher pressure than the Grade C/D corridor — the primary risk during material transfer is the momentary air exchange that occurs when a person opens a door or a panel between the two pressure zones. The Static Pass Box eliminates this risk by providing a transfer pathway that never simultaneously connects both zones to open air — the electromagnetic or mechanical interlocking system ensures that only one door can be open at any moment, and the medical-grade silicone gaskets ensure that the closed door provides an airtight seal at the door-to-frame junction. When the transfer is completed correctly — outer door closed, items in chamber, outer door latched, inner door opened — no air from the outer zone ever enters the inner zone. The chamber air (the small volume between the two closed doors) is not drawn into the inner zone during the inner door opening because the inner zone is at higher pressure than the chamber — the air flow during opening is always outward from the clean zone into the chamber, never inward.
Static pass boxes are used across pharmaceutical manufacturing, hospital pharmacy, research laboratories, microbiology labs, food and beverage high-care zones, and any cleanroom environment where the primary contamination risk is personnel movement and door opening between zones — rather than the contamination on the surface of the items being transferred (which is the risk addressed by the Dynamic Pass Box).
How the Static Pass Box Maintains Zone Integrity — Four Engineering Mechanisms
The static pass box achieves contamination control through four engineered mechanisms — not through active filtration, but through structural integrity at every component that could be a pathway for air or particulate exchange between zones.
Electromagnetic Interlocking — The Primary Contamination Prevention Mechanism
The electromagnetic door interlocking system is the most critical engineering feature of the static pass box. A logic PCB monitors the status of both door-position switches (open/closed) and both electromagnetic locks and enforces a single rule: only one door can be open at any time. When Door A is opened, the PCB activates the electromagnetic lock on Door B — Door B cannot be opened until Door A is fully closed and latched, confirmed by the door-position switch. The reverse applies when Door B is opened first. This sequential access rule ensures that the chamber interior is always sealed from at least one of the two zones — so the pressure differential between the two rooms is never exposed to a through-pathway during any transfer event. The PCB is powered from a battery-backed UPS — power loss defaults to both electromagnetic locks engaged, not released. This fail-safe design means that a power interruption during a transfer cycle does not result in both doors becoming openable — the chamber defaults to the most secure state. The optional mechanical door interlocking provides the same sequential access rule through a purely mechanical cam-and-lever mechanism — no electronics required — for facilities where the power supply to the pass box area is not reliable, or where the facility policy requires a non-electrical interlocking system.
Medical-Grade Silicone Gaskets — Airtight Hermetic Door Sealing
The doors of the static pass box seal against medical-grade silicone gaskets — continuous ring gaskets moulded to the door frame perimeter, fabricated from a silicone compound specified for the cleanroom chemical environment: VHP-compatible at 1000 ppm concentration, resistant to IPA and QAC disinfectants at standard cleanroom application concentrations, and non-outgassing (no VOC release into the cleanroom atmosphere). When the door is closed against the gasket, the gasket compresses from its uncompressed height by approximately 25%, forming an airtight seal at the door-to-frame junction — the pressure differential between the two rooms cannot create an air pathway through the gasket at the pressures typically maintained in pharmaceutical cleanroom pressure cascades (10–15 Pa differential). The gasket compression is maintained by the door latch mechanism — the latch pulls the door firmly into the gasket before the electromagnetic lock engages, ensuring the hermetic seal is established before the lock prevents the door from being reopened. Double-glazed toughened safety glass viewing panels are mounted flush with the door frame — the glass panel is sealed to the door frame with the same pharmaceutical-grade silicone at its perimeter, maintaining a zero-ledge glass surface that is as wipeable as the surrounding SS door face.
Aseptic Interior Geometry — Coved Corners for Total Wipe-Down Accessibility
The internal chamber of the static pass box is fabricated from SS 304 or SS 316L with all internal corners coved to a continuous large radius — the floor-to-wall junction, the wall-to-ceiling junction, and all four vertical corner junctions are radiused, eliminating the sharp 90-degree angles where dust particles, moisture, and micro-organisms can settle and become physically protected from the cleaning cloth during wipe-down. A standard right-angle internal corner creates a shadow zone at the base of the angle where the cleaning cloth contacts the two surfaces of the angle but does not reach the vertex — the vertex zone receives the disinfectant spray but not the mechanical wiping action that is required to remove established biofilm. The coved corner eliminates the vertex by replacing the 90-degree junction with a continuous curved surface that the cleaning cloth follows through the corner in a single pass without repositioning. The internal surface is brushed (standard) or mirror-polished (optional) to Ra <0.8μm — a surface smoothness that reduces the microscopic surface features that micro-organisms anchor to, making each wipe-down more effective at removing any organisms that have contacted the surface since the previous cleaning cycle.
UV-C Germicidal Lamp — Automated Surface Sterilisation Between Transfer Cycles
The UV-C germicidal lamp mounted in the upper interior of the static pass box chamber provides surface disinfection of the chamber interior and of any items placed in the chamber during the idle period between transfer cycles — when both doors are closed and interlocked. The UV-C lamp activates automatically after a programmable delay following the closing of the last-opened door, runs for the programmed cycle time (typically 15–60 minutes depending on the transfer frequency and contamination risk profile of the application), and then deactivates automatically. The lamp is interlocked with both doors — UV-C cannot be activated when either door is open (personnel UV-C exposure safety), and both doors are locked during UV-C operation. The UV-C cut-off safety: if either door is opened during an active UV-C cycle (e.g. by forcing the lock during a power interruption), the UV-C lamp is immediately deactivated — this is the UV-C safety logic that protects personnel from UV-C exposure. An optional UV-C hour meter tracks cumulative lamp operating hours, allowing planned lamp replacement at the manufacturer’s recommended life before germicidal output falls below the effective threshold.
Six Engineering Features of the Metrolabs Static Pass Box
Every Metrolabs Static Pass Box is built to these standards — making it a high-performance containment unit rather than a simple wall hatch:
EM / Mechanical Interlocking — Sequential Access, Fail-Safe Logic
Electromagnetic or mechanical door interlocking — configurable at order. The electromagnetic option uses a logic PCB with a battery-backed UPS (power loss defaults to both doors locked). The mechanical option uses a cam-and-lever mechanism entirely independent of electrical power — suitable for facilities where power supply reliability is a concern. Both options enforce the same sequential access rule: only one door open at a time, confirmed by the door-position switch and the LED status indicators. SS-framed doors with double-glazed toughened safety glass vision panels mounted flush with the door frame — zero-ledge, no recessed frame collecting dust. SS 304 or SS 316L handles and hinges.
Medical-Grade Silicone Gaskets — Airtight VHP-Compatible Seal
Continuous ring silicone gaskets on both door frames — moulded to the full perimeter, providing an airtight seal at every point of the door-to-frame junction when the door is closed and latched. Silicone compound specified for VHP compatibility at 1000 ppm, IPA/QAC resistance, and non-outgassing (no VOC release into the cleanroom atmosphere). Gasket compression of approximately 25% when door is latched — sufficient to seal against the 10–15 Pa pressure differential maintained in pharmaceutical cleanroom pressure cascades. Gasket replacement is a routine maintenance task — the gasket is installed in a standard channel in the door frame and can be replaced without disturbing the door mounting or the pass box body.
UV-C Germicidal Lamp — Automated Safety-Interlocked Idle Disinfection
UV-C germicidal lamp mounted in the upper interior of the chamber — covers all chamber surface areas and items placed in the chamber during idle periods. Programmable timer via the control panel (15–60 minutes). UV-C safety cut-off: if either door is opened during an active UV-C cycle, the lamp deactivates immediately — protecting personnel from UV-C exposure. The lamp cannot be activated when either door is open — both doors must be confirmed closed (door-position switch) before the UV-C cycle can start. Optional UV-C hour meter for planned lamp replacement. The UV-C safety logic is a standard feature, not an optional extra.
Coved Interior — 100% Wipe-Down Accessibility, Non-Shedding Surface
The internal chamber is fabricated from SS 304 (standard) or SS 316L (optional) with all internal corners coved to a continuous large radius — eliminating the right-angle junctions where particles and micro-organisms accumulate and become physically protected from cleaning cloth contact. The brushed or mirror-polished internal surface (Ra <0.8μm standard) provides a non-porous, non-shedding surface that resists aggressive disinfectants — IPA, QAC, PAA, chlorine-based solutions, and VHP at standard pharmaceutical concentrations. All internal welds are ground flush and polished — no weld bead features that could collect particles or impede cleaning.
Red / Green LED Status Indicators — Clear Personnel Communication
High-visibility Red/Green LED status indicators are mounted on both door panels — flush with the door face — providing clear visual communication to personnel on both sides of the pass box wall: Green indicates the door is available to open (the opposite door is closed and locked); Red indicates the door is locked by the interlock (the opposite door is open). This dual-sided communication system prevents the most common pass box user error — attempting to open the locked door before the other door has been fully closed — which in mechanical interlocking systems results in the user forcing the lock and damaging the mechanism. The LED indicators make the interlock status immediately readable without any user familiarity with the pass box operating procedure.
Zero-Ledge Flush Mounting — Seamless Modular Panel Integration
Metrolabs Static Pass Boxes are designed to be installed level with the cleanroom panel wall surface on both sides — the door frames are specified to the thickness of the cleanroom panel so the pass box face is flush with the panel face on both the sending and receiving sides. No external dust-collecting ledge, no recessed face creating a step in the panel surface, and no exposed structural frame members. The panel-to-pass-box junction is sealed with pharmaceutical-grade silicone on both sides — a continuous, inspectable seal that can be verified visually at each cleaning cycle and replaced if deterioration is noted without disturbing the pass box body or its mounting. An optional flange fitting is available for facilities using modular panel systems with a structural profile that requires a positive mechanical attachment of the pass box frame to the panel structural member.
Static Pass Box — Standard Technical Specification
Metrolabs Static Pass Box standard specification — customisable at any parameter:
| Specification | Details |
|---|---|
| Design Type | Static / Passive — No Air Circulation System |
| Cleanliness LevelN/A | Not Applicable — Relies on Room Pressure Differential |
| Standard Internal Dimension | 2×2×2 Ft (60×60×60 cm) |
| Custom Sizes | Available as per application requirements |
| MOC (Standard) | Stainless Steel 304 |
| Illumination | LED Tube Light — flush-mounted inside chamber |
| Air System | Not Available — Passive / Static Design |
| Filters | Not Available |
| Door System | Two-side doors · Glass window · SS handles & SS hinges · Electromagnetic interlocking system |
| Standard Fittings | UV light · Door status LED indicators (Red/Green) · SS handles & hinges |
| Power Supply | 220 Volts / 50 Hz |
Configure Your Static Pass Box — Optional Upgrades & Specialised Configurations
Metrolabs Static Pass Boxes are available with optional accessories and specialised configurations to match your facility requirements, GMP documentation needs, and cleanroom architecture:
SS 316 / SS 316L MOC Upgrade
Upgrade from standard SS 304 to SS 316 or SS 316L for VHP-intensive environments and pharmaceutical Grade A/B suites. SS 316L provides superior pitting corrosion resistance against chloride-containing disinfectants that are standard in pharmaceutical cleanroom environments.
Flange for Modular Panel Mounting
Structural flange at the perimeter of the pass box body for secure bolting to the modular cleanroom panel structural frame — ensuring flush, airtight panel-to-pass-box mounting without silicone-only sealing. Required for panel systems with a structural profile that needs positive mechanical attachment.
Test Certificates
Documentation package including dimensional inspection certificate, material test certificate (MTC) for all SS components, UV-C lamp intensity measurement record, EM interlock function test record, and installation photographs — structured for direct inclusion in GMP IQ documentation at handover.
Mechanical Door Interlocking
Purely mechanical cam-and-lever interlocking mechanism — no electrical components required. Provides the same sequential-access-only rule as the electromagnetic system through a mechanical cam that physically prevents Door B from opening when Door A is open, and vice versa. Suitable for power-unreliable environments or facilities requiring non-electrical interlocking.
Door Buzzer Alarm
Audible door-open alarm — activated when a door remains open beyond the configured time (factory default 30 seconds). Alerts personnel on both sides of the pass box wall to an incomplete transfer procedure — a common occurrence in high-throughput facilities where the user places items in the chamber and walks away before fully closing and latching the door.
UV-C Light Hour Meter
Cumulative UV-C lamp operating hour counter — mounted on the control panel. Enables planned lamp replacement at the manufacturer’s recommended service life (typically 8,000–10,000 hours) before germicidal output falls below the threshold required for effective surface disinfection.
Lead-Lined Configuration
Specialised lead-lined static pass boxes for radiopharmaceutical manufacturing suites and X-ray laboratories where radiation shielding is required at the material transfer point. Lead lining thickness specified to the radiation energy and required attenuation. All other features identical to the standard static pass box.
Polypropylene Interior
Optional polypropylene (PP) interior lining for the transfer of highly corrosive chemical reagents — concentrated acids, alkalis, and solvents that would damage SS 304 or SS 316L surfaces over time. The PP interior is specified where the chemical nature of the transferred materials exceeds the corrosion resistance of stainless steel.
Custom RAL Powder Coat
Powder-coated exterior in any RAL colour — available to match the colour scheme of your cleanroom partition system, gowning room colour coding, or facility corporate colour standards. Maintains a professional and uniform appearance integrated with the surrounding cleanroom panel architecture.
Static Pass Boxes Across Every ISO Class and Regulated Sector
Compact, economical, and hermetically reliable transfer gateways for every cleanroom where pressure integrity — not active decontamination — is the contamination control requirement:
Pharmaceutical GMP
Static pass boxes for Grade B-to-Grade B and Grade C-to-Grade C material transfer. Pressure cascade integrity maintained. UV-C idle disinfection. EM interlock fail-safe. Full GMP IQ documentation including MTC and EM test record at handover.
Hospital Pharmacy
Static pass boxes for sterile preparation room material transfer. NABH compliant. UV-C germicidal standard. Mechanical or electromagnetic interlock. SS 316L option for chlorine-containing disinfectant environments.
Microbiology Labs
Static pass boxes for BSL-2 laboratory material entry and sample removal. UV-C idle disinfection. EM interlock. Standard 2×2×2 Ft or custom dimensions for larger equipment transfer.
Biotech & ATMP
Static pass boxes for same-class zone material transfer in ATMP manufacturing. VHP-compatible SS 316L option. UV-C standard. Mechanical interlock option for VHP-cycle areas where electrical components are undesirable.
Hospital & CSSD
Static pass boxes for sterile instrument transfer between CSSD processing and sterile storage. NABH compliant. UV-C germicidal. Lead-lined option for radiopharmaceutical suite integration.
Research Laboratories
Static pass boxes for NABL-accredited and academic research lab material transfer. Standard 2×2×2 Ft — compact and economical. UV-C idle disinfection. EM or mechanical interlock as required.
Food & Beverage
Static pass boxes for FSSAI high-care food production zone material entry — packaging, ingredients, and tools. Compact, easy-clean design. SS 304 standard. UV-C disinfection between transfer cycles.
Chemical Industries
Static pass boxes for chemical manufacturing cleanrooms — reagent, sample, and tool transfer. Polypropylene interior option for highly corrosive chemical environments. EM or mechanical interlock depending on ATEX zone classification.
High-Accuracy Fabrication — Built for High-Frequency Use
Metrolabs focuses on high-accuracy fabrication and long-term performance — our static pass boxes are built to withstand the high-frequency use of busy pharmaceutical and research environments:
Zero-Ledge Wall-Flush Mounting — Seamless Cleanroom Panel Integration
Every Metrolabs Static Pass Box is designed to be installed level with the cleanroom panel wall surface — the door frame flush with the panel face on both sides, the junction sealed with pharmaceutical-grade silicone, and no external dust-collecting ledges. This design eliminates the most common contamination audit finding associated with pass boxes — the ledge or step at the top of the pass box frame where dust accumulates between cleaning cycles.
Custom Sizing — From Petri Dishes to Bulk Containers
Metrolabs manufactures static pass box chambers to exact dimensional requirements — whether the application requires a compact 300×300×300mm unit for small sample vials in a research laboratory, or an oversized 1200×600×600mm unit for bulk container transfer in pharmaceutical raw material receipt. Standard size is 2×2×2 Ft (60×60×60 cm); customised sizes are available as per application requirements with no minimum quantity requirement for custom dimensions.
Custom Sizes & Aesthetic Integration
Powder-coated options are available to match the cleanroom’s colour scheme and maintain a professional and uniform appearance. Pass boxes can be matched to the RAL colour of the surrounding modular cleanroom panel system — ensuring the pass box is a visually integrated component of the cleanroom architecture rather than an industrial unit inserted into a controlled environment.
Ergonomic Transfer Height — Straight-Line Protocol, Minimum Door-Open Time
Metrolabs recommends mounting the static pass box at a height that supports ergonomic straight-line transfers — the transfer item moved horizontally at the correct ergonomic height from the sending shelf to the pass box chamber to the receiving shelf without lifting, tilting, or repositioning. Straight-line transfers reduce the time the door remains open (less exposure of room air to the chamber), reduce the risk of item dropping during transfer, and support the correct transfer procedure without requiring operator training beyond the basic protocol.
Static Pass Box vs Dynamic Pass Box vs Standard Hatch
Static vs Dynamic: Choose the Static Pass Box for same-class transfers where pressure integrity is the contamination control requirement. Choose the Dynamic Pass Box when materials are crossing from a lower to a higher ISO class and require active HEPA Grade A decontamination of item surfaces before entry. See Dynamic Pass Box →
From Specification to Installed & Documented Static Pass Box
Metrolabs manages the complete static pass box supply process:
Specification & Design
ISO classes of both rooms confirmed. Transfer material type assessed (size, fragility, frequency). MOC (SS 304 / SS 316L), internal dimensions (standard 2×2×2 Ft or custom), interlock type (EM / mechanical), optional features (flange / door buzzer / UV hour meter / specialised interior), and mounting configuration confirmed. Dimensioned drawing produced and signed off before fabrication.
Precision Fabrication
Interior chamber fabricated — SS 304 or SS 316L — coved corners. Exterior body SS 304 brushed. EM interlock PCB installed and tested. Silicone door gaskets fitted. Double-glazed glass vision panels installed flush to door frame. UV-C lamp mounted and interlocked. LED status indicators fitted. SS handles and hinges installed. ASTM A967 passivation performed. MTCs issued.
Installation & Commissioning
Pass box installed into cleanroom panel aperture — flush-mounted to panel face on both sides. Panel-to-pass-box junction sealed with pharmaceutical-grade silicone. Electrical connections made. EM interlock function tested (both door sequences, fail-safe power loss test). UV-C interlock tested. UV-C cut-off safety verified. LED status indicator sequence verified. Door buzzer tested (if fitted).
IQ Documentation
SS MTCs, ASTM A967 passivation cert, EM interlock function test record, UV-C interlock test record, UV-C lamp intensity measurement, door gasket specification, LED indicator test record, and installation photographs compiled as static pass box IQ documentation for GMP facility qualification submission at handover.
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