When the simplest box is the right box
Static Pass Box
A static pass box has no fan and no filter. In the right place that is not a shortcoming. It is the whole point. The skill is knowing exactly which place that is.
- Same-grade transfers
- Electromagnetic interlock
- SS 304 / SS 316
- No HEPA filter, by design
What a static pass box is
The simplest transfer hatch is the static pass box. It is an interlocked, stainless-steel chamber set into a cleanroom wall, with no air treatment inside. It lets material cross between two areas of the same cleanliness grade, without a person walking through.
- ISO 14644-1
- EU-GMP Annex 1
- Schedule M
- WHO-GMP
- SS 304 / SS 316
The one-line test
Same grade on both sides of the wall? A static box is enough.
Change the grade and the same box becomes the cheapest way to move contamination across a boundary you paid to create.
You skip the cost, the power and the validation of a fan and filter. "Static" means the air in the box just sits there. The box isolates, it does not clean.
That makes it exactly right in one situation and quietly wrong in another, which is what choosing one comes down to. The rest of this page is about telling those two situations apart, because the box itself is the easy part.
Fabtech has delivered 2,000+ controlled environments since 2004, across every industry that needs controlled air. Each one was designed, built and validated in-house by one accountable team. So when we tell you a static box is enough, it is the same team that would have sold you the dynamic one saying so.
- Air treatment
- None. No HEPA filter and no blower, by design
- Suits
- Same-grade transfers, low risk
- Interlock
- Electromagnetic, both doors can never open together
- Body
- SS 304 as standard, SS 316 for aseptic or corrosive duty
- Typical step across a grade boundary
- 15 Pa
- States in one transfer: load, wait, remove
- 3
- Standard chamber, 2 ft cube to 3 ft cube
- 600 to 900 mm
- Germicidal lamp, fitted as standard
- UV
When a static box is right, and when it's a false economy
A static box earns its place by doing less. The same box, in two different walls, is either the correct specification or the cheapest possible mistake. Here are both, drawn side by side.
- Material route
- Unfiltered air and its particle load
- Built structure
FIG. 01One chamber, two walls. State A is a same-grade transfer, where a static box is the correct specification. State B is the same box across a 15 Pa grade boundary, where unfiltered air and its particle load enter the chamber and nothing is fitted to remove them.
A static box earns its place by doing less. Use one when
- 01
Both sides are at the same grade
And the transfer is low-risk: moving documents, tools or packaged items within a classified zone, or between two areas held to the same standard.
- 02
A dynamic box would be over-specified
Paying for a fan, a filter and HEPA-integrity validation that the boundary simply doesn't call for.
It becomes a false economy the moment the material has to step up a cleanliness grade. Picture an unclassified corridor opening into a classified suite. A static box does nothing to the particles the material carries from the dirtier side. It just moves the contamination across with it.
Dynamic pass box, HEPA airflow VHP pass box, bio-decontamination
State A
Same grade both sides
Static pass box, correctly specified
State B
Across a grade boundary
Static pass box, wrongly specified
- Pressure differential across the wall
- None, same grade
- About 15 Pa
- Air entering the chamber
- Advantage. Same grade air
- Unfiltered air
- Particle load carried in
- Advantage. None to speak of
- Yes, with the material
- What purges the chamber
- Nothing needs to
- Nothing is fitted
- The right specification
- Advantage. Static pass box
- Dynamic pass box
- Validation that applies
- Interlock, cleanability, UV
- Adds airflow and HEPA integrity
FIG. 02The same chamber, judged against the same six questions, in the two walls drawn above.
A static box is the right call when both sides sit at the same cleanliness grade. Once the grade changes, the box would carry particles across the boundary with the material. A dynamic box is then usually the safer specification.
Where a static box fits, and where it doesn't, is a judgement best made when the room's grade boundaries are designed, not picked from a catalogue.
Static, or step up?
Read the wall, not the catalogue. The boundary decides the box, and there are only three answers.
| The boundary | The boxTHIS PAGE | What the box has to do |
|---|---|---|
| Both sides at the same grade, low risk | Static pass box, this page | Isolate the two rooms during transfer. Nothing more is asked of it. |
| Any step up in cleanliness class | Dynamic pass box | Strip particles off the material with HEPA-filtered airflow before the clean door opens. |
| Into a sterile or aseptic area | VHP pass box | Bio-decontaminate the chamber and its load, not just remove particles. |
FIG. 03Boundary-to-equipment mapping, as specified on Fabtech projects.
The full side-by-side detail, air treatment, validation depth and cost, is set out in the static vs dynamic vs VHP comparison. Static vs dynamic vs VHP
How a static pass box works
The static pass box working principle is deliberately plain, and the plainness is the feature.
No fan. No filter. One active idea:the electromagnetic interlock.
01
Load and close
An operator places the material inside and closes the door on their side. The electromagnetic interlock locks the opposite door, so both can never be open at once.
02
Wait
The material sits in the sealed chamber. A UV germicidal lamp is fitted as standard. It can be run for limited line-of-sight surface disinfection of the empty chamber between transfers. It treats directly-lit surfaces only, not shadowed or packaged material.
03
Remove
A colleague on the other side opens their door and removes the material. The first door is locked for as long as the second one is open.
- Door free to open
- Chamber and wall
FIG. 04The three states of a static transfer. The electromagnetic interlock is the only active component: it is what guarantees the two rooms are never joined by an open air path.
There is no HEPA filter and no blower, and that is deliberate. A static box is not trying to clean the material. It is trying to isolate the two rooms. A clean door never has to open onto the corridor, and nobody has to carry contamination across on foot.
When both sides are already at the same grade, that is enough.
Key components of a static pass box
There is not much inside a static box, and that is the design. Two doors that cannot open together, a chamber you can clean properly, and a lamp. Nothing else has to keep working for the box to do its job.
Electromagnetically interlocked doors
The core feature: both doors can never open together, so the two rooms are never joined by an open path.
Stainless-steel body
SS 304 as standard, and SS 316 where the duty is aseptic or the cleaning chemistry is corrosive.
Coved internal corners
So there is no square corner for residue to sit in, and the chamber can be wiped out properly.
UV germicidal lamp
Fitted as standard: a between-transfers treatment for the empty chamber, limited to the surfaces the lamp can actually see.
Door interlock indicators
Status lights that tell an operator which door may open, so the interlock is legible from both sides of the wall.
No HEPA filter and no blower
By design. That absence is what makes it a static box, and it is why the qualification that follows it is shorter.
Standard chambers run from 600 × 600 × 600 mm (2 ft cube) up to 900 × 900 × 900 mm (3 ft cube). Within that, the opening and the depth follow the biggest item you need to pass, and the wall the box sits in.
Where static pass boxes are used
Static boxes suit transfers within a single classified area, or between two areas of the same grade.
- PharmaceuticalSecondary-packaging and warehousing zones held to the same grade.
- Hospitals and labsDocument and sample transfer, where isolation is what's needed and air cleaning is not.
- Electronics handlingTransfers between areas of the same grade on an assembly or test floor.
- Low-risk material flowAny route where the two sides are already at the same cleanliness level.
Where the cleanliness grade changes across the wall, a dynamic or VHP box replaces it. That is the only test worth applying, and it is worth applying it wall by wall rather than once for the whole building.
Standards and validation
Whether a static box is allowed on a given wall is not really a question about the box. It is a question about the two rooms it joins.
The grades on either side decide it, and those grades are the ones set by ISO 14644-1. For pharmaceutical manufacture, the same expectations reach you through EU-GMP Annex 1. In India they also arrive through Schedule M and WHO-GMP. None of that is written about static boxes. It is written about the rooms either side of one.
The good news is the paperwork. Qualifying a static box is genuinely less work than qualifying a dynamic one. There is no airflow to qualify and no filter to integrity-test. What is left is short, and it is set out here.
| What gets qualified on a static pass boxTHIS PAGE | What that means |
|---|---|
| Interlock function | Both doors must never be open at once. |
| Construction and cleanability | The body and its coved corners can be cleaned properly. |
| UV function | The lamp is fitted as standard, so it is checked. |
| HEPA integrity testing (PAO/DOP) | Not run. No filter is fitted to test. |
| Airflow qualification | Not run. No fan, so there is no airflow to qualify. |
| On a dynamic box | Those last two sit inside its DQ/IQ/OQ/PQ. |
FIG. 05Qualification scope for a static transfer hatch, against ISO 14644-1 and EU-GMP Annex 1 room grades.
That shorter qualification is a real part of why a static box costs less to own, not just less to buy. The paperwork is lighter, so there is less for your validation team to carry. We handle the equipment validation and AMC for the unit either way, so the shorter route doesn't land back on your desk.
Cleanroom validation and qualification ISO classification of cleanrooms
How Fabtech approaches static transfer
Tell us the two rooms a box would sit between, their grades, and what's crossing the wall. Our engineers will give you a straight answer on whether a static box is the right economy, or whether that boundary needs more. If it helps the call, we can walk you through a named static-pass-box reference too.
Fabtech Cleanrooms is a cleanroom equipment manufacturer that designs, builds and validates controlled environments across India. It manufactures static pass boxes in-house, supplied both as standalone products and integrated within turnkey cleanroom projects.
Deciding where a static box is the right economy is part of that design work. Choosing a static box rather than a dynamic one is a grade-boundary decision. Get it right and you are neither paying for airflow you don't need, nor under-specifying a boundary that does.
Fabtech has delivered HEPA-filtered, classified cleanrooms for pharma and research clients across India. That work includes Ajanta Pharma, Desano and German Remedies, plus BSL-3 facilities at PGICH Noida and ASMC Shahjahanpur. It is the same contamination-control engineering that decides where a static box is and isn't acceptable.
Turnkey cleanroom solutions Cleanroom equipment range Talk to an engineer about your transfer points
- Ajanta PharmaOSD facility, Aurangabad
- DesanoPharma cleanrooms, Bangalore
- PGICH NoidaBSL-3 facility
- ASMC ShahjahanpurBSL-3 facility
Static pass boxes, common questions
A static pass box is an interlocked transfer chamber with no air treatment inside. It moves material between two areas of the same cleanliness grade, without a person walking through. It isolates the two rooms. It does not clean the material.
A static box passively isolates two areas of the same cleanliness. A dynamic box adds HEPA-filtered airflow to strip particles off the material when it moves between different grades.
To isolate two cleanroom areas during material transfer. It saves opening a clean door to a less-clean corridor, or walking a person across, where both sides are already at the same cleanliness level.
When both sides of the wall are at the same grade and the transfer is low-risk. Once the grade changes, a dynamic box is usually the right choice instead. Into a sterile area, that becomes a VHP box.
No. By design it has no filter and no blower. If HEPA-filtered airflow is needed, because the two sides sit at different cleanliness grades, a dynamic pass box is used instead.
Yes, but a shorter one. With no fan or filter, there is no airflow test and no HEPA-integrity test to run. Qualification comes down to interlock function, construction and cleanability, plus UV function.
Standard chambers run from 600 × 600 × 600 mm up to 900 × 900 × 900 mm. The opening and the depth follow the biggest item you need to pass, and the wall the box sits in.
No. The UV lamp is a line-of-sight treatment for the empty chamber between transfers. It treats directly-lit surfaces only, not shadowed or packaged material, so it does not make a static box acceptable across a grade boundary.
Tell us about the two rooms
Share the grade on each side of the wall and what's crossing it. Our engineers respond with a straight answer on whether a static box is the right economy, or whether that boundary needs more.