A pass box that performs well at the factory is not the same thing as a pass box that is ready to accept into a GMP or classified-area workflow. The gap between those two states is exactly what FAT and SAT are built to close, and how a project team manages that gap determines whether acceptance evidence actually supports the installed, operating unit or merely documents a unit that once worked somewhere else.

Evidence That Belongs at FAT and What Must Wait for Site Installation

A factory acceptance test exists to confirm that the equipment, as built, matches what was ordered and configured before it leaves the manufacturer’s control. This means FAT can meaningfully verify the physical chamber construction, the installed control logic, the interlock behavior between doors, the alarm functions tied to door status or pressure deviation, and the completeness of the records generated during manufacture. All of these are properties of the unit itself, independent of where it will ultimately sit.

What FAT cannot verify is anything that depends on the installed environment. A pass box’s interlock might behave correctly on a factory bench using simulated inputs, but the same interlock’s interaction with an actual building management system, a specific door orientation relative to adjoining rooms, or utility supply conditions at the final location cannot be confirmed until those conditions exist. Where a project specifies signal integration with an external monitoring system, that integration is by definition a site-dependent item, because the external system is not present at the factory.

This distinction changes how a buyer should read a FAT report. A report that is silent on site-dependent items is not necessarily incomplete — it may simply reflect that those items were correctly identified as out of scope for a factory test. What matters is whether the report explicitly names what was deferred, rather than leaving an ambiguous boundary between what was tested and what was assumed. A buyer reviewing a FAT package should be able to distinguish, for every check on the test plan, whether it was executed under factory conditions, executed under simulated conditions standing in for the site, or explicitly carried forward as an open item pending installation. Where that distinction is blurred, the FAT result risks being treated as broader evidence than it actually provides, and the project team may arrive at SAT without a clear list of what remains to be proven.

Tracing Interlocks, Alarms, Controls, and Records to the URS

Interlocks, alarms, and control logic are not generic features that either exist or do not; they are implementations of specific requirements that were presumably defined earlier in the project, in the user requirement specification. The practical discipline here is traceability: every interlock behavior tested at FAT or SAT should map back to a stated requirement, rather than being tested because it is conventional to test it.

This matters because pass box configurations differ according to their intended function. A static pass box, a dynamic pass box, and a VHP pass box or VHP chamber each carry different interlock logic appropriate to their purpose — a static unit’s interlock may concern only simultaneous door opening, while a dynamic or VHP-capable unit’s interlock and alarm scheme may also need to account for airflow state, pressure differential, or cycle completion before a door can release. If the URS specifies a particular interlock behavior, control sequence, or alarm condition, the acceptance test for that unit should be able to demonstrate exactly that behavior — not a generic pass-box interlock pattern assumed to be equivalent.

Where a requirement calls for an alarm on loss of differential pressure, the test should confirm the alarm trips under the condition the requirement describes, and the record should show which requirement that test addresses. Where a requirement calls for a specific door sequencing logic, the same applies. This becomes especially important when a unit includes optional accessories — pressure gauges, UV lamps, or additional alarm points — since these components only have meaning in relation to the function they were specified to protect. A control or alarm untested against its originating requirement leaves a gap that is easy to overlook when the overall test record appears complete, because completeness in volume of tests performed is not the same as completeness in requirement coverage. The buyer’s task is to confirm that every control element with a stated requirement has a corresponding test result, and that the test result is linked back to that requirement rather than standing alone as a pass/fail entry.

Testing Airflow, Pressure, Leakage, and Decontamination Within Defined Boundaries

Airflow, pressure, leakage, and decontamination performance are the areas where it is most tempting to reach for a standard number, and where doing so is least defensible. These test areas only have meaning in relation to the specific intended use of the equipment and the protocol that was approved for the project — the same physical pass box tested against two different protocols, for two different applications, could reasonably be held to two different acceptance criteria.

ISO 14644-3 describes test methods and apparatus applicable to cleanrooms and associated clean zones, but the methods it describes are procedural: they explain how a test may be performed, not what value constitutes acceptance for a given piece of equipment. Applying a method from this source without also applying project-specific acceptance limits only verifies that a measurement was taken correctly, not that the result is adequate for the application. Similarly, EU GMP Annex 1 identifies categories of installed tests — filter integrity, airflow, pressure, visualization, and recovery — that are relevant once equipment is installed and operating in its intended grade of environment, but which specific tests apply, and at what criteria, depends on the grade the equipment serves, the equipment’s function, the risk associated with its use, and the test method chosen to evaluate it.

This has a direct configuration consequence. A pass box intended to maintain a pressure cascade between two differently classified spaces requires a pressure differential test with criteria tied to that cascade’s design intent, not a generic differential value. A VHP pass box intended to achieve a validated decontamination cycle requires decontamination verification tied to the specific cycle parameters and log reduction target the project has approved, not an assumption that any VHP cycle is equivalent to any other. Leakage testing for door seals likewise depends on what the seal is meant to prevent — ingress of unfiltered air, egress of a contained material, or both — and the acceptance rate must follow from that purpose.

The practical implication is that a buyer should ask for the approved protocol before asking for the test result, because a passing result against the wrong criteria is not useful evidence. Where the intended use has not yet been fully translated into protocol-level criteria, that translation is itself an open item that should be resolved before FAT or SAT results are treated as conclusive.

Verifying Utilities, Signals, Door Orientation, and Room Interfaces at SAT

SAT exists precisely because some properties of a pass box cannot be verified until it is installed in its final location, connected to its actual utilities, and oriented against the rooms it serves. Utility verification confirms that power, and where applicable compressed air or other service connections, are present and functioning as the equipment requires — a condition that cannot be assumed from factory testing because factory power and site power are not the same supply.

Door orientation deserves particular attention because it is a site-specific configuration decision with consequences for the interlock logic verified earlier. A pass box installed with its doors facing the wrong adjoining spaces, relative to the pressure cascade or classification difference the project intends to maintain, does not fail because the equipment is defective — it fails because the installation does not match the intended use the interlock was designed to protect. Confirming door orientation at SAT is therefore not a formality; it is a direct check that the physical installation matches the assumption behind the control logic already tested at FAT.

Signal integration is the other category that only becomes testable on site. A pass box’s alarm or status outputs may need to report to a building management system, a monitoring platform, or another piece of integrated equipment. Whether those signals actually transmit correctly, and whether the receiving system interprets them as intended, cannot be known until both ends of that connection exist in their final form. Where a project’s control architecture places interpretation logic in the receiving system rather than in the pass box itself, SAT becomes the only point at which that full chain can be verified end to end.

Room interface checks more broadly confirm that the pass box’s physical boundary — its mounting, its sealing against the wall or partition, its relationship to adjoining finishes — matches what the room design assumed. A unit that performed correctly as a standalone item at FAT can still fail a room interface check if the surrounding construction does not match the equipment’s intended fit. None of these checks substitute for one another; a facility with confirmed utilities but unconfirmed door orientation has not completed SAT, regardless of how much of the test plan has been executed.

Recording Instruments, Witnesses, Deviations, Retests, and Open Items

The documentation generated during FAT and SAT carries its own structure, and the quality of that structure determines whether the acceptance record is actually usable during later qualification stages. A witnessed test result is only informative if it is linked to the specific user requirement it was meant to demonstrate; a witness signature on an unlabeled test confirms that something was observed, not what was proven.

Instrument records — the calibration status and reading of whatever measuring device produced a test result — need to travel with the test they support rather than being filed separately. A pressure differential reading is only as credible as the instrument that produced it, and a reviewer checking the record later should be able to find both together without having to reconstruct which instrument was used for which test.

Deviations require the same treatment. Where a test does not meet its criteria on first attempt, that deviation should remain visibly linked to the affected test and the requirement behind it, rather than being resolved quietly through a retest with no visible trail back to the original failure. A retest result, in turn, should be recorded against the same requirement, so a reviewer can see both that a problem occurred and that it was subsequently resolved — or, if it was not resolved, that it remains open.

Open items carry the most consequence for project planning, because they represent work that has not yet produced acceptable evidence. Where an open item is left unlabeled or folded into a general list without a link to the specific requirement it affects, there is a risk that the item is overlooked when the project moves toward the next qualification stage. A FAT or SAT package that reads as entirely successful, but which does not clearly show its open items against their requirements, can create a false impression that the equipment is further along in its acceptance than the evidence actually supports. The discipline of keeping every witnessed test, instrument record, deviation, retest, and open item traceable to its requirement is what allows a later reviewer — whether in validation, QA, or at handover — to reconstruct exactly what has been proven and what has not.

Acceptance Handover After Factory and Site Responsibilities Are Closed

Handover is the point at which responsibility for the pass box’s acceptance evidence shifts from a testing activity to a qualification record that later stages will rely on. For that shift to be sound, both factory and site responsibilities need to be demonstrably closed — not merely scheduled, assumed, or implied by the passage of time.

Closing factory responsibility means the FAT record shows, for every item on the original test plan, either a completed and traceable result or an explicit note that the item was deferred to site, with the reason stated. Closing site responsibility means SAT has addressed every deferred item, along with the installation-specific checks — utilities, door orientation, signal integration, room interfaces — that only become testable once the unit is in place. Where the project’s intended use includes decontamination performance, as with a VHP pass box or VHP chamber, closing that responsibility also means the decontamination verification has been executed against the approved protocol rather than left as an assumption carried from FAT.

The buyer’s project information plays a direct role here, because the acceptance criteria applied during both FAT and SAT trace back to the intended use and configuration the buyer specified during order and quotation review. Information supplied at that stage — the classification context the unit serves, the pressure relationship it must maintain, whether VHP decontamination capability is required — becomes the basis against which Youth Filter’s configuration is built and against which the eventual test protocols are written. A handover record that does not align with that original specification signals a gap that needs resolution before the unit is treated as accepted, regardless of how many individual tests passed.

Where a project has confirmed all factory and site items with full traceability to the URS, handover can proceed on the basis that the equipment and its installation match what was intended. Where open items remain — whether from FAT carried forward, or from SAT checks not yet executed — the handover record should state them plainly rather than resolving them by omission, so that whoever takes responsibility for the equipment next, whether for qualification, operation, or maintenance, inherits an accurate picture of what has and has not been demonstrated.

Frequently Asked Questions

Q: How do we decide whether a pass box test belongs at FAT or SAT?
A: Use FAT for checks that can be completed on the configured chamber under agreed factory conditions. Carry a check to SAT when it depends on installed utilities, room interfaces, door orientation, signal integration, or other agreed site conditions.

Q: What must be agreed before airflow, pressure, leakage, or decontamination results can be accepted?
A: Define the acceptance criteria in the approved protocol from the intended use, equipment function, cleanroom grade, project risk, and applicable test method. Do not substitute a generic pass box value for project- and equipment-specific limits.

Q: What information should the buyer prepare before FAT begins?
A: Prepare the approved user requirements, configured equipment scope, control and alarm requirements, available factory test conditions, and the intended site interfaces. This lets each witnessed test and record be traced to a requirement and exposes site-dependent checks before shipment.

Q: Can the same acceptance plan be used unchanged for static, dynamic, and VHP pass boxes?
A: The plan should follow the configured pass box function and approved intended use. Confirm which airflow, pressure, leakage, decontamination, control, and interface checks actually apply, then assign each applicable check to factory or site evidence.

Q: How should deviations, retests, and open items be handled at handover?
A: Link each item to the affected test and user requirement, retain the relevant instrument and witness records, and record the current retest evidence. Keep unresolved site-dependent checks open until their SAT evidence and responsibility are closed.