Operating Theatre Environmental Verification
Filter leakage, recovery, visual airflow assessment and protection-level measurement supporting initial acceptance and periodic verification of operating theatres, where required by the applicable healthcare standard.
Verification activities and measurement scope
Four complementary activities may form part of an operating-theatre verification programme. The applicable activities and acceptance criteria are established by Indian regulatory, accreditation and project requirements for the facility.
Filter leakage tests
Verification that the installed ceiling filter system does not allow local leakage once assembled into its frame and housing.
View activity →Recovery-time measurement
Characterisation of how airborne particle concentration decays toward the specified condition after a controlled challenge.
View activity →Airflow visualisation and outflow assessment
Observation of airflow behaviour in unidirectional-flow areas using visible fog, ahead of or alongside quantitative measurement.
View activity →Protected-zone degree-of-protection measurement
Evaluation of the protective effect at the protected zone, where the governing requirement specifies it.
View activity →Governing references
DIN 1946-4Ventilation in buildings and rooms of health care ISO 14644-3Test methods shared with cleanroom work — filter leakage, recovery and airflow SWKI VA105-01Regional operating-theatre verification contextThese are regional or project-specific references and are not automatically Indian statutory requirements. The applicable scope for an Indian facility is set by national and state regulation, accreditation requirements and the project specification.
Installed ceiling filter integrity
The ceiling filter array of a unidirectional-flow theatre is an installed filter system in exactly the sense the cleanroom method addresses: media, frame, gasket or gel seal, mounting arrangement and accessible housing interfaces, all of which can allow local leakage that the filter element alone would not.
The measurement chain is the same one used for a cleanroom ceiling — a challenge aerosol upstream, a diluted upstream reference measurement, and a systematic downstream scan with a rectangular isokinetic probe matched to the particle-counter flow.
Full filter-integrity method →
Recovery performance measurement
A controlled particle challenge is introduced and the decay of particle concentration is measured to characterise how the theatre returns toward its specified condition. The result belongs to the specific room, its ventilation system and the challenge used; it is not a transferable figure.
Technologies: an ATM 228 challenge-aerosol generator and a CPA 341 particle counter, with the result recorded and evaluated in software.
Airflow visualisation and outflow assessment
In a unidirectional-flow theatre, the question the fog answers is whether the displacement flow actually reaches the protected zone intact. Fog makes visible where flow separates around the surgical light head, around suspended equipment and around the surgical team; where the boundary of the unidirectional field actually lies; and how air behaves at the transition to the surrounding room.
This is a qualitative observation method. It is the natural first test because it tells you where to look, but it does not produce a velocity value and does not replace quantitative measurement where the applicable standard specifies one.
Fog-generation quality and flow-disturbance control
A pulsing or turbulent fog source introduces its own disturbance into the field being assessed. The CFG 291 combines optimised fluid guidance with a purpose-built evaporator to produce a uniform, low-pulse output, and the spot probe places the fog precisely where the observation is needed.
View the CFG 291 →Protected-zone degree-of-protection measurement
Protection-level measurement asks a different question from classification. It does not ask how clean the room is; it asks how effectively the protected zone is being shielded from the air around it.
A test aerosol is released at the periphery, outside the protected zone. One measurement is taken there as the reference, and a second inside the protected zone. The protective effect is derived from the relationship between the two, in the manner and against the acceptance criterion set by the governing requirement.
Topas associates protection-grade operating-theatre measurement, in its ADD 536 documentation, with DIN 1946-4 and SWKI VA105-01, both regional references applied where the project or the local regulation calls for them. The same documentation also cites VDI 2167 Part 1, which has since been withdrawn — current project requirements should be established from the applicable healthcare ventilation standard and the project specification rather than from that sheet.
The Topas ADD 536 is the aerosol distribution and dilution system used for protection-grade measurement in operating theatres where the applicable healthcare test method requires it. Its configuration follows the protected-zone geometry, measurement positions and acceptance method defined for the project.
Standards applicability and regional context
Operating-theatre ventilation verification is governed regionally. The references below are the ones most often cited in this field internationally.
| Reference | Edition / status | Context |
|---|---|---|
| DIN 1946-4 | 2018-09 + A1:2025-11 — Current published reference | Operating-room and health-care ventilation verification where applicable |
| SWKI VA105-01 | Current published reference | Swiss and regional operating-theatre verification context where applicable |
| ISO 14644 / ISO 14644-3 | 2019 (Edition 2) — Current published reference | General cleanroom and controlled-environment context, and test-method context for filter leakage, recovery and airflow |
Scroll the table horizontally →
These are regional and project-specific references. They are not automatically Indian statutory requirements. The applicable verification scope, method and acceptance criteria for an Indian healthcare facility are set by the applicable national and state regulation, the accreditation requirements that apply to the facility, and the project specification.
The Topas cleanroom test equipment documentation lists this healthcare ventilation reference as “EN 1946-4” while quoting the title associated with DIN 1946-4 (ventilation and air conditioning — ventilation in buildings and rooms of health care). Confirm the exact designation and edition applicable to the project before citing it on a project document.
Verification measurement technologies
Each verification activity uses a different combination of challenge source, measurement and sampling. The table maps that; the products below are the items themselves.
| Activity | Challenge / source | Measurement | Sampling |
|---|---|---|---|
| Filter leakage | ATM 228 challenge aerosol | CPA 341 upstream reference and downstream detection, with DIL 544 dilution on the sampled branch | SYS 529 rectangular isokinetic probe |
| Recovery | ATM 228 challenge aerosol | CPA 341 concentration decay | Direct sampling at the defined location |
| Airflow visualisation | CFG 291 condensation fog | Visual observation and recording | Not applicable — qualitative method |
| Degree of protection | Test aerosol at the periphery | Paired particle measurement inside and outside the protected zone | Positions set by the governing requirement |
Scroll the table horizontally →
CFG 291Visual airflow and outflow testing in the unidirectional-flow area.- TopFog fluid
- Approx. 25 min run
- Spot probe
CPA 341Filter-leakage, recovery and protection-level measurement positions.- 0.3 – 10 µm
- 28.3 L/min
- 5 size classes
ATM 228Challenge aerosol for theatre filter-leakage and recovery activities.- 20 – 250 L/h
- Integrated compressor
- Mobile
DIL 544Dilution of the sampled upstream branch.- 1:100
- 28.3 L/min
- Automatic setting
SYS 529Scanning the theatre ceiling filter array.- 28.3 L/min
- 31 – 47 cm/s
- Rectangular
Verification software and configured systems
These supporting technologies are specified against the verification method, interfaces and protected-zone geometry required for the project.
OPQWin
OPQWin supports Topas operating-theatre measurement and evaluation workflows. Software scope, interfaces and version are confirmed against the required verification method before project specification.
It is not generic cleanroom software. CRQWin is the separate application for cleanroom qualification, classification, filter-integrity and recovery evaluation, and the two should not be substituted for one another.
CRQWin in the filter-integrity chain →ADD 536
Aerosol distribution and dilution system for protection-grade measurement in operating theatres, where the applicable healthcare test method requires it. Configured against the project and the measurement positions set by the governing requirement.
Discuss a project requirement →
Operating-theatre verification system configuration
Share the theatre ventilation concept, the ceiling filter arrangement, the verification activities the applicable standard requires and the reporting the facility needs.