NABH Requirements for Operation Theatres: A Practical Checklist

NABH does not publish a standalone engineering code for operation theatres. It assesses three different things: that the theatre was designed to a recognised standard, that it demonstrably performs to the parameters you designed it to, and that you hold the records to prove both. Hospitals with genuinely good theatres fail on the third far more often than on the first two.

That distinction splits OT compliance into two halves with two different owners. One half is built into the room and delivered by whoever constructs it — air change rate, filtration, pressure cascade, finishes, gas terminals, earthing. The other half is generated continuously by the hospital that runs the theatre — traffic discipline, environmental logs, surveillance cultures, calibration schedules, checklists. No contractor can hand over the second half. No amount of process discipline rescues a theatre whose air handling plant was undersized on day one.

This article separates the two explicitly, because being clear about the boundary is the single most useful thing a quality manager and a project engineer can agree on before an assessment cycle begins.

The boundary: builder scope versus hospital scope

Requirement area	Delivered by the builder	Generated by the hospital	What the assessor actually sees
Air changes, filtration, pressure cascade	Design, plant, ducting, terminal HEPA, commissioning validation	Filter replacement, re-validation, differential pressure logs	A validation report plus a current log that agrees with it
Cleanliness class	Room sealing, air distribution, filter grade	Periodic re-classification, discipline on door openings and occupancy	Particle count certificate with occupancy state stated
Temperature and humidity	Sized cooling and reheat/dehumidification capacity	Daily logging, sensor calibration, out-of-range escalation	Twelve months of logs and a calibration certificate
Surfaces and finishes	Seamless panels, coved junctions, epoxy floor, hermetic doors	Cleaning protocol, damage repair, no adhesive signage on panels	Physical inspection and the cleaning schedule
Medical gas inside the OT	Terminals, AVSU, pipework, area alarm, certification	Zone valve training, alarm response drill, purity re-test	Test dossier plus staff who can point to the shut-off valve
Electrical safety	Earthing, IPS/LIM where specified, UPS, essential-power segregation	Earth resistance re-test, UPS battery records	Test reports with dates inside the cycle
Lighting	Surgical luminaire, ambient lighting design	Lux verification, lamp replacement records	Measured lux against a stated target
Clinical process	Nothing	Surgical safety checklist, counts, consent, PACU criteria, SSI surveillance	Audited records and observed practice

Read the right-hand column carefully. In almost every row, the assessment turns on a document rather than on the hardware. A theatre can be engineered to a very high standard and still lose points because the last particle count was fourteen months ago, or because the anemometer used to measure air velocity had no valid calibration certificate.

Where OT requirements sit inside the NABH standard

The Hospital Accreditation Standard is organised into chapters by function, not by department. There is no chapter titled “Operation Theatre.” OT evidence is distributed across most of the standard, which is why a room-by-room preparation approach tends to leave gaps.

Chapter	What it pulls from the OT
Care of Patients (COP)	Pre-anaesthesia assessment, informed consent, surgical safety checklist, instrument and sponge counts, anaesthesia record, post-anaesthesia recovery and discharge criteria
Hospital Infection Control (HIC)	Environmental surveillance, sterilisation and CSSD interface, hand hygiene and scrub facilities, traffic control, biomedical waste segregation, surgical site infection surveillance
Facility Management and Safety (FMS)	The physical plant — ventilation, utilities, medical gas, electrical safety, fire safety, equipment maintenance and calibration, planned preventive maintenance
Patient Safety and Quality Improvement (PSQ)	Surgical outcome indicators, SSI rates, adverse event reporting, re-exploration and cancellation rates
Management of Medication (MOM)	Anaesthetic agents, emergency drug trolley, narcotics custody, look-alike/sound-alike controls
Human Resource Management (HRM)	Credentialing and privileging of surgeons and anaesthetists, competency records, BLS/ACLS currency
Information Management System (IMS)	Record completeness, retention and confidentiality of operative notes

The practical response is to build a cross-reference index that maps each chapter to the OT evidence that satisfies it, and to keep that index at the front of the OT file. An assessor works chapter by chapter and will ask the same theatre four different questions from four different directions.

Edition caveat, and it matters. NABH revises the Hospital Accreditation Standard periodically, and objective elements are re-numbered, merged and re-weighted between editions. Nothing in this article should be treated as a quotation from a specific clause. Confirm which edition your assessment will be conducted under, download the current standard and the current assessment guidebook from NABH directly, and reconcile any checklist — including this one — against it.

Environmental parameters: targets and how each is verified

This is the table most quality managers want. Every figure below is a widely used design target in Indian practice, drawn from the convergence of NABH expectations, HTM 03-01, ASHRAE 170, ISO 14644 and Indian tender convention. They are not quotations from a mandatory Indian code, because no single mandatory Indian OT engineering code exists. Verify against your own design basis and the current edition of whichever standard your specification names.

Parameter	Typical target, general major OT	How it is verified	Typical re-verification
Total air changes per hour	20 ACH minimum; 25–30 ACH commonly specified for cardiac, neuro, transplant and joint replacement	Supply air volume measured by balometer or duct traverse, divided by room volume	Annually, and after any AHU, duct or filter change
Fresh air component	Typically 4 ACH or ~20% of supply, whichever is higher	Measured at the AHU fresh air intake	Annually
Filtration train	Pre-filter, fine filter, terminal HEPA to EN 1822 (H13 or H14)	Filter test certificates plus in-situ integrity scan with a PAO/DOP aerosol challenge	Integrity test annually; media replacement typically 2–3 years or on differential pressure
Air cleanliness class	ISO Class 7 in a conventional OT; ISO Class 5 within an ultraclean surgical canopy	Discrete particle counting to ISO 14644-1	Per ISO 14644-2: commonly 6 months for ISO 5 and cleaner, 12 months for ISO 6–9
Pressure differential	Positive to all adjacent spaces; ≥2.5 Pa is the common floor, with many Indian specifications working a 5–15 Pa cascade	Calibrated micromanometer, plus a permanently mounted differential pressure gauge or monitor visible at the door	Continuous indication; instrument calibration annually
Temperature	21–24 °C, adjustable at the surgeon control panel	Calibrated sensor on the return path, logged	Continuous logging; sensor calibration annually
Relative humidity	Commonly 30–60% RH; many Indian specifications tighten to 45–60%	Calibrated RH sensor, logged	Continuous logging; sensor calibration annually
Surgical field illumination	Surgical luminaire certified to IEC 60601-2-41; central illuminance in the tens of thousands of lux at 1 m	Lux meter at the stated working distance	Annually
Ambient room lighting	Typically 500–1,000 lux at the task plane	Lux meter grid	Annually
Downflow velocity under a UCV canopy	Commonly 0.25–0.45 m/s at 1 m above floor level	Anemometer grid beneath the canopy	Annually
Recovery time	100:1 particle recovery, commonly specified within 15–20 minutes	ISO 14644-3 recovery test	Annually
Microbial air count	Conventional theatre commonly ≤35 CFU/m³ in use; ultraclean zone ≤10 CFU/m³	Active air sampling plus settle plates, per the infection control committee’s written policy	Monthly to quarterly, per hospital policy
Noise	NC 35–45 with the theatre unoccupied	Sound level meter	At commissioning, and after plant changes

Three notes that prevent the most common arguments during an assessment.

Every measurement needs a stated occupancy state. A particle count taken in an empty, still theatre and a particle count taken during a live list are different tests with different results. If the certificate does not say “at rest” or “operational,” it is incomplete. This is covered in detail in ISO 14644 cleanroom classes explained for hospital operation theatres.

Every instrument needs a traceable calibration certificate within validity. An uncalibrated anemometer produces a number, not evidence. Assessors ask for the certificate of the instrument, not just the report it produced.

The measurement must be attributable. Who performed it, on what date, with what instrument, against what acceptance criterion, and who accepted the result. A report with a logo and a number and no signature is weak evidence.

Zoning, layout and flow

The four-zone cascade is the layout model most Indian OT complexes are designed around, and the one an assessor will mentally walk through.

Zone	Typical spaces	Pressure regime	Access control
Protective (outer)	Reception, trolley transfer bay, changing rooms, staff rest area, administration	Ambient or slightly positive to the outside	Open to hospital traffic; street footwear stops here
Clean	Pre-operative holding, clean corridor, sterile supply route, equipment and anaesthesia stores, PACU	Positive to protective zone	OT attire only
Sterile / aseptic	The operating room itself, scrub bay, sterile store, induction room where provided	Highest pressure in the cascade, positive to clean zone	Restricted; full OT attire, mask, controlled numbers
Disposal / dirty	Dirty utility, sluice, instrument washdown, waste holding, disposal corridor	Negative to all adjacent zones, separately exhausted	Restricted, one-directional

What an assessor is looking for underneath the diagram is separation of flows: patients in and out, staff in and out, sterile supplies in, and contaminated instruments and waste out, without those routes crossing where it matters. A single-corridor complex can comply — most Indian OT complexes are single-corridor — but only if it is supported by timing discipline, covered transport of contaminated items, and a written traffic policy that staff can describe.

The specific items to get right at design stage:

• Trolley transfer point at the protective/clean boundary, physically defined rather than notional.
• Scrub area sited so that scrubbed staff enter the theatre without passing back through a lower zone, with elbow, knee or sensor-operated taps, no hand-contact soap and antiseptic dispensers, and a drainage design that does not aerosolise.
• Sterile store inside the clean or sterile zone, positively pressured, temperature and humidity controlled, with closed shelving off the floor and away from walls, and no cardboard outer packaging crossing into it.
• Dirty utility with its own extract, a door that closes, and no shared route with sterile supply.
• Door count minimised. Every additional door is a leak in the pressure cascade and a discipline problem. Pass boxes exist so that doors do not have to open.
• Space to actually work. A major theatre in the region of 37–56 m² gives the clearances that infection control and equipment positioning need. Undersized theatres generate non-conformities indirectly — equipment stored in corridors, sterile trolleys parked in circulation space.

Surfaces, finishes and the envelope

The requirement is easy to state and hard to retrofit: the internal envelope must be seamless, non-porous, non-shedding, impact-resistant and able to withstand repeated disinfection without degrading.

• Walls and ceilings. Factory-finished panels, typically PPGI or SS304, with concealed fixings and flush joints. Antibacterial or antimicrobial surface finish. Ceilings continuous and sealed at every service penetration — light fittings, gas terminals, pendant boss plates, sprinkler heads and grilles are all penetrations, and each one is a potential finding.
• Junctions. Wall-to-wall, wall-to-floor and wall-to-ceiling junctions coved with a radius, not square. Square junctions collect and resist cleaning.
• Flooring. Seamless self-levelling epoxy or homogeneous welded vinyl, coved up the wall, with conductive or anti-static properties where specified. Chemical resistance to the disinfectants actually in use.
• Why tile and grout fails. Tiled theatres are still built in India because tile is cheap and familiar. The tile is not the problem; the grout is. Grout is porous, it absorbs disinfectant and organic matter, it cracks with thermal and structural movement, and there is no cleaning protocol that restores it. A tiled theatre generates a defensible finding on almost any careful inspection, and the only real remedy is replacement.
• Doors. Hermetically sealing, preferably automatic sliding with a hands-free actuator, with an airtight peripheral gasket, a clear opening wide enough for a bed with attached equipment, and a vision panel. Manual hinged doors pump air across the boundary every time they swing.
• Glazing. Flush-set laminated view panels, sealed on both faces, with no beading ledges.
• What quietly ruins a compliant envelope. Adhesive signage and tape on panels, screwed-on fixtures added after handover, cable trunking surface-run across a wall, a hole cut for a new device and never properly sealed, and silicone repairs that have shrunk and cracked. Put a rule in the OT policy that no penetration is made without engineering sign-off, and enforce it.

Medical gas and electrical inside OT scope

Medical gas. The theatre-side deliverables are a full terminal schedule per theatre — typically oxygen, nitrous oxide, 4-bar medical air, 7-bar surgical air, vacuum, AGSS and CO₂ where laparoscopy volumes justify it — mounted on pendants or wall units, all gas-specific and mechanically non-interchangeable. Each theatre or theatre group needs an Area Valve Service Unit sited outside the theatre where it can be reached without entering, and an area alarm panel visible to staff. The evidence pack behind it is the commissioning dossier: pressure and leak test records, 100% cross-connection and anti-confusion testing, particulate and purity results, and alarm function tests. Which standard that dossier should be built to is the subject of HTM 02-01 vs NFPA 99: which medical gas standard applies in India.

Electrical. Essential and non-essential circuits clearly segregated and labelled, UPS backing the surgical luminaire, monitors and anaesthesia machine with a stated and tested autonomy, equipotential bonding of all exposed metalwork with measured and recorded earth resistance, adequate socket provision at pendant and wall positions so that extension boards never appear, and — where specified for the patient vicinity — an isolated power supply with a line isolation monitor. Emergency lighting must actually illuminate the surgical field enough to close safely, and that should be demonstrated during a drill, not assumed.

The documentation set an assessor expects

This is where good theatres lose points. Assemble the following as a single OT compliance file, indexed, with every document dated and within validity.

Design and as-built

1. Design basis note stating the standards the theatre was designed to and the target values for every environmental parameter.
2. As-built architectural, HVAC, medical gas and electrical drawings for the OT complex, with zone and valve identification.
3. HVAC design calculations — air change rate, fresh air, heat load, pressure cascade.
4. Material and component certificates: panel specification, flooring, door assemblies, HEPA filter certificates to EN 1822 with individual filter serial numbers and scan test data.

Commissioning and validation

5. Air change rate validation report, per theatre.
6. Particle count / cleanliness classification report to ISO 14644-1, stating the occupancy state and the sampling plan used.
7. HEPA filter installed integrity (DOP/PAO scan) reports, per filter.
8. Pressure differential report across the full zone cascade, not just OT-to-corridor.
9. Temperature and humidity performance report.
10. Recovery test report.
11. Illumination measurement report — surgical field and ambient.
12. Medical gas commissioning dossier, including cross-connection and purity certificates.
13. Electrical safety report — earth resistance, insulation resistance, UPS changeover, LIM function where installed.
14. Microbiological baseline report before the theatre entered clinical use.

Ongoing operational records

15. Daily temperature, humidity and differential pressure logs, with defined action limits and evidence of escalation when breached.
16. HEPA and pre-filter replacement log with dates and filter serial numbers.
17. Periodic re-validation reports, at the interval your policy commits to.
18. Environmental surveillance results and the infection control committee’s review of them.
19. Calibration certificates for every instrument used to generate the above — thermometers, hygrometers, manometers, anemometers, particle counters, lux meters — from a laboratory with traceable calibration.
20. Preventive maintenance schedule and completed job cards for AHU, filters, doors, pendants, surgical lights, medical gas and UPS.
21. AMC contracts and evidence that the scheduled visits actually happened.
22. Fumigation or terminal cleaning records, with the agent, method and contact time recorded.
23. Downtime and breakdown register with response and closure times.
24. OT utilisation, cancellation and turnaround records.
25. Staff training records: fire, medical gas shutdown, spill management, infection control, equipment-specific competency.
26. Surgical safety checklist audit, counts audit and SSI surveillance data with trend analysis.

Two structural points. First, a preventive maintenance schedule with no completed job cards is worse than no schedule, because it documents your own non-compliance. Second, calibration is the most common single gap: hospitals hold the reports but not the calibration certificates of the instruments that produced them, and once that is pointed out the reports carry very little weight.

Pre-audit checklist

Work through this in the four weeks before an assessment. Anything you cannot answer with a document in hand is a finding waiting to happen.

Environment

• Every theatre has a validation report dated within the interval your own policy states.
• Every report names the occupancy state and the acceptance criterion, not just a result.
• Differential pressure is displayed at each theatre door and the gauge reads within range right now.
• Temperature and humidity logs are complete for twelve months with no blank days.
• Out-of-range entries have a recorded action and a closure.
• Filter replacement log matches the filter serial numbers physically installed.
• Every measuring instrument has a valid, traceable calibration certificate.

Fabric

• No visible joint failure, silicone cracking, panel damage or unsealed penetration.
• No tape, adhesive posters or unapproved fixings on panels.
• Coving intact at all junctions; no lifting or cracking of flooring.
• Doors close fully and seal; automatic doors respond to the hands-free actuator.
• Pass boxes functional and interlocks working.
• No storage in corridors; nothing stored on the floor in the sterile store.

Services

• AVSU accessible, labelled with the areas it serves, and staff can identify it.
• Area gas alarm panel functional and tested within the cycle.
• Gas purity re-test certificate current.
• UPS autonomy tested and recorded; battery replacement dates known.
• Earth continuity and resistance re-tested within the cycle.
• Emergency lighting tested with the theatre in a realistic configuration.

Process

• Written OT policy covering traffic, attire, cleaning, scheduling of infected cases and terminal cleaning — and staff practice matches it.
• Surgical safety checklist completed and audited, with the audit showing something other than 100%.
• Counts policy and completed count records.
• Credentialing and privileging file current for every operating consultant.
• Biomedical waste segregation correct at the point of generation, not corrected later.
• Fire exit route from the OT complex unobstructed; staff can describe the evacuation plan.
• Mock drill records for fire and for medical gas failure.

Common non-conformities and how to avoid them

Non-conformity	Root cause	Prevention
Validation report older than the stated policy interval	No calendar owner for re-validation	Put re-validation into the AMC scope with fixed dates, not on request
Particle count with no occupancy state declared	Test agency using a generic template	Specify the occupancy state and the sampling plan in the purchase order for the test
Uncalibrated test instruments	Calibration tracked for clinical equipment only	Add every measurement instrument to the same calibration register as clinical devices
Differential pressure gauge reading zero or unreadable	Gauge never commissioned or tubing disconnected	Verify each gauge physically during monthly rounds and log the reading
Grout lines, cracked coving, unsealed penetrations	Tiled construction, or post-handover modifications	Seamless finishes at build; a written no-unauthorised-penetration rule afterwards
Doors propped open during a list	Workflow forces it — supplies or equipment outside the theatre	Fix the workflow: pass boxes, correct stock levels, sited equipment stores
PM schedule exists, job cards missing	Verbal maintenance culture	Job card signed and filed on the same visit, or the visit did not happen
Sterile store crowded, stock on the floor	Store undersized at design stage	Size the sterile store to actual consumable turnover, and enforce shelving standards
Staff cannot locate the zone valve	Training done once at handover	Repeat drills; put a valve location diagram at the nursing station
Surgical safety checklist 100% compliant on paper	Retrospective completion	Audit by observation, not by chart review, and expect the number to drop
Gas outlet delivering the wrong gas after a modification	Post-handover work with no re-test	Any intervention on live pipework requires a permit to work and re-certification of the affected zone

The pattern across that table is that infrastructure failures are mostly design-stage decisions and documentation failures are mostly ownership failures. Neither is fixed in the month before an assessment, which is the argument for treating the compliance file as a live system rather than an event.

Related reading

• ISO 14644 Cleanroom Classes Explained for Hospital Operation Theatres — what ISO Class 5 and Class 7 actually mean, the old Class 100 / 10,000 translation, and why at-rest and operational results differ.
• HTM 02-01 vs NFPA 99: Which Medical Gas Standard Applies in India? — how to specify a medical gas system that survives an audit.
• Modular Operation Theatre — turnkey OT scope, components and the validation package delivered at handover.

Preparing a theatre complex for an assessment cycle, or building one that has to clear it first time? Request a compliance-scoped assessment and we will map your design and your evidence file against the standard you are being assessed to.