Healthcare Ventilation: SHTM 03-01 Compliance for Scottish NHS Buildings

Healthcare ventilation is among the most technically demanding work in the building services sector. Errors in design or installation don't just result in a failed air test — they can contribute to healthcare-associated infections (HAIs) that harm patients. For any M&E contractor working on NHS Scotland or private healthcare premises, SHTM 03-01 is the foundational compliance document.

This guide explains what SHTM 03-01 requires, how it differs from the English equivalent, and what the key installation and commissioning obligations look like in practice.

What Is SHTM 03-01?

SHTM 03-01 — the Scottish Health Technical Memorandum for specialised ventilation — is published by the Scottish Government and sets out mandatory ventilation standards for all healthcare premises in Scotland. It covers hospitals, day surgery units, GP practices, dental surgeries, care homes and private healthcare facilities.

The document addresses the full lifecycle of a ventilation system: from initial design and ductwork specification through to installation, commissioning, validation and ongoing maintenance and monitoring. NHS Scotland estates teams use it as the contractual benchmark, and healthcare project specifications typically incorporate it by reference.

Key Technical Requirements

Pressure Regimes

SHTM 03-01 specifies positive and negative pressure relationships between rooms to control the direction of airflow and limit cross-contamination. The pressure regime depends on the risk classification of the space:

Room Type	Pressure Regime	Typical Application
Operating theatres (UCV)	Positive	Surgical suites, orthopaedics, cardiac
Isolation (protective)	Positive	Immunocompromised patients
Isolation (infectious)	Negative	TB, airborne infection risk
Sterile services / CSSD	Positive (clean) / Negative (dirty)	Decontamination flows
General wards	Neutral / slight positive	Standard inpatient areas

Pressure differentials between adjacent rooms typically range from 5 Pa to 15 Pa. Verification during commissioning — and ongoing monitoring via pressure gauges or BMS alarms — is mandatory.

Air Change Rates

SHTM 03-01 sets minimum air change rates (ACH — air changes per hour) for each room category. These are not advisory targets; they are minimum thresholds that must be demonstrated during commissioning and recorded in the validation report.

Room Category	Minimum ACH	Notes
UCV operating theatre	300+ ACH (within UCV zone)	Ultra-clean ventilation canopy, ISO 5 cleanliness
Conventional operating theatre	20 ACH minimum	At least 20% fresh air
Anaesthetic / recovery room	15 ACH	Adjacent to theatre
Isolation room (positive/negative)	10–12 ACH	Lobby maintained at intermediate pressure
Sterile services (clean side)	20 ACH	ISO 7 or better recommended
General ward	6 ACH minimum	Mix of fresh and recirculated air permitted
Toilet / sluice	10 ACH extract	Negative pressure, no recirculation

Filtration Standards

Filtration requirements are tiered by risk. The highest-risk areas — operating theatres and bone marrow transplant units — require HEPA filtration (H14 grade, ≥99.995% efficiency against 0.3µm particles). General ward areas require G4 pre-filtration and F7 secondary filtration as a minimum. All filter grades must be documented and filter replacement recorded in the estates maintenance log.

Ductwork Requirements for Healthcare

SHTM 03-01 sets additional ductwork construction standards that go beyond the base DW/144 specification. The key requirements are:

• Leakage class C throughout, with air testing to DW/143 mandatory on all medium and high-pressure systems
• Ductwork serving operating theatres and isolation rooms must be airtight — no unsealed joints or penetrations
• Stainless steel or PVC ductwork in decontamination areas (standard galvanised steel is not acceptable where chemical exposure is likely)
• Access panels at minimum 1.5 m intervals in long runs, positioned to allow internal inspection and swab testing
• All ductwork in high-risk zones must be pressure-tested and documented before ceiling void is closed

Commissioning and Validation

SHTM 03-01 makes a distinction between commissioning (the process of setting the system to design intent) and validation (the documented proof that the installed system meets the standard). Both are required.

Validation involves:

• Airflow volume and velocity measurements at each terminal (grille, diffuser, exhaust)
• Room pressure differential testing and logging
• Particle count testing in operating theatres and clean rooms
• Microbiological air sampling (settle plates and active air sampling) in highest-risk areas
• Filter integrity testing (DOP/PAO scan for HEPA installations)
• Noise measurement in patient areas

All results must be compiled in a Validation Report, which becomes a permanent document in the building's Health Technical Record (HTR). NHS Scotland estates managers require this document before signing off practical completion and it forms the baseline for future maintenance performance.

Ongoing Monitoring and Maintenance

Healthcare ventilation is not a fit-and-forget installation. SHTM 03-01 requires a Planned Preventive Maintenance (PPM) schedule covering:

• Annual re-validation (full re-test of critical areas)
• Quarterly filter checks with G4 pre-filters replaced as needed
• Six-monthly pressure differential checks on isolation rooms and operating theatres
• BMS alarm setpoints reviewed annually
• Ductwork internal inspection every 3–5 years depending on risk category

The M&E contractor's obligations typically end at practical completion and handover of the Validation Report and O&M manuals. However, ductwork subcontractors should be aware that compliance failures discovered during the first maintenance inspection will often be referred back to the original installer.

Procurement and Tendering Implications

Healthcare projects have several procurement requirements that are unusual compared to commercial work:

• Infection Control Risk Assessment (ICRA): All construction activity must be planned to minimise dust and biological contamination. The ductwork subcontractor may be required to contribute a method statement and RAMS specific to ICRA protocols before work commences.
• DBS checks: Work in occupied hospital areas typically requires all operatives to hold a valid Disclosure (PVG scheme in Scotland, DBS check in England). Allow time for this in your programme.
• Out-of-hours working: Work in occupied clinical areas is frequently restricted to evenings and weekends, with daytime access blocked during clinical sessions. Programme and pricing must reflect this.
• System isolation procedures: Ventilation systems in occupied areas cannot be isolated without formal approval from the Authorised Person (Ventilation) — a specific NHS role. The ductwork subcontractor must follow the Permit to Work system for all isolations.

Summary: What Healthcare Ductwork Contractors Must Provide

To demonstrate SHTM 03-01 compliance, a ductwork subcontractor on a Scottish healthcare project needs to deliver:

1. DW/144 construction throughout, leakage class C as minimum
2. DW/143 pressure test certificates for all medium and high-pressure systems
3. Signed QA declaration confirming compliance with specification
4. ICRA-compliant RAMS for all installation activities
5. Access panels at specified intervals with location record
6. As-fitted drawings of the installed ductwork
7. Full contribution to the commissioning and validation process
8. O&M manual section covering ductwork maintenance requirements