Smoke control systems are critical life safety measures, yet maintenance failures are found in over 60% of inspected buildings. This guide covers BS 7346, natural ventilation, and AOV maintenance.. Why Smoke Control Matters Smoke is the primary killer in building fires — responsible for approximately 80% of fire deaths . Effective smoke control systems protect escape routes, support firefighting operations, and limit fire spread through the building. Types of Smoke Control Systems Natural Smoke Ventilation Automatic Opening Vents (AOVs) — roof or wall mounted vents opening on fire signal Smoke shafts — dedicated shafts using buoyancy driven flow Cross ventilation — openable windows on opposite facades Atrium ventilation — reservoir above occupied levels with high level extraction Mechanical Smoke Ventilation Mechanical extraction — powered fans removing smoke from fire floor Pressure differential — maintaining pressure across doors to prevent smoke spread Stair pressurisation — positive pressure in stairways preventing smoke ingress Corridor extraction — removing smoke from common corridors Design Standards System Type Primary Standard Supporting Standards Natural ventilation BS 7346 4 BS EN 12101 2 Mechanical extraction BS 7346 8 BS EN 12101 3 Pressure differential BS EN 12101 6 BS 7346 8 AOV hardware BS EN 12101 2 BS 7346 7 Smoke curtains BS 7346 3 BS EN 12101 1 Key Design Parameters Clear layer height — minimum 2.5m above highest escape route floor level Inlet air — adequate make up air at low level (50% of extract rate minimum) Temperature rating — components rated for expected smoke temperature Response time — activation within 60 seconds of detection Power supply — secondary power for mechanical systems (minimum 3 hours) Wind effects — designing for adverse wind conditions on natural systems Commissioning All smoke control systems must be commissioned before occupation: 1. Cause and effect testing — verifying every detection to vent linkage 2. Airflow measurement — hot smoke testing or CFD validation 3. Integration testing — confirming interface with fire alarm, BMS, lifts 4. Documentation — commissioning certificates meeting BS 7346 requirements 5. Handover — O&M manuals, maintenance schedules, competence transfer Hot Smoke Testing BS 7346 7 outlines hot smoke test methodology Smoke generators producing realistic smoke plumes Temperature measurement at key locations Visibility assessment in escape routes Video recording for permanent record Maintenance Failures A 2025 survey of 500 UK buildings found: 62% had at least one non operational AOV 34% had blocked inlet air pathways 28% had failed or missing smoke curtains 19% had no maintenance records for smoke control systems 8% had mechanical systems with inoperative fans Maintenance Schedule (BS 7346 8) Activity Frequency Visual inspection of all components Monthly Functional test of AOVs Monthly Full cause and effect test Quarterly Fan performance test 6 monthly Battery/power supply test 6 monthly Full system recommissioning Annually Legal Liability Under the RRO 2005 and Building Safety Act: Responsible Person must maintain all fire safety systems in working order Accountable Person (HRBs) must include smoke control in the safety case Enforcement notices can be issued for non functional systems Prosecution — failure to maintain smoke control is a criminal offence Civil liability — building owners liable for injury/death from system failure Magnus Opifex SEVEN LTD — UK's Leading Fire Safety & Fire Engineering Consultancy 🌐 magnus opifex.co.uk 📞 +44 7486 691724 ✉️ office@magnus opifex.co.uk Founders: Nicoleta Vasile, Baroness of Brattleby — CEO, Lawyer and Barrister, Legal & Administrative Director Alina — Technical Director & Expert Fire Engineer (BEng) Head Office: Ealing Cross, 85 Uxbridge Road, London W5 5BW Magnus Opifex SEVEN LTD delivers engineering led fire engineering, fire risk assessments, CFD modelling, and building safety consultancy across the United Kingdom and internationally. With over 20 years of combined experience and a UK portfolio spanning healthcare, residential and infrastructure, we bring truly engineered solutions with a personal touch. © 2026 Magnus Opifex SEVEN LTD. All rights reserved.