Presentation on theme: "Smoke shafts vs pressurisation Colt Technical Seminar Paul Compton Technical Director."— Presentation transcript:
Smoke shafts vs pressurisation Colt Technical Seminar Paul Compton Technical Director
“I J O’Hea. Colt Founder” I J O’Hea OBE ( ) 2013 Group Turnover £152 million Manufactures in the Brazil, China, the Netherlands, Saudi Arabia, the UK and the USA Private Company founded in 1931 A brief history of Colt
Current UK Business markets Environmental Comfort Control Natural Ventilation Louvre Solar Shading Smoke Control
Smoke shafts vs pressurisation
1.What do these systems do? 2.Legal basis and standards: 3.Relative benefits, performance, space and cost 4.Compensation for non-compliant layouts - Extended Travel Distances etc 5.Which system should I choose? Covering:
Protect stairs from smoke ingress to aid safe evacuation to aid safe fire fighting access Reduce smoke ingress to lobbies or corridors adjoining stairs Reduce risk of smoke spread via lifts Protect fire fighting or evacuation lifts from smoke ingress Design basis is always a single fire, not located in the stair, lobby or lift. What do these systems do?
Legislation In the UK the relevant legislation is Building Regulations and their associated guidance documents (Approved Document B in England and Wales and its equivalents in Scotland and Ireland). In ADB: Smoke control is recommended, directly or by reference to BS 5588 in: - Residential escape stairs - All fire fighting stairs - AOV, natural shafts and pressure differential systems are largely treated as equivalents - mechanical shafts are not discussed (too new) - pressurisation can also be added to avoid discounting a stair or adding lobbies in commercial buildings Legislation and standards
Standards In the UK we have: BS 5588 (withdrawn) BS 9991 BS 9999 BS 9991 and BS 9999 recommend a pressure differential system if a building has a floor more than 30m above ground level. BS EN is the design standard for pressure differential systems Legislation and standards
BS EN Sets requirements for 6 different classes of system. Only 2 are commonly used: A & B. Legislation and standards Closed Door RequirementsOpen Door Requirement ClassStair (Pa) Lift Shaft (Pa) Lobby (Pa) Velocity (m/s) Open Doors A5050*45*0.75 Stair door on fire floor B Stair door on fire floor Stair door on floor below Lobby door on fire floor Lift door on floor below Final exit door * = If pressurised
Do mechanical smoke shafts provide depressurisation to BS EN ? The standard was not written with this in mind 50Pa? 0.75m/s? 100N? Standby fans? Conclusion: No, but it does match some requirements. Legislation and standards
Performance comparison Accommodation air release ventilator Smoke detector Pressure relief damper FIRE FLOOR Stairs Ground floor First floor 2 m/s average velocity Lift door open
Performance comparison Mechanical smoke shaftPressurisation Stair: Kept smoke free Lobby: Likely to be smoky for limited periods Lobby: Kept smoke free if pressurised, otherwise likely to be smoky for limited periods Lifts: Usually protected from smoke entry by light depressurisation of lobby Lifts: Kept smoke free if lift or lobbies pressurised. Otherwise not specifically protected
A mechanical shaft system needs a single shaft, typically 0.5m 2 to 1m 2 cross section. A pressurisation system needs: A shaft for each area pressurised, typically 0.15m 2 to 2.0m 2 Accommodation air release (another shaft?) Space requirements (shafts) + + Lobbies StairLobbies?Lift?
Space requirements (roof)
Difficulties and issues – smoke shafts negative Fire Fighting Lobby Staircase Excess depressurisation Large doors Basement stair air inlet
Difficulties and issues – pressurisation Large doors Quality of building construction Accommodation Air Release
You get what you pay for. Pressurisation can provide the best protection but is the most expensive. A mechanical shaft is next best and next most expensive. A natural shaft is less expensive (but takes up more valuable space). AOV are low cost but provide the least good protection. Costs
Non-ADB compliant buildings Extended travel distances in residential buildings
It’s not uncommon for older buildings to be unable to comply with current layout requirements (number of stairs, lobbies, etc). Pressurisation? Alternatives? Non-ADB compliant buildings Refurbishment / change of use
There’s no hard and fast answer, but this table might help guide you. Which system do I choose? Taller than 30m?If following BS 9991 or BS 9999, pressurisation is recommended. Space is tight?A mechanical shaft system is normally most space efficient (if AOVs not suitable). Budget is tight?Natural ventilation is the low cost option if practical. To avoid lobbies or discounting a stair Pressurisation. For extended travel distances An enhanced mechanical shaft system is essential.