Pressurisation Systems Technical Seminar
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Pressurisation Systems in residential and commercial buildings Pressurisation Systems CPD Approved Document B to the Building Regulations requires smoke ventilation to escape stairs and, under some circumstances, common lobbies and/or corridors in residential buildings. Pressurisation is one way of meeting this requirement. This seminar covers: An explanation of the basic legislative requirements and how these are achieved The various design approaches Specifying the equipment
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Pressurisation Systems Technical Seminar
- 1. Pressurisation Systems Colt Technical Seminar
- 2. “I J O’Hea. Colt Founder” I J O’Hea OBE (1897 - 1984) 2009 Group Turnover £170 million Manufactures in the UK, Holland, Saudi Arabia, China and Singapore Private Company founded in 1931 A brief history of Colt
- 3. Current UK Business markets Solar Shading Natural Ventilation Louvre Environmental Comfort Control Smoke Control
- 5. WHY PRESSURISE? • Approved Document B to the Building Regulations requires smoke ventilation to escape stairs and, under some circumstances, common lobbies and/or corridors in residential buildings. • Pressurisation is one way of meeting this requirement • Alternatives to pressurisation are: – Natural AOV’s – Natural Shafts – Mechanical ColtShaft
- 6. • Alternative to natural ventilation when escape stairs or fire fighting stairs are landlocked • A requirement for some fire fighting stairs • Provides much better protection than natural ventilation of stairs • Note: BRE shaft and Colt Shaft have significantly reduced the market for pressurisation of fire fighting stairs • Pressurisation systems should conform to the requirements of EN 12101-6:2005 WHY PRESSURISE?
- 7. BS 9999: 2008 recommends Pressurisation (designed to EN12101-6) to: • Replace separation of dead end corridors with a fire door • Replace protected lobbies in single stair buildings, buildings over 18m, buildings with phased evacuation and buildings where a stair has not been discounted in the sizing of escape widths • Allow a single stair to extend down to a basement • fire fighting shafts over 10m deep and over 30m tall (Class B) WHY PRESSURISE?
- 8. West India Quay, London Oxford Road, Leicester INSTALLATIONS
- 9. Beetham Tower, Birmingham Holiday Inn Express, Hull INSTALLATIONS
- 10. System Class Application Typical Building Type A Means of Escape Defend in Place Residential B MoE and Fire fighting Where fire fighting core is required C MoE Simultaneous Evac. Commercial D MoE Sleeping Risk Hotels/Hospitals E MoE Phased Evacuation High rise offices EN 12101- 6 BUILDING CLASSIFICATION
- 11. BASIC PRINCIPLES • The system must protect against smoke entering the stairs or travelling between storeys via lifts accessed from protected lobbies • The intent is to have the highest pressure in the stairs and a reducing pressure gradient through to the accommodation • All ‘pressures’ described are actually pressure differentials to the accommodation
- 12. BASIC PRINCIPLES • All pressurisation systems require 3 basic components: • A means of supplying clean air to pressurised areas • A means of ensuring excessive pressure differentials do not occur • A means of relieving pressure from the accommodation
- 13. WHICH AREAS DO WE PRESSURISE? The first decision to make for any system • Depends upon class of pressurisation • Depends upon building layout – Is there a lift? – Where is suitable for accommodation air release
- 14. STAIRS (WITH SIMPLE LOBBY) Pressurise the stairs only. Only used where the staircase is entered via a simple lobby (i.e. a lobby without lifts or other possible escape route) or directly from the accommodation. Accommodation Stairs Simple lobby Air supply +ve
- 15. STAIRS, LOBBY & LIFT Pressurise stairs and lobbies. Used to extend protection to lobbies: Stairs Lift Accommodation Air supply +ve +ve
- 16. STAIRS, LOBBY & LIFT Pressurise stairs, lobby and lift. Generally only used in fire fighting – Class B Stairs Lift Accommodation Air supply +ve +ve +ve Lobby
- 17. WHAT PERFORMANCE IS REQUIRED? Depending upon the class of system we have set criteria to achieve: • Pressure differentials – all doors closed: 45 – 50 Pa • Velocity through open door on fire floor: 0.75 – 2.0 m/s • Pressure differential – doors open on floors other than fire floor: 10 Pa
- 18. CLASS A - DOORS CLOSED Automatic air release ventilator Smoke detector Pressure relief damperDuty /standby fan Ductwork system FIRE FLOOR (LOBBY/CORR) Stairs 50Pa (above accomm odation) Ground floor First floor Door opening force not to exceed 100N
- 19. CLASS A - DOOR OPEN Accommodation air release ventilator Smoke detector Pressure relief damperDuty /standby fan Ductwork system FIRE FLOOR (LOBBY/CORR) Stairs Ground floor First floor 0.75 m/s average velocity
- 20. CLASS A: MoE - Defend in Place • Do not attempt to pressurise the corridors up to dwelling front doors • Provide air release from the corridor or lobby • Long corridors will be fitted with smoke seal doors - air release needs to be on stairs side of nearest doors
- 21. CLASS A Air release via ventilator Air release via shaft Accommodation CLASS A
- 22. CLASS B: FIRE FIGHTING STAIRS • Requirement for stairs set by ADB BS 5588-5 or BS 9999 • Pressurised lobbies essential • Lobbies may contain fire fighting lift, which also needs to be pressurised
- 23. CLASS B - DOORS CLOSED Accommodation air release ventilator Smoke detector Pressure relief damperDuty /standby fan Ductwork system FIRE FLOOR Stairs Ground floor First floor 50 Pa above accomm odation 45 Pa above accomm odation Supply to stair, lift and lobby Door opening force not to exceed 100N
- 24. CLASS B - DOORS OPEN Accommodation air release ventilator Smoke detector Pressure relief damperDuty /standby fan Ductwork system FIRE FLOOR Stairs Ground floor First floor 2 m/s average velocity Lift door open if fitted
- 25. Closed Door Requirements Open Door Requirement Class Stair (Pa) Lift Shaft (Pa) Lobby (Pa) Velocity (m/s) Open Doors A 50 50* 45* 0.75 Stair door on fire floor B 50 50 45 2.0 Stair door on fire floor Stair door on floor below Lobby door on fire floor Lift door on floor below Final exit door C 50 50* 45* 0.75 Stair door on fire floor + 10Pa pressure difference with final exit door open only D 50 50* 45* 0.75 Stair door on fire floor and final exit door + 10 Pa pressure difference with final exit door open and one stair door other than the fire floor E 50 50* 45* 0.75 Stair door on fire floor and another floor and final exit door + 10 Pa pressure difference with final exit door and two stair doors open other than the fire floor * Pressurising these spaces is at the discretion of the system designer
- 26. CLASS C - DOORS CLOSED Accommodation air release ventilator Smoke detector Pressure relief damperDuty /standby fan Ductwork system FIRE FLOOR Stairs 50Pa above accomm odation Ground floor First floor Door opening force not to exceed 100N
- 27. CLASS C – EXIT DOOR OPEN Accommodation aor release ventilator Smoke detector Pressure relief damperDuty /standby fan Ductwork system FIRE FLOOR Stairs Ground floor First floor 10 Pa above accomm odation
- 28. Accommodation air release ventilator Smoke detector Pressure relief damperDuty /standby fan Ductwork system FIRE FLOOR Stairs Ground floor First floor 0.75 m/s average velocity CLASS C - DOOR OPEN
- 29. EQUIPMENT • Fans – ambient rated – duty + standby (or standby motor) if only one MOE route; usually in series to save space – One fan set may supply stairs, lobbies and lift shaft – not usually attenuated unless needed for test periods – In 1 hour fire rated enclosure or roof • Power supplies – primary + secondary – Mains + generator or separate mains supply • Pressure relief – usually gravity damper in stair – inverter control of fans possible but difficult due to response speed requirement
- 30. EQUIPMENT • Ductwork – separate vertical ducts for stair, lobbies, lift shaft – ambient rated unless breaching fire compartmentation – Builders work shafts are suitable if well sealed – VCD required at each tee and grille for balancing – Two separate inlets facing different directions with smoke detector operated inlet dampers if at roof level – 5m away from any smoke exhaust • Grilles – one per 3 storeys in stair – one per lobby – one per 30m in lift shaft
- 31. EQUIPMENT Twin air intakes on separate facades of the building with motorised dampers and smoke detector control Volume control dampers on each section of ducting
- 32. EQUIPMENT • Accommodation air release – by leakage, ventilators, natural or mechanical shaft – leakage can be from building fabric, HVAC ductwork, permanent trickle vents, but not window breakage – ventilators must be provided on at least 2 sides, discount the side with the largest vent area (2.5m/s) – Natural shaft terminations need to be located to minimise adverse wind effects (2m/s) – Mechanical shafts should operate whenever the pressurisation system does and should not cause excess pressure differentials
- 33. CONTROLS • Initiation – From automatic fire detection system – Needs to identify fire floor – Locate detector close to door to pressurised space • Class B initiation – Can be manual switch from MOE state or direct from automatic fire detection system • Accommodation air release – only opened on fire floor (to prevent risk of fire/smoke spread) • Fire fighter controls – provided at base of stair
- 34. BASIC PRINCIPLE • Pump air into a ball or a tyre and we have a positive pressure inside • If there is a puncture then to maintain a positive pressure we need to keep pumping air in • For a given pressure and a given puncture size we will require a fixed rate of air input to balance the air lost through the puncture
- 35. BASIC PRINCIPLE • From Bernoulli’s equation: • ∆P = 0.5 ρ ∑ ( Q2 /A2 ) • Rewriting and correcting for effective area • Q = 0.83 ∑ (A ∆P0.5 ) • Q is the leakage rate from the pressurised space that we need to balance with supply air
- 36. BASIC PRINCIPLE • Easy in principle but we have a complex network of leaks and conditions to fulfil • Therefore the calculation becomes complex • EN 12101-6 devotes a 12 page annex to this
- 37. DUCT SIZING • Select duct layout and dimensions • Calculate resistance of ductwork • The operating pressure of the system should be added to the ductwork resistance • Size fans to provide the design flow rate at the total pressure
- 38. PROBLEMS Design process requires: – an assessment of the build quality and an allowance for additional unidentified leakage – this is in effect a ‘guess’ – Loose, average or tight construction will affect the leakage rates used in calculation – add 50% safety margin + 15% margin for duct leakage + 20% duct pressure loss margin There is often a temptation to reduce the allowances at design stage – this can lead to problems at completion of the project when pressures/velocities cannot be achieved.
- 39. COMMISSIONING 1. Check equipment is installed as per design 2. Carry out normal mechanical and electrical checks 3. Carry out performance tests, but first: • All doors must be fitted and close properly • All finishes must be complete - carpets laid etc • All false ceilings must be in place • There must be no temporary openings or unsealed service penetrations
- 40. EQUIPMENT CHECKLIST - Main power supply and standby supply - Duty and standby fan - Automatic change over - Fan located in protected area - Fan Inlet protected from effects of smoke - Smoke detection provided adjacent to lobby/accommodation door - Manual override provided - Supply point located at every 3 floor levels - Pressure relief damper provided in stair - Venting provided from accommodation - No smoke seals provided on doors
- 41. PERFORMANCE TESTING • While the test method aims to neutralise the effects of wind, testing on windy (and especially blustery) days should be avoided if possible • A pre-test inspection is recommended to identify potential problems that can be rectified prior to actual test • Out of hours testing is highly recommended • On day of test, ensure all other H&V systems are shut down
- 42. MEASUREMENT TECHNIQUES • PRESSURE DIFFERENTIAL • Requires a manometer and 2 long flexible tubes • Locate end of one tube in the accommodation and the other in the pressurised space, both away from draughts and at least 50mm above floor • Manometer then reads pressure differential directly 51
- 43. PERFORMANCE TESTING Pressures • On each floor in turn open all doors, allow them to close and then measure the pressure differential across each relevant door • Measure the opening force required on each relevant door at the door handle
- 44. MEASUREMENT TECHNIQUESAIR VELOCITY • Requires a rotating vane anemometer • Standing to one side (out of air stream) place anemometer in the plane of the door • Measure flow rate at 8 locations spread evenly • Do not move the anemometer during readings • Take arithmetic average of readings
- 45. PERFORMANCE TESTING Velocities • On each floor in turn open doors as specified in EN 12101-6 and measure average air velocity • For classes C, D, E on each floor in turn open doors as specified in EN 12101-6 and measure pressure differential between stair and accommodation • Adjust system as necessary and retest until all pressures and velocities are correct
- 46. PERFORMANCE TESTING • The procedure is simple, but in practice: – Excessive leakage is often a problem and can lead to a need for multiple commissioning visits and arguments with the builder – Testing and balancing large systems can be very time consuming, especially with pressurised lobbies
- 47. THE FUTURE • A CEN committee is currently revising EN 12101-6 • Proposals are: – Delete ‘kit’ references and CE marking – Simplify system requirements – Reduce costs – Not likely to be published until 2011
Notas del editor
- Smoke control is Colt’s largest market sector in the UK and Colt have been involved in the development of smoke control since we installed the UK’s first modern industrial smoke ventilation system in the mid 1950s.
- By investing in innovation, products, services and people, Colt International has established itself as an international leader in the fields of: Smoke Control Solar Shading Natural Ventilation Louvre Environmental Comfort Control (HVAC) Air Handling Systems
- This second part of the seminar will look at the development of shaft ventilation for protection of common escape routes, particularly in high rise residential buildings.
- Pressurisation can be used for various applications, although in a lot of cases there are a number of options available to designers
- While these other methods often meet the requirements of the building codes, none of these are quite as effective as pressurisation for keeping a space smoke free. Where pressurisation is selected, it should be designed to the EN standard
- The latest fire safety standard, BS 9999 also refers to pressurisation for specific applications
- Colt have experience in the design of systems for all varieties of buildings from apartments to high rise offices
- To fire fighting stairs to basements and hotels
- Press. Systems are classified into 5 groups, each with different design criteria, depending on the risk/application
- Press. Systems work by maintaining a higher ‘differential’ pressure in the protected space than in the surrounding spaces where fires could possibly occur. The pressures achieved are all relative to the reference point, that is, the room containing the fire.
- Press. Systems must have a means of getting clean air into the building, a means of preventing too much pressure occurring and a means of getting the air out of the unpressurised space.
- The class of press. System will depend on the type of building, the buildings use, the type of stair to be pressurised and why it is being pressurised.
- The simplest systems require only the staircase to be pressurised. In which case, air is supplied direct into the staircase and allowed to leak from the adjacent lobby
- Where the layout is more complex it may be necessary to supply air to both the stair and the lobby.
- Fire fighting cores will usually contain a protected stair, protected lobby and fire fighting lift – all 3 need pressurising the lobby should be slightly lower than the stairs and lift.
- The different classifications of system have different criteria to meet, but the basic requirements are a pressure differential in the stair/lobby/lift and a velocity through the door when open to the accommodation space. The different classifications will specify what pressures/velocities should be achieved when certain doors or combinations of doors are open/closed
- Class A should achieve 50Pa in the staircase when all the stair doors are closed. the door opening force should not exceed 100N – this is of particular importance to doors opening into the pressurised space.
- When the door to the accommodation is open, the system should achieve an average velocity of 0.75m/s across the door
- Class A applies to residential buildings, but the air relief path cannot be through the occupants apartment – this would rely on the owner of the apartment maintaining components of the system and not tampering with them. The air relief system must be kept in common areas.
- Where an outside wall is available, a natural vent can be used, although to comply with the standard completely, this should be on two separate facades. Alternatively a common shaft system may be used.
- A fire fighting stair has the most onerous design criteria and all associated areas must be protected.
- When all doors are closed, the system must achieve 50Pa in the staircase and lift and 45Pa in the lobby, relative to the accommodation rooms. In addition, the door opening force should not exceed 100N – this is of particular importance to doors opening into the pressurised space.
- In the open door condition, the system must achieve an average velocity of 2m/s across the door into the accommodation space with the lobby door and stair door open on the fire floor, the stair door and the lift door open on the floor below and the final exit door open at the bottom of the staircase. If the stair has a lobby at the fire service access level and an external rising main inlet point, then this final open door may be discounted
- In the open door condition, the system must achieve an average velocity of 2m/s across the door into the accommodation space with the lobby door and stair door open on the fire floor, the stair door and the lift door open on the floor below and the final exit door open at the bottom of the staircase. If the stair has a lobby at the fire service access level and an external rising main inlet point, then this final open door may be discounted
- Class C applies to commercial buildings and should achieve 50Pa in the staircase when all the stair doors are closed. Door opening force should again not exceed 100N
- When the final exit door is open, the pressure in the stair should be at least 10 Pa above the accommodation space
- When the door to the fire floor only is open, an average velocity of 0.75m/s must be achieved across the door.
- Class D applies to buildings where occupants may be asleep, e.g. hotels. System should achieve 50Pa in the staircase when all the stair doors are closed. Door opening force should again not exceed 100N
- When the final exit door is open, the pressure in the stair should be at least 10 Pa above the accommodation space
- When the both the final exit door and the door to the fire floor only is open, an average velocity of 0.75m/s must be achieved across the door.
- Class E applies to buildings designed with phased evacuation, i.e. where the building is not all evacuated at once. System should achieve 50Pa in the staircase when all the stair doors are closed. Door opening force should again not exceed 100N
- System should achieve 10Pa between stair and fire floor when doors on two floors remote from the fire floor, plus the final exit door are open
- In the open door condition, the system must achieve an average velocity of 0.75m/s across the door into the accommodation space with the stair door open on the fire floor, the stair door on another floor and the final exit door open at the bottom of the staircase.
- Run and standby fans are required along with standby power supplies – pressure relief is required in the staircase to relieve excess air between the door open and door closed scenarios. EN 12101-6 has a stringent limitation on the response time of the system which makes the use of inverters very difficult although in some instances, there is little choice.
- If multiple pressurised spaces are required e.g. stair/lobby/lift, there should be separate ducts serving each. For systems being fed from high level, two inlets are required, facing onto differing facades of the building, with a smoke detector on the primary intake. If smoke is detected. The primary should close and hopefully the other intake will be on a smoke free façade. For systems fed at low level, only one intake is required – if smoke is detected, then the whole system shuts down. It is advisable to provide VCDS on every supply duct and at each branch/level, to make the system as flexible as possible for balancing purposes. The staircase should have input grilles on every third level.
- Accommodation air release is required to keep the fire floor at a neutral pressure. This can be provided by fixed or automatic vents to outside in which case these should be on two facades, to prevent wind pressures affecting the system – sized to allow air to be relieved at no more than 2.5m/s. A common shaft serving several levels – only the fire floor opens – sized at 2m/s Mechanical ventilation – again only form the fire floor and should not cause excess pressure differentials
- Generally activation should be from an AFD system which identifies which floor the fire is on – class B systems can operate as another class (e.g. A or C) during escape phase and then be manually switched to FF mode. Acc air release should only operate on the fire floor itself.
- A simple analogy to explain the principle
- The science behind the design is relatively simple
- However the more complex the building is the more complicated the calculations become – EN 12101-6 gives a detailed explanation of the process.
- The resistance of the supply duct system is also required to make the system operate at the calculated duty
- To compensate, a number of safety factors are added into the design process, but often there are still issues on site
- The design process makes numerous assumptions regarding leakage rates for walls, doors, windows, etc. The problem comes when the building doesn’t meet up to the rates specified. Often a poor understanding of the system by the architect or builder can lead to inadvertent leakage routes being left, causing the installation to fall short of the design criteria.
- Once the installation is complete, a complex commissioning process is then required
- First check that the system has been installed correctly
- Once the system is up and running the system will need to be balanced and the performance verified
- A manometer is used to measure the pressure differences
- Then measure the pressure on each level with the system running
- A rotating vane anemometer is used to measure the air velocity across the doors and calculate the average.
- Then measure the open door velocities as required by the system design
- The final commissioning procedure is often problematic – it is only at the final stage that it can be established that the pressure cannot be achieved and frantic sealing of building joints takes place. This final testing is best done out of hours as during normal hours, the stairs are generally in constant use by trades people
- There are moves to simplify EN12101-6 but this will not be published until 2011 at the earliest.
- The end. Any questions???