Active fire curtain barriers allow designers to build open plan buildings yet still provide compartmentation if the worst happens. Geoff Harris examines a new specification – PAS 121:2007 ‘Specification for active fire curtain barrier assemblies with smoke rating’ – which helps ensure that the right steps are taken.
The more we use fire engineered solutions in complex building design, often extending travel distances, the more imperative it is that we ensure active and passive fire protection systems are fit for purpose. The old saying of ‘belt and braces’ applies now more than ever -with fire protection systems it is not good enough that in the event of a power failure they fail too. The belt has broken and someone forgot to attach the braces – farewell trousers! A funny scenario but not when lives could be at stake.
Many serious fires occur not from single incidents but generally from a combination of errors. During a refurbishment, for example, sprinklers may be turned off, smoke detectors covered to prevent dust activating them and then a fire starts and takes hold when someone is drilling through wood. These are real situations.
How can we prevent fires from spreading and at the same time, protect the means of escape? One product now in wide use in the fire protection arena is the active fire curtain barrier – with full fail-safe by gravity in the event of a total power failure. British Standards Institution document PAS121: 2007 Specification for active fire curtain barrier assemblies and active fire curtain barrier assemblies with smoke rating should be read by designers, specifiers, regulators and enforcers to gain a greater appreciation of this type of product.
Active and passive
These fire curtain barriers are designed to reduce compartment sizes by providing full fire separating elements when initiated by fire alarm systems, local detection or in the event of total power failure. Any firefighter will tell you that the best way to prevent fire spread is by keeping compartment sizes small. In addition fire curtain barriers are used:
– to create protected escape routes as an alternative to fire doors, non-load bearing walls, non-load bearing ceilings or fire shutters
– to create fire separation horizontally, vertically or angled for compartmentation
– as a method of upgrading non-fire resisting elements, for example, in front of non-fire resisting glazing and doorsets, where required for compartmentation or protecting means of escape
– in providing a smoke barrier in conjunction with non-smoke rated doors/shutters and other products protecting openings, to reduce leakage of smoke.
Nightmare scenario?
So let’s take another look at our scenario. The sprinklers, there to minimise fire growth, have been isolated for servicing and the detectors are covered due to hot work taking place. A fire starts and involves the mains electrical supply. In addition, the standby generator fails to start – unfortunately there are many reasons why this could happen even though it shouldn’t. So our fire load spreads and smoke is generated quickly.
Using active fire curtain barriers in these circumstances, however, the spread of fire can be controlled. They descend in a controlled manner to provide a fire separating element, even initially providing progressive smoke containment and so protecting escaping occupants. But this can only be achieved when using full, proven, fail-safe by gravity systems.
Beware that some smoke/fire curtain barrier systems available rely on either a primary or auxiliary power supply to make them descend, so not complying with PAS 121: 2007 or BS EN 12101-1: 2006, the standard for smoke curtains in life safety applications. Products that rely on some means of power can only fulfil a property protection role. Without power they would have stayed up, the fire would have spread and the spread of smoke would endanger lives of escaping occupants, even at distance from the seat of a fire.
There are some intriguing methods to provide insulation to curtain barriers and the PAS 121 development team looked at requirements from Europe as well the UK. The new PAS recognises the role of conventional surface temperature insulation performance when considering the use of active fire curtain barriers as part of either a prescriptive or fire engineered solution. But some countries regard the measuring of radiation as a more important indicator than the surface temperature of the non-fire side of fire separating elements. So the specification also offers an approach based in an ‘insulating zone’ and/or radiation for specific applications, and the effects of radiation on human skin have been included as an annex for information. The reason for this alternative approach is twofold: firstly you cannot fix thermocouples to a reactive surface and secondly, although the curtain barriers are held securely within guides, the curtain barrier material will deflect and/or billow under fire pressure. The distance from the face of the furnace to the thermocouple is then measured and stated as the insulating zone.
So designers are able to re-evaluate designs using these techniques, although they need to recognise that active fire curtain barriers may have an impact on the effective width of an escape route due to barrier deflection or billowing as, unlike rigid walls, they are flexible. Under a prescriptive solution, there will be a need to increase escape route widths to compensate for the reduction in the effective width. Under a fire engineered solution, careful consideration will need to be given the actual width of an escape route where active fire curtain barriers are to be installed.
Other methods of providing insulation were considered, for example using a water curtain to drench the curtain barrier. While this method works, it relies on a constant flow of water. This was deemed unacceptable because firstly, if the water fails the fire separation requirements would be compromised; secondly, the amount of water required could cause severe water damage if flowing continuously to provide just 30 minutes’ protection; and thirdly, such an arrangement may reduce the supply to any sprinklers. There was also a concern over the potential slip hazard along escape routes created by the water.
All fire engineered solutions need to be evaluated in detail by a suitably qualified person and any justification needs to form part of the complete fire safety strategy for the building. Prescriptive testing does not always ensure the products are fit for the intended purpose. The main advantages of using active fire curtain barriers as part of a fire engineered solution are:
– maintaining an open plan design while reducing the total compartment size, or to protect escape routes in the event of a fire, thereby enhancing life safety and property protection
– supplement phased evacuation strategies by closing off areas and re-compartmenting, thereby restricting fire spread. In this case only the evacuation of people within the compartment of fire origin may initially be necessary.
Staged activation
Active fire curtain barriers can also be multifunctional. They act initially as smoke barriers within a smoke and heat exhaust ventilation system (SHEVS) remaining 2.5m above floor level for a predetermined time, before deploying fully to provide a fire separating element. They can be installed such that only local curtain barriers are required to descend at a given temperature rise, without the need to deploy all of them. So escaping occupants in other areas are provided with a clear field of vision and means of escape, while providing easier and safer access for firefighters.
Methods of retracting curtain barriers for egress can also be incorporated, remembering that barriers across escape routes should only descend if initiated by a heat detector or fusible link. There are two main types; one where the curtain barrier rises and holds open for a predetermined time before closing, and one for fire service access that raises the curtain barrier only when a button is pressed, allowing a brief look under so reducing the likelihood of a flashover. Where curtain barriers are overlapped it is quite feasible for the fire service to use the overlap for access purposes, which will greatly reduce the opening required for firefighting jets.
In conclusion, active fire curtain barriers are deployed when and where needed and remain hidden within the ceiling until there is detection of smoke, fire or fire alarm activation. When used as part of a fire engineered design, fire curtain barrier assemblies become a critical element of that design but if they do not deploy to their operational position, the system will not perform as designed. However even in the event that other elements of the fire protection system do not function, for example due to total power failure, the true gravity fail-safe fire curtain barriers in the fire operational position will provide essential fire separation.
Geoff Harris is chairman of the European committee for smoke control, CEN TC 191/SC1.
WHAT’S IN THE SPECIFICATION?
Publicly Available Specification (PAS) 121: 2007 for active fire curtain barrier assemblies, and active fire curtain barrier assemblies with smoke ratings provides comprehensive details, including test requirements, for companies or individuals designing, manufacturing, installing and employing active fire barrier assemblies.
The PAS was produced as a pre-curser to a full British Standard to fill a gap that exists in the field of active fire containment. The active fire barrier assembly requirements are intended to provide the fire engineer or designer with an alternative to fire doors, shutters, walls and ceilings which fulfil the fire separation design requirements for life safety and property protection. In addition it provides regulators with a method of ensuring fitness for purpose.
The PAS explains in detail what type of initiation device should be used depending upon location and provides detailed test methods. In addition it highlights alternative test methods for a flexible product based on requirements not contained within other British Standards, for example ‘radiation’ which is deemed the most important by fire engineers when calculating tenability to life safety and in Holland as the way to prevent fire spread as opposed to just the surface temperature.
Active fire curtain barriers allow designers to build open plan buildings yet still provide compartmentation if the worst happens. Geoff Harris examines a new specification – PAS 121:2007 ‘Specification for active fire curtain barrier assemblies with smoke rating’ – which helps ensure that the right steps are taken.
The more we use fire engineered solutions in complex building design, often extending travel distances, the more imperative it is that we ensure active and passive fire protection systems are fit for purpose. The old saying of ‘belt and braces’ applies now more than ever –with fire protection systems it is not good enough that in the event of a power failure they fail too. The belt has broken and someone forgot to attach the braces – farewell trousers! A funny scenario but not when lives could be at stake.
Many serious fires occur not from single incidents but generally from a combination of errors. During a refurbishment, for example, sprinklers may be turned off, smoke detectors covered to prevent dust activating them and then a fire starts and takes hold when someone is drilling through wood. These are real situations.
How can we prevent fires from spreading and at the same time, protect the means of escape? One product now in wide use in the fire protection arena is the active fire curtain barrier – with full fail-safe by gravity in the event of a total power failure. British Standards Institution document PAS121: 2007 Specification for active fire curtain barrier assemblies and active fire curtain barrier assemblies with smoke rating should be read by designers, specifiers, regulators and enforcers to gain a greater appreciation of this type of product.
Active and passive
These fire curtain barriers are designed to reduce compartment sizes by providing full fire separating elements when initiated by fire alarm systems, local detection or in the event of total power failure. Any firefighter will tell you that the best way to prevent fire spread is by keeping compartment sizes small. In addition fire curtain barriers are used:
• to create protected escape routes as an alternative to fire doors, non-load bearing walls, non-load bearing ceilings or fire shutters
• to create fire separation horizontally, vertically or angled for compartmentation
• as a method of upgrading non-fire resisting elements, for example, in front of non-fire resisting glazing and doorsets, where required for compartmentation or protecting means of escape
• in providing a smoke barrier in conjunction with non-smoke rated doors/shutters and other products protecting openings, to reduce leakage of smoke.
Nightmare scenario?
So let’s take another look at our scenario. The sprinklers, there to minimise fire growth, have been isolated for servicing and the detectors are covered due to hot work taking place. A fire starts and involves the mains electrical supply. In addition, the standby generator fails to start – unfortunately there are many reasons why this could happen even though it shouldn’t. So our fire load spreads and smoke is generated quickly.
Using active fire curtain barriers in these circumstances, however, the spread of fire can be controlled. They descend in a controlled manner to provide a fire separating element, even initially providing progressive smoke containment and so protecting escaping occupants. But this can only be achieved when using full, proven, fail-safe by gravity systems.
Beware that some smoke/fire curtain barrier systems available rely on either a primary or auxiliary power supply to make them descend, so not complying with PAS 121: 2007 or BS EN 12101-1: 2006, the standard for smoke curtains in life safety applications. Products that rely on some means of power can only fulfil a property protection role. Without power they would have stayed up, the fire would have spread and the spread of smoke would endanger lives of escaping occupants, even at distance from the seat of a fire.
There are some intriguing methods to provide insulation to curtain barriers and the PAS 121 development team looked at requirements from Europe as well the UK. The new PAS recognises the role of conventional surface temperature insulation performance when considering the use of active fire curtain barriers as part of either a prescriptive or fire engineered solution. But some countries regard the measuring of radiation as a more important indicator than the surface temperature of the non-fire side of fire separating elements. So the specification also offers an approach based in an ‘insulating zone’ and/or radiation for specific applications, and the effects of radiation on human skin have been included as an annex for information. The reason for this alternative approach is twofold: firstly you cannot fix thermocouples to a reactive surface and secondly, although the curtain barriers are held securely within guides, the curtain barrier material will deflect and/or billow under fire pressure. The distance from the face of the furnace to the thermocouple is then measured and stated as the insulating zone.
So designers are able to re-evaluate designs using these techniques, although they need to recognise that active fire curtain barriers may have an impact on the effective width of an escape route due to barrier deflection or billowing as, unlike rigid walls, they are flexible. Under a prescriptive solution, there will be a need to increase escape route widths to compensate for the reduction in the effective width. Under a fire engineered solution, careful consideration will need to be given the actual width of an escape route where active fire curtain barriers are to be installed.
Other methods of providing insulation were considered, for example using a water curtain to drench the curtain barrier. While this method works, it relies on a constant flow of water. This was deemed unacceptable because firstly, if the water fails the fire separation requirements would be compromised; secondly, the amount of water required could cause severe water damage if flowing continuously to provide just 30 minutes’ protection; and thirdly, such an arrangement may reduce the supply to any sprinklers. There was also a concern over the potential slip hazard along escape routes created by the water.
All fire engineered solutions need to be evaluated in detail by a suitably qualified person and any justification needs to form part of the complete fire safety strategy for the building. Prescriptive testing does not always ensure the products are fit for the intended purpose. The main advantages of using active fire curtain barriers as part of a fire engineered solution are:
• maintaining an open plan design while reducing the total compartment size, or to protect escape routes in the event of a fire, thereby enhancing life safety and property protection
• supplement phased evacuation strategies by closing off areas and re-compartmenting, thereby restricting fire spread. In this case only the evacuation of people within the compartment of fire origin may initially be necessary.
Staged activation
Active fire curtain barriers can also be multifunctional. They act initially as smoke barriers within a smoke and heat exhaust ventilation system (SHEVS) remaining 2.5m above floor level for a predetermined time, before deploying fully to provide a fire separating element. They can be installed such that only local curtain barriers are required to descend at a given temperature rise, without the need to deploy all of them. So escaping occupants in other areas are provided with a clear field of vision and means of escape, while providing easier and safer access for firefighters.
Methods of retracting curtain barriers for egress can also be incorporated, remembering that barriers across escape routes should only descend if initiated by a heat detector or fusible link. There are two main types; one where the curtain barrier rises and holds open for a predetermined time before closing, and one for fire service access that raises the curtain barrier only when a button is pressed, allowing a brief look under so reducing the likelihood of a flashover. Where curtain barriers are overlapped it is quite feasible for the fire service to use the overlap for access purposes, which will greatly reduce the opening required for firefighting jets.
In conclusion, active fire curtain barriers are deployed when and where needed and remain hidden within the ceiling until there is detection of smoke, fire or fire alarm activation. When used as part of a fire engineered design, fire curtain barrier assemblies become a critical element of that design but if they do not deploy to their operational position, the system will not perform as designed. However even in the event that other elements of the fire protection system do not function, for example due to total power failure, the true gravity fail-safe fire curtain barriers in the fire operational position will provide essential fire separation.
Geoff Harris is chairman of the European committee for smoke control, CEN TC 191/SC1.
WHAT’S IN THE SPECIFICATION?
Publicly Available Specification (PAS) 121: 2007 for active fire curtain barrier assemblies, and active fire curtain barrier assemblies with smoke ratings provides comprehensive details, including test requirements, for companies or individuals designing, manufacturing, installing and employing active fire barrier assemblies.
The PAS was produced as a pre-curser to a full British Standard to fill a gap that exists in the field of active fire containment. The active fire barrier assembly requirements are intended to provide the fire engineer or designer with an alternative to fire doors, shutters, walls and ceilings which fulfil the fire separation design requirements for life safety and property protection. In addition it provides regulators with a method of ensuring fitness for purpose.
The PAS explains in detail what type of initiation device should be used depending upon location and provides detailed test methods. In addition it highlights alternative test methods for a flexible product based on requirements not contained within other British Standards, for example ‘radiation’ which is deemed the most important by fire engineers when calculating tenability to life safety and in Holland as the way to prevent fire spread as opposed to just the surface temperature.
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