9 System Components

9.1 Powered Smoke Ventilators. The standard of construction and testing of smoke extract fans are governed by the construction products directive if sold and used within the EU, the specific standard being EN12101-3. This standard defines the design requirements, test procedures, performance requirements, classification and quality procedures that a certified product must meet. The classification classes are given below in table 2. Class Temperature °c Minimum functioning period (minutes) F200 200 120 F300 300 60 F400 400 120 F600 600 60 F842 842 30 Not classified As specified by sponsor As specified by sponsor Table 2. Test temperature and functioning time according to classification. The application and use of the smoke extract fan is determined by the system designer Consideration should be given to, but not necessarily limited to, the following: • Fan location • Smoke layer temperature • Method of control • System duty (volume & pressure) • Use for day to day ventilation There are separate requirements for the smoke extract fan if it is to be used for emergency use only or for dual purpose, i.e. day to day ventilation as well as smoke extract. If a ventilator has been tested and certified at full speed operation without the use of controls such as a frequency inverter, then it is only a certified product for that mode of operation. If frequency inverter control is to be used, the designer must ensure that it is suitable for the application. 9.2 Ducts 9.2.1 Ducted Smoke Control Systems Smoke control ducts and any associated ancillaries have to be designed to extract smoke and hot air from the source of a fire. Before the event it is not known where the fire/smoke will occur. There will be a “cause and effect” design which defines which dampers must open or close to provide a path from the fire/smoke source to the classified smoke exhaust ventilator (fan) and thus to outside. This path will vary dependent upon which smoke/fire alarm is triggered. The damper at the fire/smoke location must be open to allow the smoke/heat to be extracted. Any dampers in the extract route must also be fully open (for the least pressure drop/greater volume) to complete that route. Any dampers that isolate spurs or are directly isolating the route (e.g. on the surface of the duct) must be closed. As the damper at the fire/smoke location will be open, the duct now forming the extract path has become part of the fire compartment from which smoke is being extracted. Therefore that duct and any associated dampers, not in the direct path, have to be fire resisting maintaining compartmentation along that path. Conversely all the open dampers have to be proven in their ability to maintain their opening, and their ability to keep the path clear. The ductwork needs to maintain cross-sectional area during an incident, so that increased pressure drop does not occur resulting in a reduced extract rate. To achieve this flexibility, smoke control dampers shall be under the control of a system, that responds to fire or smoke signals. This means that dampers shall be actuated. Spring return actuators shall not be used and fusible links shall not be used, rather tested drive open/drive closed actuators. It is not possible to outguess where a fire will occur. If spring return dampers are used, and during the incident the power fails, the dampers will change state. If closed dampers near to the fan open incorrectly, air would then be drawn from them, rather than from where it is needed. If a damper in the line closed incorrectly extract would simply stop from where it is needed. The designer must take account of potential failure modes during design process and assess the risks associated with potential failures. If balancing is required, this may be achieved by modulating drive open/drive closed actuators responding to a control signal for set point, but with the ability for this to be overridden to drive fully open or fully closed in the event of fire/smoke alarm. If un-motorised balancing dampers are to be used, they shall be modified versions of the tested smoke control dampers to maintain duct integrity and any modifications made must be within the parameters set in the test code. The system designer needs to ensure that any fans are capable of drawing the required extract volumes through these partially closed units and their associated additional pressure drop. Existing British Standards make a requirement for smoke control ducts to have a known performance at 600°C, ancillaries to have proven performance to 300°C; however, no ducting shall compromise compartmentation. It may be seen that to extract smoke from a specific area there is a great likelihood that the duct will cross many compartments and so in most cases will need to be fire resisting. 9.2.2 Single compartment smoke control duct sections Where smoke control ductwork does not need to be fire resisting (i.e. does not maintain compartmentation), smoke control duct sections can be tested to 600°C. The following are the CEN product standard (certification and CE marking), test standard and classification standards respectively. prEN 12101-7: Smoke and heat exhaust ventilation – Part 7: Smoke control duct sections BS EN 1366-9: Fire resistance tests for service installations: Smoke extraction ducts (single compartment) BS EN 13501-4: Fire classification of construction products and building elements - part 4: classification using data from fire resistance tests on components of smoke control systems 26 As an alternative, where such products may not be readily available, any duct tested as fire resisting could meet this requirement, as these tests are made using the standard time time/temperature curve – these test standards are as follows: BS 476-24: Fire tests on building materials and structures – part 24: Method for the determination of the fire resistance of ventilation ducts BS EN 1366-1: Fire resistance tests for service installations: Ducts BS EN 1366-8: Fire resistance tests for service installations: Smoke extraction ducts (multi compartment) Note: Although in the first two instances no specific limits are made with respect to loss of cross-sectional area, BS476-24 includes this as an additional observation, so careful examination of test reports shall be made. If the transition between single compartment smoke control duct and multi-compartment smoke control duct takes place inside the final single compartment at a safe distance from the compartment boundary (protection by fire resisting ductwork), no damper protection would be needed. If the transition takes place at the boundary a multi-compartment smoke control damper shall be installed (not a fire damper). 9.2.3 Multi compartment smoke control duct sections Where smoke control ductwork needs to be fire resisting (i.e. needs to maintain compartmentation), smoke control duct sections can be tested to the standard/time temperature curve, making them fire resisting. The following are the CEN product standard (certification and CE marking), test standard and classification standards respectively. prEN 12101-7: Smoke and heat exhaust ventilation – Part 7: Smoke control duct sections BS EN 1366-8: Fire resistance tests for service installations: Smoke extraction ducts (multi compartment) BS EN 13501-4: Fire classification of construction products and building elements - part 4: classification using data from fire resistance tests on components of smoke control systems As an alternative, where such products may not be readily available, any duct tested as fire resisting could meet this requirement, as these tests are made using the standard time time/temperature curve – these test standards are as follows BS 476-24: Fire tests on building materials and structures – part 24: Method for the determination of the fire resistance of ventilation ducts BS EN 1366-1: Fire resistance tests for service installations: Ducts Note: Although in these instances no specific limits are made with respect to loss of cross-sectional area, BS476-24 includes this as an additional observation, so careful examination of test reports shall be made. 9.3 Dampers 9.3.1 Single compartment smoke control dampers Where smoke control dampers do not need to be fire resisting (i.e. does not maintain compartmentation), smoke control dampers can be tested to 600°C. The following are the CEN product standard (certification and CE marking), test standard and classification standards respectively. 27 prEN 12101-8: Smoke and heat exhaust ventilation – Part 7: Smoke control dampers prEN 1366-10: Fire resistance tests for service installations: Smoke control dampers BS EN 13501-4: Fire classification of construction products and building elements - part 4: classification using data from fire resistance tests on components of smoke control systems Note 1: Automatic control – the above standards state that for the application of smoke control dampers under automatic control of a smoke control system working directly from fire or smoke sensor inputs must be proven by test to shut (and open) within 60 seconds, having been actuated 30 seconds after the start of the test. They shall be tested at the same time as the smoke control damper as part of the assembly. Note 2: Manual intervention - the above standards state that for the application of smoke control dampers under the control of a system that is required to be started by someone, or someone is expecting to have control of smoke control dampers during the incident, must be proven by test to shut (and open) within 60 seconds, having been actuated 25 minutes after the start of the test. They shall be tested at the same time as the smoke control damper as part of the assembly. As an alternative, where such products may not be readily available, any damper tested as fire resisting (tests are made using the standard time time/temperature curve), supported by an ad hoc operation test at elevated temperature (e.g. 300° and/or 600°C for 1 hour etc) using a drive open/drive close actuator could meet this requirement, these test standards are as follows BS EN 1366-2: Fire resistance tests for service installations: Fire dampers - plus ad hoc test report 300° and/or 600°C for 1 hour etc Note: The above does not consider the loss of cross-sectional area of an open damper prEN 1366-10: Fire resistance tests for service installations: Smoke control dampers Note: If a smoke control damper is tested to the requirements of the latter for multi compartment applications (using the fire test curve), it is automatically allowed to apply to single compartment applications 9.3.2 Multi compartment smoke control dampers Where smoke control dampers need to be fire resisting (i.e. need to maintain compartmentation), smoke control dampers can be tested to the standard/time temperature curve, making them fire resisting. The following are the CEN product standard (certification and CE marking), test standard and classification standards respectively. prEN 12101-8: Smoke and heat exhaust ventilation – Part 7: Smoke control dampers prEN 1366-10: Fire resistance tests for service installations: Smoke control dampers BS EN 13501-4: Fire classification of construction products and building elements - part 4: classification using data from fire resistance tests on components of smoke control systems Note 1: Automatic control – the above standards state that for the application of smoke control dampers under automatic control of a smoke control system working directly from fire or smoke sensor inputs must be proven by test to shut (and open) within 60 seconds, having been actuated 30 seconds after the start of 28 the test. They shall be tested at the same time as the smoke control damper as part of the assembly. Note 2: Manual intervention - the above standards state that for the application of smoke control dampers under the control of a system that is required to be started by someone, or someone is expecting to have control of smoke control dampers during the incident, must be proven by test to shut (and open) within 60 seconds, having been actuated 25 minutes after the start of the test. They shall be tested at the same time as the smoke control damper as part of the assembly. As an alternative, where such products may not be readily available, any damper tested as fire resisting (tests are made using the standard time time/temperature curve), supported by an ad hoc operation test at elevated temperature (e.g. 300° and/or 600°C for 1 hour etc) using a drive open/drive close actuator could meet this requirement, – these test standards are as follows BS EN 1366-2: Fire resistance tests for service installations: Fire dampers - plus ad hoc test report 300° and/or 600°C for 1 hour etc Note: The above does not consider the loss of cross-sectional area of an open damper BS EN 1366-2: Fire resistance tests for service installations: Fire dampers - plus modified HOT400/30 test from prEN1366-10 using 300° and/or 600°C for 1 hour etc Note: The latter above is an acceptable test to prEN1366-10, if the 400°C test is undertaken for 30 minutes anyway Any proposed designs shall be presented to building control authorities supported with the necessary tests and reasoning.