Code of Practice for Design, Installation, Commissioning & Maintenance of Duct Smoke Detector (DSD) Systems

Transcription

1 Code of Practice for Design, Installation, Commissioning & Maintenance of Duct Smoke Detector (DSD) Systems Issue 1.0 Page 1 of 35

2 Fire Industry Association Code of Practice for Design, Installation, Commissioning & Maintenance of Duct Smoke Detector (DSD) Systems This Code of Practice is intended as a general guidance and is not a substitute for detailed advice in specific circumstances. Although great care has been taken in the compilation and preparation of this publication to ensure accuracy, the FIA cannot in any circumstances accept responsibility for errors, omissions or advice given or for any losses arising from reliance upon information contained in this publication. Fire Industry Association Tudor House Kingsway Business Park Oldfield Road Hampton TW12 2HD Telephone: Fax: Copyright: The contents of this Code of Practice are copyright of the Fire Industry Association Limited. Reproduction or publication in whole or part without prior permission is expressly forbidden. Issue 1.0 Page 2 of 35

3 Contents Introduction Scope Normative References Terms, definitions and abbreviations The need for DSDs Definition of DSD systems Exchange of information and definition of responsibilities Variations of recommendations Design considerations Product Standards & Marking Limitation of False Alarms Installation Commissioning and Handover Maintenance User Responsibilities...23 Annex A (informative) Enhanced and High Sensitivity Duct Smoke Detectors...26 Annex B (informative) Example forms...28 FIGURES Figure 1: DSD system - communication options... 8 Figure 2: Typical positions for DSD in air-handling systems... 9 Figure 3: Examples of potential DSD connections in a HVAC Figure 4: DSD Placement: DSD Placement Issue 1.0 Page 3 of 35

4 Introduction The primary purpose of duct smoke detection is to prevent injury, panic, and property damage by reducing the spread (re-circulation) of smoke. Duct smoke detectors can also serve to protect the air conditioning system itself from fire and smoke damage, and can be used to assist in equipment protection application, for example, in the ventilation/exhaust duct work of EDP areas. The use of duct smoke detectors is not a substitute for an area smoke detector or early warning detection. They are not generally considered as primary alarm devices for a fire detection and fire alarm system because of inevitable dilution of the smoke and non-guaranteed airflow in the duct. In specific instances, it may be possible to use high sensitivity smoke detection within ventilation ducts as the primary detection system. However, this would need to be supported by appropriately qualified engineering solutions agreed by all interested parties and documented in accordance with the relevant Standards. Duct smoke detectors may be either a stand-alone actuator for a fire protection system or integrated into a fire detection and fire alarm system. In the latter case, the control equipment of the fire detection and fire alarm system may provide the facility to operate the air control system. A number of forms are provided in the Appendices to be used as checklists to ensure that the correct information is transferred through each stage of the process (Planning-Design- Installations- Commissioning- Maintenance). It has been assumed in the drafting of this FIA Code of Practice that the execution of its provisions will be entrusted to appropriately qualified and competent people. 1 Scope This FIA Code of Practice provides recommendations for the planning, design, installation, commissioning and maintenance of duct smoke detection (DSD) systems. It identifies categories of Issue 1.0 Page 4 of 35

5 DSD systems and typical applications where such systems are used. It also provides specific design rules on common applications and guidance on good practice. This Code of Practice does not include recommendations for the use of DSD used as primary detection systems for general early warning fire detection in buildings. This Code of Practice does not include recommendations for the overall smoke control strategy and the associated actuating smoke control devices. 2 Normative References BS :2002 BS 6266:2002 BS 7974:2001 BS 9999:2008 pren 54-27:2001 EN 54-20:2004 EN 54-2 :1997 EN 54-4 :2001 HTM Part B Other publication Fire detection and fire alarm systems for buildings Part 1: Code of Practice for system design, installation, commissioning and maintenance Code of Practice for fire protection for electronic equipment installations Application of fire safety engineering principles to the design of buildings Code of Practice Code of Practice for fire safety in the design, management and use of buildings Fire detection and fire alarm systems Part 27: Duct smoke detectors Fire detection and fire alarm systems Part 20: Aspirating smoke detectors Fire detection and fire alarm systems Part 2.Control and indicating equipment Fire detection and fire alarm systems Part 4. power supply equipment Fire detection and alarm systems. Department of Health Fire Industry Association (FIA) Code of Practice for design, installation, commissioning and maintenance of aspirating smoke detectors (ASD systems) 3 Terms, definitions and abbreviations For the purpose of this document the terms and definitions in BS : 2002 and the following apply: 3.1 aspirating smoke detector ASD A smoke detection system, in which air and aerosols are drawn through a sampling device and carried to one or more smoke sensing elements by an integral aspirator (e.g. fan or pump) 3.2 control and indicating equipment CIE Equipment in accordance with EN condition warning (pre-alarm warning) Status of a DSD reflecting a change of signal at the control equipment which is greater than the ambient non-fire state but below the normal fire state 3.4 dilution effect Reduction in the concentration of smoke caused by the introduction of clean air from other part(s) of the building or from outside air intakes Issue 1.0 Page 5 of 35

6 3.5 duct smoke detector DSD Apparatus that monitors the air in a duct to detect the presence of smoke 3.6 fire protection system FPS A group of devices that, in combination, are capable of automatically actuating measures to limit the effect of fire EXAMPLE Fire dampers, smoke control systems and fire fighting systems. 3.7 heating, ventilation and air-conditioning HVAC Comfort systems installed in buildings which uses duct-work. 3.8 power supply equipment PSE Equipment in accordance with EN sampling device A component or series of components or dedicated device (e.g. a single sampling pipe, network of sampling pipes, dedicated duct probe or hood) which transfers samples of air to the smoke detector 3.10 smoke control system System used to control the spread and/or aid the extraction of smoke in and around buildings EXEMPLE Smoke control systems may incorporate such sub-systems as: Extraction, Pressurization or dilution, Containment (smoke control doors, lobbies, dampers or shutters in ventilation systems). NOTE Smoke control system may incorporate elements of the HVAC system stratification formation of smoke into layers within the duct NOTE Stratification can be caused by thermal buoyancy of smoke and is more likely to occur when air velocity is low. 4 The need for DSDs COMMENTARY ON 4 DSDs provide smoke detection in ventilation ducts with the purpose to control the spread of smoke in the building. DSDs can operate as stand-alone systems or can be integrated as part of the fire detection and fire alarm system. In the latter case, the DSD system designer must still maintain compliance to National Standards, especially for fault monitoring, zoning and battery standby, etc. Issue 1.0 Page 6 of 35

7 Preventing the spread of smoke through a building in the event of a fire is a primary objective of fire safety engineering. One of the main routes for the distribution of smoke is via air handling and ventilation ducting. It is therefore necessary to control the air handling and ventilation system in the case of fire or smoke in the duct. While this control may be initiated from the detection of smoke within the fire compartment, where such detection is not provided (or is limited), reliable detection of smoke within the duct will be necessary. The following recommendations apply when establishing the need for DSDs: 4.1 Where there is uncertainty regarding the need for a duct smoke detection system, or the type of system that should be used (see clause 5) reference should be made, by the potential purchaser or user to one or more of the following: a) National and local codes of practice for fire safety in buildings, e.g. BS 9999 b) Specification for smoke control systems, e.g. EN 12101, relevant parts c) Local building codes and regulations, e.g. The Building Regulations, Approved Document B d) Health Technical Memorandum Part B, Fire detection and alarm systems. Department of Health e) Guidance documents that support fire safety codes f) Any authority responsible for enforcing fire safety codes applicable to the premises. 4.2 The purchaser or user should ensure that the designer of a duct smoke detection system is adequately apprised of the detection and smoke control objectives of the system and any other relevant requirements of the enforcing authorities and insurers. 5 Definition of DSD systems COMMENTARY ON 5 This section outlines a means of defining DSD systems encompassing all the elements essential to the design in such a way that any individual system can be described in a single unambiguous phrase. This definition of DSD systems takes into account the following: Purpose of the DSD system Extent of coverage Position of the DSD in the HVAC system Type of detectors (as defined in EN a) Purpose of the DSD system Before designing a DSD system it is important to determine its purpose within the application. DSD systems may communicate with different elements of the fire control system and/or building control system as illustrated in Figure 1. Issue 1.0 Page 7 of 35

8 Figure 1: DSD system - communication options Most DSD systems are installed to achieve one or more of the following objectives: 1) prevent smoke from spreading from one area of a building to another or from being re-circulated by the air-handling system, e.g. by closing appropriate dampers and/or switching off air-handling system fans 2) detect fire in the air-handling system, e.g. motors and electrical wiring NOTE: DSDs are not suitable for the detection of fire within ductwork which handles smoke as part of its normal operation, e.g. kitchen/cooking extraction systems 3) prevent smoke accumulating in an area of a building, e.g. by opening smoke vents and/or activating smoke control fans 4) prevent smoke entering the air-handling system of a building from outside. b) Extent of coverage Having identified the purpose(s) of the DSD system, it is important to clearly state the intended coverage. The following system coverage needs to be identified: 1) Full coverage DSDs installed throughout the air-handling system of a building, may be broken down into fire compartments or by floor 2) Partial coverage DSDs installed to protect specific areas of a building from smoke damage, e.g. computer suites, archive rooms c) Position of DSDs in the air-handling system The positioning of DSDs can only be considered once the design of the air-handling system has been completed, and the purpose and extent of the DSD system have been established. Issue 1.0 Page 8 of 35

9 Dependent on the size and configuration of the HVAC system, DSDs are installed at: the supply side of the HVAC system the point of entry of a common return the return system of each floor the point of fresh air intake d) Type of detectors Figure 2: Typical positions for DSD in air-handling systems For the purpose of this Code of Practice, DSD systems have been classified into the following types: Point type internal systems using point type detector mounted directly inside the duct (according to EN54-27 Type 1 and Type 2 DSD and also Type 6 DSDs based on point detectors not approved to EN54-7) Point type external systems using point type detector within an enclosure mounted outside the duct with additional mechanical means of sampling the air (Type 3 and Type 4 DSD according to EN 54-27) NOTE: Point type smoke detectors used in DSDs include ionization, optical or multi-sensor detectors. Aspirated systems using ASD sampling from the duct (Type 5 according to EN 54-27) Others systems using detection arrangements not covered by the above; e.g. optical line-type smoke detectors. The following recommendations apply when defining the type of DSD system used: 5.1 The purchaser of the system or his agent should provide the designer with the definition of the DSD system required (e.g. in purchase or tender specifications). Issue 1.0 Page 9 of 35

10 5.2 The definition of the DSD system should state the purpose and extent of the system, the anticipated positioning and type(s) of the DSDs to be used. 5.3 Any statutory requirements imposed by enforcing authorities and any requirements imposed by property insurers for a fire alarm system should be identified in the definition of the DSD system. 5.4 If the designer is not provided with the definition of the DSD system, the designer should make clear to the purchaser or his agent the assumed definition of the DSD system used for the design that is proposed, prior to an order for the system being placed. 5.5 The definition of the DSD system should be stated or referenced in the design certificate. 6 Exchange of information and definition of responsibilities COMMENTARY ON 6 The purpose of the DSD system is to control the spread of smoke in the building either as a stand- alone system or as a system connected to the building fire detection and fire alarm system. It is, in particular, important that the system design suitably supports the required actions that are necessary in order to prevent the spread of smoke. It is important that the system requirements, including those imposed by the need to restrict the spread of smoke, the configuration of the ventilation duct system, and its specific use within the building, is ascertained as accurately as possible by consultation between the user or purchaser and other interested parties, such as the enforcing authority or fire insurer. 6.1 Exchange of information The following recommendations apply to the exchange of information: The user or purchaser of the DSD system, or an appointed representative, should ensure that there is consultation at or prior to the system design stage with all relevant interested parties. The responsibility for each of the following stages should be clearly defined: System Planning System Design Installation Commissioning Maintenance The information relevant to each of the stages should be clearly recorded. Example forms reflecting the guidance in this Code of Practice are in Annex B The system planning stage should provide a clear indication of the DSD system category and include details of the environmental conditions to be anticipated, proposed processes and the system performance test proving requirements. On the basis of these consultations, documents should be prepared; these may include but are not limited to: a) details of the installation proposed, including DSD system category b) any special accommodation required for the equipment c) any special structural provision required for the equipment or its associated pipework such as supports d) any link to the main fire detection and fire alarm system, smoke control system and/or building management systems e) actions in the event of an alarm f) any environmental conditions and processes which may affect detection or have the potential for false alarms g) any functional/performance tests for the system Issue 1.0 Page 10 of 35

11 h) any future maintenance access requirements 6.2 Definitions of responsibilities COMMENTARY ON 6.2 It is highly desirable that, at the contract stage, one organization should be designated to take overall responsibility for the performance of the DSD system, and that responsibility is clearly defined in the documentation. The following recommendations apply to the definition of responsibilities: Where a DSD system is to be interfaced with another system that is the responsibility of another organization, the responsibility of each organization should be clearly defined and documented Consideration should be given at the contract stage to ensure that the continued support, corrections or modifications throughout the expected life of the system are subject to the initial design criteria Care should be taken by the user or purchaser to monitor for any changes at the location that could adversely affect the DSD system operation as identified by the manufacturer / specialist. 6.3 Action in the event of an alarm COMMENTARY ON 6.3 Where a DSD is used as a stand-alone device within the HVAC it will provide a signal that smoke has been detected. The action in the event of an alarm, e.g. closing of smoke dampers, switching off fans is predetermined. Where a DSD is integrated as part of the FDAS, the action in the event of an alarm may be: - determined as in the case of a stand-alone device, or - controlled as part of the FDAS response, or - a combined element of both Figure 3 illustrates examples of the connections that realise the desired actions in the event of alarm as follows. 1. Turn off supply fan(s) 2. Turn off conditioning equipment 3. Close dampers (using local control) 4. Signal to the Fire panel (or building control system) to raise alarm and/or trigger appropriate actions 5. Close dampers (using remote control via the fire panel or building control system) Note: more complex arrangements/actions may be provided e.g. to provide for smoke extraction Issue 1.0 Page 11 of 35

12 Figure 3: Examples of potential DSD connections in a HVAC The following recommendations apply when determining actions in the event of an alarm: The actions required in the event of an alarm from a DSD should be pre-planned and the subject of early discussions between the interested parties. 6.4 Consultations COMMENTARY ON 6.4 It is advisable that there also be relevant consultation between the user or purchaser and the designer of the DSD system. The extent to which such a consultation is necessary may be minimal for simple systems needing only few DSD and/or smoke prevention control actions. In more complex HVAC systems, there will be a need for extensive consultation between the user or purchaser, the enforcing authority the system designer and, possibly, specialist consultants. If the building is under the control of more than one occupant then any new processes or changes to the HVAC system may adversely affect the operation of any DSD system installed elsewhere in the building. In such cases, it is particularly important that consultation between the relevant interested parties continues throughout the life of the system user or purchaser of the DSD system (or an appointed representative of these parties such as a consultant) should ensure that, to the extent appropriate, there is consultation at or prior to the system design stage with all relevant interested parties; these include the authority responsible for enforcing fire safety legislation; and the property insurer The designer of the DSD should ensure that, to the extent appropriate, there is consultation at the system design stage with all relevant interested parties including the following: a) the user or purchaser of the DSD system Issue 1.0 Page 12 of 35

13 b) supplier(s) of any third party equipment to which the DSD report c) the heating and ventilation designer d) the building services manager e) consultants, especially specialists in the design of HVAC systems If the building is under the control of more than one occupant, the user or purchaser of the DSD system (or an appointed representative of these parties such as a consultant) should ensure that consultation takes place with all the relevant interested parties early in the planning stage of any DSD system and during the whole life of the system. 7 Variations of recommendations This document is a Code of Practice and, as such, its contents take the form of recommendations, rather than requirements. The recommendations are primarily based on recognised good practice in the design, installation, commissioning and maintenance of DSD systems. In certain circumstances, variations from the recommendations may be necessary even though in general, the user, purchaser, enforcing authority or insurer requires strict compliance with this Code of Practice. These variations refer to aspects of the design that were appropriate and intentional, albeit not compliant with one or more recommendations of this Code of Practice. It does not, however, imply that the designer or installer has freedom to ignore the recommendations of this Code of Practice under circumstances in which a user, purchaser, enforcing authority or insurer seeks compliance with it. Variations always need to be the subject of specific agreement amongst all interested parties and need to be clearly identified in all relevant system documentation. 8 Design considerations 8.1 General When designing DSD systems, the following aspects require consideration: a) the performance of the DSD itself, including the sampling tubes where appropriate b) the function of the DSD system whether it be stand alone or an integral part of the overall FDAS c) the ability of the DSD system to be properly maintained Issue 1.0 Page 13 of 35

14 8.2 Performance of DSDs COMMENTARY ON 8.2 The ability of the DSD to detect smoke is dependent on the correct application of the appropriate technology. To ensure that DSDs operate correctly it is important that the following are taken into consideration: what affects the smoke getting into the sampling element, its positioning in the duct in relation to its width, the proximity of grills and bends in the duct work, possible airflow-induced stratification, which may occur in very long, uninterrupted straight runs of duct work or very wide ducts, for point type external DSDs using sampling tube(s), their correct positioning and orientation in the duct, environmental conditions, for example, humidity, thermal stratification, long term effect of pollution such as dust, dilution effects which might be caused by multiple air intakes or a wide range of flow rate in the duct, the increased fire load and/or the attenuation of smoke caused by filters, the effects of sampling tube length, air leaks on the operational pressure differential, depending on the purpose of the system, the location of DSD in the duct, for example, in the air supply side or the air extract side. The following recommendations apply regarding the performance of DSDs: The specification of the DSD should match the range of air velocity that may be present in the duct DSDs should be positioned at least three duct widths downstream of any return grills or bends in the duct work and in the upper half of the duct if mounted horizontally (see figure 4). Figure 4: DSD Placement: DSD Placement Point type internal DSD should be mounted centrally at the top of the duct Point type external and aspirating type DSDs employing sampling tubes should cover the wider dimension of the duct and the length of the sampling tube should be, at least, two thirds of that dimension. NOTE 1 If the height and width of the duct are of similar dimension, mounting the DSD vertically is preferable in order to overcome potential stratification of hot smoke, ensuring that sampling will occur at least within the top third of the duct Reference should be made to the manufacturer s specifications and recommendations for other types of DSDs. Issue 1.0 Page 14 of 35

15 8.2.6 The environmental performance of the DSD should be suitable for the application environment, particularly with respect to temperature, humidity and vibration. NOTE 2: The air temperature inside heating ducts can exceed the maximum operating temperature of standard EN 54-7 detectors which may be used in some internal point type DSDs The positioning of DSDs in the HVAC system should be in accordance with the purpose and extent of the air-handling system (see 5). In particular, this should take into consideration any subdivision of the building into fire compartments and the positioning of fire/smoke dampers. NOTE 3: Locating DSDs upstream of air intakes, exhaust air outputs and fans in high-flow systems may minimize the effects of smoke dilution which can occur in duct ventilation systems DSDs intended to control smoke movement should be located upstream of any filters. Where there is a specific requirement to monitor filters for fire, additional DSDs should be used for this purpose. 8.3 DSD system integration COMMENTARY ON 8.3 The purpose of installing smoke detection in ducts is to ensure that appropriate actions are automatically put in place in the event of a fire (see 6.3). Hence, it is important that DSDs are correctly integrated in an overall control system, either as stand-alone unit(s) or as part of the fire detection and fire alarm system in the building. DSDs may be configured as stand-alone systems or integrated within a FD&A system. Stand-alone DSDs may be connected to the CIE of FD&A systems for supervisory purposes. Typically the DSD will be integrated within the FD&A system and the DSD will signal when it has been activated. It cannot be relied upon as primary detection of fires in buildings because the fire detection efficacy will be affected by the fan operation and dilution effects. Therefore, the DSD only provides supplementary detection to the FD&A system. Fire signals from the DSD will be used by the FD&A system to initiate appropriate fire protection measures. In stand-alone applications (direct signalling with the smoke control system/hvac), a duct smoke detector is often used to shut down a specific HVAC unit or fan to control the spread of smoke locally. Duct smoke detectors may also be used to activate specific HVAC units or fan systems to facilitate the extraction of smoke from a specific fire/smoke compartment. The following recommendations apply regarding DSD system integration: DSDs should provide signals to enable the initiation of the smoke control actions specified in the system design DSDs should provide visual indications in accordance with EN These should be local to the DSD such that they can easily be seen When integrated within a FD&A system, DSDs should signal fault conditions to the CIE. NOTE 1 Examples of fault conditions are power failure, detector removal and wiring faults When integrated within a FD&A system, the power supply to the DSD should comply with EN If the power to the DSD is not supplied by the CIE then the DSD should signal a fault to the CIE if the power fails When used as an actuator to a FPS, i.e. in a stand-alone application, a DSD should signal a fault to the FPS if its power fails. NOTE: When used as an actuator to a FPS, a power supply complying with EN 54-4 is not necessary although it is recommended Stand-alone DSDs should provide visual indications of fire, fault and power-on in accordance with EN When the DSD also provides an audible alarm, this should be at least 5 db(a) above the normally expected background level If the DSD is used as an actuator for a FPS, i.e. stand-alone system then the DSD shall be provided with means for manual resetting of the alarm or fault condition. Issue 1.0 Page 15 of 35

16 NOTE 3: The means for resetting may be integral to or remote from the DSD. 8.4 Design for maintenance COMMENTARY ON 8.4 The continued reliable operation of a DSD system depends on the ability to carry out effective maintenance over the installed life of the system. DSDs are often installed in positions which are difficult to access hence it is important to consider the following maintenance needs in DSD system design: a) accessibility for visual inspection and servicing of component parts b) provision of facilities to carry out specified commissioning and maintenance tasks c) fault monitoring in stand-alone configurations, including local fault indication The following recommendations apply regarding the design of DSD systems for maintenance: The selection of the DSD should be such as to maximize ease of maintenance and testing Each DSD should be mounted in a position which allows good physical and visual access for inspection and maintenance The DSD system design should include provisions for carrying out specified tests for verifying performance. For example: a) In the case of point type internal DSDs, access should be provided on the duct for inspection and/or servicing and testing b) In the case of ASD type DSDs a test sampling point, which is closed during normal operation, may be provided externally to the duct for the convenience of maintenance testing The provision of access for maintenance of the DSD should be such that the integrity of the duct is not compromised The fault monitoring indication of stand-alone DSDs and associated equipment should be readily available to alert Responsible Person nel to the need for maintenance. 8.5 Design documentation Sufficient design documentation should be provided to ensure the correct installation, commissioning and maintenance of the DSD system. 9 Product Standards & Marking COMMENTARY ON 9 The reliability of the DSD system to perform its functions on demand is, to a significant degree, governed by the reliability of individual components. In general, it is advisable that all components in the DSD system conform to relevant British Standards and have approval under a recognized certification scheme. Compatibility of DSD system components, including interconnecting cables, is essential to ensure reliable operation of the overall system. In addition to the marking required by the applicable Standard, (e.g. model number, manufacturer's name) and marking required by European Directives and Regulations (e.g. CE mark and notified body reference), it is important that DSDs are adequately marked to identify their application type. The following recommendations apply to product Standards and marking: 9.1 The duct smoke detector should be approved to BS EN NOTE 1: BS EN requires that point type internal DSD and point type external DSD comply with EN 54-7 and aspirated DSD comply with EN NOTE 2 EN is currently available as a FprEN and is at the final formal voting stage. 9.2 Power supply equipment used with stand-alone DSD should be approved to BS EN The designer of DSD systems should ensure that components used in the systems are able to function correctly when interconnected using the specified cable(s) or wireless link(s). Issue 1.0 Page 16 of 35

17 9.4 In addition to the marking mandated by applicable Standards, DSD components should carry suitable marking to identify their use within the overall system. 10 Limitation of False Alarms COMMENTARY ON 10 False alarms may be categorized into unwanted alarms caused by fir-like phenomena in the protected environment and equipment false alarms caused by faults in the detection equipment or system. BS : 2002 section 3 defines two further categories; malicious false alarms arising from malicious actions and false alarms with good intent arising from intentional but misguided operation of a call point. In relation to DSD systems only unwanted alarms and equipment false alarms are considered. DSD systems operate at marginally enhanced levels of sensitivity. Specifically pren requires that they signal an alarm before the smoke concentration in the fire test room reaches 0.6 db/m - compared to an end-oftest condition of 2 db/m for point type smoke detectors approved to EN However, in the majority of DSD systems unwanted alarms due to enhanced sensitivity are uncommon. Common causes of unwanted alarms when they do occur are: lack of testing and maintenance of detectors which have become dirty and, as a consequence, oversensitive incorrect choice of detector, technology or environmental specification for the conditions in the installed space change of use in the occupied space or changes in the specification of the HVAC installation in areas that may include smoke generation events such as concerts, ceremonies and discos disturbance of a duct that has a significant build up of dirt or dust including sudden changes in the flow which disturb dust built up in the duct condensation occurring within the detector as a result of humidity in the duct Many DSD systems incorporate features to minimise the likelihood of false alarms and/or features specifically intended to overcome or manage the common causes of false alarms. These are specific to particular types of DSD and individual products but may include one or more of the following: Variable Alarm Thresholds/settings Drift compensation Alarm decision algorithms Dust rejection algorithms Physical filtering of the sampled air Many ASD systems used as type 5 DSDs incorporate further features to minimise false alarms such as event logs, multiple alarm thresholds and referencing. See the FIA ASD Code of Practice for further details. Issue 1.0 Page 17 of 35

18 The following recommendations apply to limitation of false alarms: 10.1 Correct installation and maintenance of the DSD in accordance with the manufacturer's instructions and the recommendations in clauses 11 and 13 are essential to minimise the risk of false alarms Whenever a false alarm is triggered the cause should be carefully investigated and action should be taken and recorded to ensure it is not likely to cause further false alarms. 11 Installation 11.1 General COMMENTARY ON 11.1 Dependant on the type, DSDs may be fitted within the duct, protruding into the duct or mounted in an enclosure with sampling tubes protruding into the duct. Many aspects of the installation of DSDs are product specific and, therefore, it is important that, whatever the type of DSD used, the installation instructions provided by the supplier are followed. In particular, these instructions may specify hole diameters or entry dimensions and positions, where to locate mounting holes for detector enclosure, sampling tubes, access panels, or doors. National Standards and Regulations, such as BS and BS 7671, apply to the electrical installation of DSD systems. The following general recommendations apply to the installation of DSDs: Installation of the DSD should be carried out in accordance with the manufacturer s installation instructions The DSD should be installed according to the site design specification (see 8.5) Electrical installation must be carried out in accordance with the applicable national Standards and Regulations, in particular BS and BS On completion of the installation, installation documentation, including "as fitted drawings", wiring schedule(s) and records of measurements and tests carried out should be provided for use during commissioning and handover of the system Location Verification: COMMENTARY ON 11.2 When installing DSDs it is important to carry out pre-installation checks to confirm that the actual conditions match those anticipated in the design specification Once the location of the DSD has been identified, humidity and temperature outside the duct should be assessed and checked against manufacturer s specifications. Any discrepancies should be referred back to the designer of the system If external conditions are suitable, air velocity, temperature and humidity inside the duct should be measured while the HVAC is running and checked against the DSD manufacturer s specifications. Any discrepancies should be referred back to the designer of the system. NOTE 1: To carry out these measurements; it will be necessary to provide access for instrumentation probes. This is likely to require drilling a test hole in one of the anticipated entry points of the DSD. NOTE 2: To be confident that the DSD will operate correctly it is necessary to make these measurements in several modes of operation of the HVAC, for example at maximum heating and maximum cooling. Issue 1.0 Page 18 of 35

19 11.3 Installation of Point type internal DSDs COMMENTARY ON 11.3 Point type internal DSDs are mounted within the duct itself. Consideration needs to be given on the means of rigidly mounting the detectors in the duct to ensure their correct operation under the mechanical stresses that may be encountered in the duct such as pressure and vibration. As point type internal DSDs are enclosed in the duct, consideration needs also be given to incorporating access facilities, such as a removable panel or door, for inspection and test during maintenance. The following recommendations apply specifically to the installation of point type internal DSDs: Each point type internal DSD should be mounted towards the centre of the duct using an appropriate stand-off in accordance with the manufacturer's instructions Point type internal DSDs should be mounted rigidly to withstand the pressure and resonant vibrations, in particular, those caused by air flow An access panel or door should be incorporated in the duct side walls to permit access to point type internal DSDs during installation and for routine maintenance inspection and test Installation of Point type external DSDs COMMENTARY ON 11.4 Point type external DSDs mounted in an enclosure with sampling tubes can be installed onto any wall of the duct unless otherwise restricted by the manufacturer s instructions. Point type external DSDs are usually fitted with a sampling tube and an exhaust tube. It is important that the manufacturer's instructions are followed when selecting the length of the sampling tube, the number of sampling holes needed and the means by which it is secured to the duct. The length of the exhaust tube is not usually a critical dimension and may vary from a stub to the full width of the duct. It is important not to confuse the sampling and exhaust tubes and to ensure that they are connected to the correct ports in the DSD. To ensure the correct operation of point type external DSDs, it is essential to avoid air leaks which may dilute or redirect smoke. It is important that gaskets and seals supplied with the DSD are fitted correctly to eliminate leaks. The following recommendations apply specifically to the installation of point type external DSDs: The enclosure of point type external DSDs should be mounted to the wall of the duct in accordance with the manufacturer's instructions When installing point type external DSDs, the following steps should be followed: a) select the appropriate sampling tube length for duct installation NOTE 3: Long sampling tubes, e.g. in excess of 900 mm, need extra support. This can be an internal strut or a hole in the opposite wall of the duct. b) secure the sampling tube to the inlet port on the duct enclosure ensuring that the holes or openings located along the length of the sampling tube face into the air flow; NOTE 4: Some DSDs may require an end-cap to be fitted to the sampling tube. NOTE 5: where not provided as part of the DSD design, consider providing an external indication of the orientation of the holes on the sampling tube. c) secure the exhaust tube to the outlet port on the duct enclosure d) if duct sampling tubes protrude through opposite side of duct, seal the opening around the tube on the outside of the duct with a suitable sealant e) prior to completing the installation, clean the duct enclosure, and check indicators for hole orientation After installing the point type external DSD, the differential pressure between the inlet and outlet ports of the enclosure, should be measured and checked against the manufacturer's specification. Issue 1.0 Page 19 of 35

20 NOTE 6: To be confident that the DSD will operate correctly it is necessary to make this measurement in several modes of operation of the HVAC, for example at maximum and minimum air flow Installation of Aspirated DSDs COMMENTARY ON 11.5 Aspirated DSDs are sited external to the duct with a sampling probe and an exhaust probe protruding into the duct at the point of detection. Extended pipework can be used to allow the ASD to be mounted in a remote location that is convenient for maintenance. Additionally, a remote test sampling point can be provided, which is closed during normal operation, for the convenience of maintenance testing. The design and orientation of the sampling and exhaust probes should follow the manufacturer's instructions but in general the orientation is less critical than with systems which do not have a fan to draw air samples through the detector. Furthermore, it is strongly recommended that the orientation of the holes is clearly marked on probes where they emerge from the duct to assist with maintenance. Where the aspirated DSD is sampling from a duct with high levels of contamination additional pipework or valves can be provided for the convenience of maintenance for example providing a blow-back arrangement system in a duct that forms part of a drying process producing high levels of dust/fibres. To ensure the correct operation of Aspirated DSDs, it is essential to avoid air leaks which may dilute or redirect smoke. It is important that appropriate gaskets and seals are fitted to eliminate leaks. The following recommendations apply specifically to the installation of Aspirated DSDs: Pipework running between the sampling probes and the ASD unit should be in accordance with EN The design, position and orientation of the sampling and exhaust probes should be in accordance with the manufacturer's instructions. NOTE 7: Long sampling probes, e.g. in excess of 900 mm, need extra support. This can be an internal strut or a hole in the opposite wall of the duct. NOTE 8: Correct orientation of the sampling and exhaust probes ensures that the flow through the ASD is largely independent of the flow rate in the duct. Incorrect orientation may lead to nuisance flow faults in the ASD as a result of the changing flow rates in the duct The orientation of the sampling holes should be clearly marked on the sampling and exhaust probes to assist with maintenance. A corresponding mark should be provided on the duct so that, if the probe is removed for maintenance, it is subsequently restored to the correct orientation External in-line components such as filters or water traps should be approved for use on the ASD. WARNING the uses of un-approved filters in the sampling pipework may inadvertently block the passage of smoke before there is an appreciable reduction in flow All penetrations into the duct should be carefully sealed using appropriate fittings, gaskets and/or sealants to ensure that the integrity of the duct is not compromised. 12 Commissioning and Handover COMMENTARY ON 12 Commissioning tests are carried out on all DSD systems when the HVAC systems are in their normal, intended running states. Appropriate commissioning tests also need to be performed after modifications and/or additions to a DSD system. The commissioning process comprises several stages the results of which are verified and recorded. These stages are: Inspection of Installation Power up/configuration Commissioning tests Signalling Issue 1.0 Page 20 of 35

21 After the DSD system has been successfully commissioned, it is necessary to undergo a formal system handover to the user or purchaser Commissioning The following recommendations apply to the commissioning stage: Inspection of installation The installation should be inspected to confirm that it has been installed correctly and conforms to the design documentation. In particular this inspection should cover the following: a) correct installation of the DSD against the manufacturer's instruction with particular attention to: 1) mechanical mounting 2) configuration of any pipe and sampling tubes (including sample hole sizes and positions) 3) seals and/or filters 4) internal wiring b) confirmation that smoke entry points are not obstructed c) correct installation of all external wiring d) correct sizing of power supplies e) re-instatement of ducting to normal operating condition Duct air flow verification COMMENTARY ON For certain types of DSD it may be necessary to verify that the air flow in the duct is within the parameters specified for that DSD. This may be achieved by direct measurement of the air velocity or by measurement of pressure differential For point external type DSDs which rely on the Venturi effect, air flow through the detector should verified by measuring the static pressure difference between the inlet an outlet tubes. NOTE 1 Pressure difference measurement may be achieved by using a manometer or pressure differential gauges For point internal and ASD type DSDs the air velocity should be measured inside the duct at the smoke entry location to verify that it is within the DSD manufacturer's recommendations For other DSD types reference should be made to manufacturer's instructions Initial power up COMMENTARY ON Before commissioning tests can be carried out it is necessary to ensure that the DSD system powers up normally and any site-specific equipment configuration has been implemented Where applicable, prior to carrying out any functional and performance tests the DSD equipment should be configured for: a) detector sensitivity settings. b) alarm and fault delay periods c) airflow monitoring parameters d) any other required configuration settings Commissioning tests COMMENTARY ON Before these tests are carried out it is important to ensure that the air-handling system is in its normal operational state. Issue 1.0 Page 21 of 35

22 In commissioning testing there are three distinct stages that need to be covered. Two or more steps may be performed in parallel, for example introducing smoke into the duct in sufficient quantity to trigger an alarm could test steps a), b) and c) Commissioning instructions from the product supplier should be followed and should include each of the following steps: a) Check that the DSD responds to a smoke (or simulated smoke) stimulus by signalling an alarm condition to the CIE or local control electronics b) Check that the detector triggers the appropriate system response as specified c) For DSD systems that are designed to conform to a specific performance requirement, additional tests should be carried out as may be agreed with relevant interested parties NOTE 2: For example where a high sensitivity DSD is required, tests according to BS 6266 may be applied All signalling between the DSD and associated control and indicating system(s), for example the fire alarm system CIE, should be verified in accordance with the design by initiating each applicable alarm and fault condition System Handover During the commissioning all results should be recorded. These along with all configuration data should be submitted as part of the commissioning certificate in accordance with local Standards or Code of Practice (e.g. BS ). 13 Maintenance COMMENTARY ON 13 Field service and maintenance of a DSD is essential to ensure that the equipment remains in its correct operating condition. It is important that the tests performed demonstrate that the equipment is able to detect smoke and trigger appropriate action as intended when it was designed, installed and commissioned. The application of maintenance procedures although they may be different are equally important to all the types of DSDs covered in this Code of Practice: point external, point internal, aspirating smoke detectors or other smoke detection arrangements such as beam smoke detectors. Recommendations concerning the required procedure for each of the detection types are given in this clause. The following recommendations apply to the maintenance stage: 13.1 Maintenance instructions given by the supplier should be followed. These should include the four stages defined NOTE 1: There are deemed to be four distinct stages that needs to be covered during maintenance testing of a DSD. Two or more stages may be performed in parallel for example introducing smoke into the duct in sufficient quantity to trigger and alarm might test steps 2, 3 and 4 in Maintenance instructions from the product supplier might include steps 1 to 4 defined in Before starting any maintenance activities: a) appropriate authorities should be notified that the smoke detection system will be temporarily out of service b) the zone or system under test should be disabled to prevent unwanted alarms c) Any changes to the system and/or the environment in which it is used should be identified, recorded in the log book and its effect on the performance of the system assessed 13.3 During maintenance testing the following should be checked and/or measured: a) measure the airspeed in the duct in order to determine that it is still within the range for which the DSD was designed and the detectors specified b) check that smoke from the duct can reach the detector. For each smoke detection technology, this may require different checks and procedures, as follows: Issue 1.0 Page 22 of 35

23 1) for point external detectors: i) check the detector housing, pipe-work and all seals and fixings for damage or degradation ii) check that the sampling probes/tubes are not blocked or damaged - if they are removed during this check, after re-insertion, the airflow sampling from the duct should be checked for direction iii) check that there is sufficient airflow sampling from the duct and through the detector by measuring the air movement in the duct housing or the differential pressure between the sampling tubes - this should be within the stated range of pressure for the installation 2) for point internal detectors: i) check that the detector is securely mounted in the airstream in the duct as intended 3) for aspirating smoke detectors: i) check that the sampling probes/tubes are not blocked or damaged - if they are removed ensure they are replaced in the original configuration and orientation ii) check that there is no air leakage around the duct sampling probes/tubes where they enter the duct iii) check all seals and fixings to the duct and ensure that there are no holes in the duct or pipe-work iv) check that the sampling points are not blocked or partially obscured 4) For other smoke detection technologies: i) check that the sensor/detection technology used is able to receive the smoke from the airflow in the duct so that the required response is achieved; ii) refer to the manufacturer's instructions for further checks that are required. 5) Beam smoke detector: i) check that the beam is not obscured or disabled from sensing the presence of smoke ii) refer to the manufacturer's instructions for further checks c) Check that the detector is able to detect the smoke which reaches it by introducing a smoke (or simulated smoke) stimulus to the detector and verifying that the detector respond to that stimulus by signalling an alarm condition to the CIE or local control electronics d) Verify that the detector triggers the appropriate alarm actions or other response as intended for the specific system under test NOTE 2: The actual response of the system will depend on its design and configuration but the tests demonstrates that the system responds correctly to the alarm condition, as per the system design requirements e) Verify that the current consumption of the DSDs against previous readings and that they are within specification 13.4 Following any maintenance tests on the DSD system, the test log should be completed and the system re-instated to its normal mode of operation. If the tests were carried out as part of the commissioning of a DSD system, handover shall be conducted according to BS for any fire system. 14 User Responsibilities COMMENTARY ON 14 Issue 1.0 Page 23 of 35