System Sensor Duct Application Smokes

C1C1 Guide Application Detectors Manuals Online Application Smoke Detectors 1999 Edition 1 of Terms 2 3 of Smoke in HVAC Systems 4 Smoke Detection Equipment 5 Air Handling Systems 6 Duct Detection Systems are Used to Control Smoke 7 for Duct Smoke Detector Application and Installation 8 Maintenance and Service of Detectors for Use in Ducts purpose of this guide is to provide much needed information concerning the use of smoke detectors in duct applications Duct mounted smoke are designed to provide a specific type of protection that cannot be by any other type of system However there has been a tendency to these devices in the past attempting to use them as a substitute for an warning smoke detection system This fact coupled with new methods of smoke in ducts has prompted the writing of this industry guide Fire Engineers Mechanical and Electrical Engineers Fire Alarm System and installers should the contents both educational and informative information is intended as a technical guide as distinct from mandatory Manuals Online U C T A P P L I C A T I O N S M O K E D E T E C T O R S 1 Glossary of Terms Sampling Detector extremely sensitive smoke detection device that can sample test and the amount of particle concentration within an air sample Smoke Detector device that will detect visible or invisible particles of combustion Also called spot type detector cooling or heating element made of pipe or tubing direct expansion using the direct refrigeration method volume of flow cubic feet per minute per minute unit velocity of air flow valve or plate regulating the flow of air or other fluid multiple louver damper having a number of adjustable blades used to vary the volume of air through a confined section by varying the cross sectional area passageway made of sheet metal or other suitable material not necessarily used for conveying air or other gas at low pressures Smoke Detector device located within the duct protruding into the duct or located outside the that detects visible or invisible particles of combustion flowing within the Actuation of the device may allow operation of certain control functions Tube a round tube that provides a path for sampled air to return from the device to the duct air moving device comprising a wheel or blade and a housing or ori plate device to add moisture to the air Manuals Online Y S T E M S E N S O R 1 of Terms of Water unit of pressure equal to the pressure exerted by a column of water at a of 4.0 39.2 Sampling Tube a round tube with holes that collects air from the duct and brings it the detection device Detector smoke detector using the principle of ion flow within a chamber to detect and invisible particles of combustion within a size range normally as a result of fire Beam Detector smoke detection device that operates on the smoke obscuration principle Magnehelic Gauge for reading static pressures in air systems Detector smoke detector using the principle of optical detection of visible particles combustion Tube device used to measure the total pressure of a fluid stream It is essentially tube attached to a manometer at one end and pointed upstream at the other normal force exerted by a homogenous liquid or gas per unit of area on wall of a container Differential pressure difference usually specified in inches of water between two points a duct Exhaust duct which is used to return the air to the HVAC processing center conditioning Tube a round tube with holes that collects air from the duct and brings to the detection device Detectors device used to automatically sense the presence of particles of combustion Manuals Online U C T A P P L I C A T I O N S M O K E D E T E C T O R S 1 of Terms phenomenon where smoke or other gases travel in layers at different levels the duct rather than being evenly distributed throughout the duct Duct duct which distributes conditioned air i e cooled heated cleaned etc device used to measure air velocity Principle tube with a narrow throat a constriction that increases the velocity and the pressure of the liquid or gas passing through it creating a partial immediately after the constriction in the tube The vacuum created a sucking effect eduction and a venturi is commonly used to introduce a such as a regenerant or gas such as air into a flowing water stream Manuals Online Y S T E M S E N S O R 2 Purpose of Duct Smoke Detection National and local safety standards and codes recognize the ability of air duct to transfer smoke toxic gases and flame from area to area Sometimes can be of such quantity as to be a serious hazard to life safety unless are shut down and dampers are actuated The primary purpose of duct detection then is to prevent injury panic and property damage by reducing spread recirculation of smoke Duct smoke detection can also serve to the air conditioning system itself from fire and smoke damage and can used to assist in equipment protection applications for example in the duct work of mainframe computers and tape drives more important is the identification of what duct smoke detection is not for rather than what it is is not a substitute for an area smoke detector is not a substitute for early warning detection is not a replacement for a building regular fire detection system 90A supports this by stating provided by the installation of detectors and other related requirements is intended to prevent the of smoke through the supply air duct system and preferably to a signi quantity of smoke to the outside Neither function however guarantee either early detection of fire or the detection of smoke concentra prior to dangerous smoke conditions if smoke movement is other than the supply air system 72 States that are installed in the air duct system shall not used as a substitute for open area protection of smoke laden air by clean air from other parts of the building or by outside air intakes may allow high densities of smoke in a single with no appreciable smoke in the air duct at the detector location may not be drawn from open areas when air conditioning or ventilating are shut down Area smoke detectors are the preferred means of controlling smoke spread since Duct smoke detectors can only detect smoke when smoke laden air is circulating in ductwork Fans may not be running at all times such as during cyclical or during temporary power failure Duct smoke detectors sample great volumes of air from large areas of coverage cannot be expected to match the detection ability of area detectors Dirt contaminated air filters can restrict air flow causing a reduction in the effectiveness of the duct smoke detectors NFPA 90A 1996 Section 4 4.2 NFPA 72 1996 Section 5 11.2 Manuals Online U C T A P P L I C A T I O N S M O K E D E T E C T O R S 2 NFPA 90A1 for the Installation of Air Conditioning and Ventilating specifies that Detectors listed for use in air distribution shall be located Downstream of the air filters and ahead of any branch connections in air systems having a capacity greater than 2,000 cfm 944 L sec At each story prior to the connection to a common return and prior to any or fresh air inlet connection in air return systems having a capacity than 15,000 cfm 7080 L sec and serving more than one story No 1 system smoke detectors are not required when the entire space served by air distribution system is protected