System Sensor Application Guide for Proper Use of Smokes in Duct Applic

Guide For Use SENSOR Manuals Online OF CONTENTS 1 2 OF OPERATION 4 5 Detection Feature 5 Application 5 SMOKE DETECTORS VS SPOT TYPE SMOKE DETECTORS 6 6 Height 6 Air Velocity 7 7 Environments 8 REQUIREMENTS 9 9 and Spacing 9 9 13 Manuals Online purpose of this guide is to provide information on the proper utilization of beam smoke detectors in and property protection applications This guide briefly summarizes the principles of of projected beam smoke detectors their design requirements and practical applications for use as a component of an automatic fire alarm system smoke detectors can be important components of a well designed automatic fire alarm system of their unique capabilities beam smoke detectors can overcome many of the problems and of spot type smoke detectors in some applications This guide was developed to help the fire designer gain an understanding of the beam smoke detector capabilities and limitations and they differ from spot type smoke detectors equipment from different manufacturers has varying specifications and listings the information in guide is general in nature and should not be used as a substitute for the manufacturer or code requirements Manuals Online device which gives a visible or audible indication of the condition or status such as normal trouble alarm of a smoke detector or system GAIN CONTROL AGC ability of a beam smoke detector to compensate for light signal degradation due to dust or dirt of compensation is limited to insure that the detector is still sensitive to slow smoldering fires SMOKE DETECTOR PROJECTED BEAM SMOKE DETECTOR device which senses smoke or smoke and heat by projecting a light beam from a transmitter across protected area to a receiver that monitors the light signal Smoke and or heat entering the beam will decrease the light signal causing an alarm RANGE distance between the transmitter and receiver Where mirrors are used to direct the beam the total range includes the distance between the mirrors and the transmitter and receiver COVERAGE area in which a smoke detector or heat detector is considered to effectively sense smoke and or This area is limited by applicable listings and codes inclusion of a device in a list published by a recognized testing organization indicating that the has been successfully tested to meet the accepted standards CUMULATIVE OBSCURATION reduction of the ability of light to travel from one point to another due to the presence of solids gases or aerosols CUMULATIVE OBSCURATION is a combination of the density of these light particles per foot and the linear distance which these particles occupy i e smoke density the linear distance of the smoke field device in a projected beam smoke detector system which monitors the signal level of the light is sent by the transmitter ability of a smoke detector to respond to a given level of smoke solid and gaseous airborne products of combustion COLOR relative lightness or darkness of smoke ranging from invisible to white to gray to black DENSITY relative quantity of solid and gaseous airborne products of combustion in a given volume DETECTOR device which senses smoke and or heat at its location only Spot type detectors have a defined area coverage Manuals Online effect which occurs when smoke which is hotter than the surrounding air rises until equal to the of the surrounding air causing the smoke to stop rising PROJECTOR device in a projected beam smoke detector which projects the light across the protected area FILTERS panel of glass or plastic having a known level of obscuration which can be used to test the proper level of a beam smoke detector CONDITION status of a device or system which impairs its proper operation i e open circuit on an initiation The notification of a trouble condition indicated on a control panel or annunciator is a Manuals Online OF OPERATION beam smoke detectors consist of a transmitter that projects an infrared beam across the area to a receiver containing a photosensitive cell which monitors the signal strength of the beam The detector works on the principle of light obscuration The photosensitive element of the smoke detector sees light produced by the receiver in a normal condition The receiver is to a preset sensitivity level based on a percentage of total obscuration This sensitivity level determined by the manufacturer based on the length of the beam the distance between the and receiver Typically more than one setting is available for selection by the installer on the length of the beam used in a given application For UL listed detectors the sensitivity must comply with UL Standard 268 Detectors for Fire Protective Signaling Systems PROJECTOR PATH OR BEAM RANGE 1 transmitter on some units may be powered independently from the receiver which can greatly wiring runs and therefore installation cost Since battery back up is required for fire alarm battery back up would be required for the transmitter whether it is powered from the panel or spot type photoelectronic smoke detectors beam smoke detectors are generally less response to the color of smoke Therefore a beam smoke detector may be well suited to applications for spot type photoelectronic detectors such as applications where the anticipated fire would black smoke Beam smoke detectors do require visible smoke and therefore may not be as as ion detectors in some applications smoke detectors are sensitive to the cumulative obscuration presented by a smoke field This obscuration is created by a combination of smoke density and the linear distance of the field across the projected light beam Cumulative obscuration then is a measure of the of light blockage the sudden and total obscuration of the light beam is not a typical smoke signature the detector see this as a trouble condition not an alarm This threshold is typically set by the manufacturer at a level which exceeds 90 to 95 total obscuration This minimizes the possibility of an alarm due to the blockage of the beam by a solid object such as a sign or ladder being placed in the beam path small slow changes in the quality of the light source also are not typical of a smoke signature changes may occur because of environmental conditions such as dust and dirt accumulation on transmitter and or receiver optical assemblies These changes are typically compensated for by automatic gain control AGC When th