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System Sensor A05-1003-002 Smoke Alarm User Manual

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1. am a a 20 5 ft 41 ft 82 ft Figure 21 Detector Placement in Hallways lating or air conditioning HVAC system creates arti ficial hot or cold air layers in a room the layers may affect the flow of smoke to the detectors Uninsulated Roofs Uninsulated roofs present special placement problems Air movement toward ceiling detectors is not impeded when the outside tempera ture is cool but stratification can occur when outside temperature is warm or hot or when the roof is heat ed by the sun on bright sunny days Although true thermal barriers are not present in many installations smoke tests should be run in factories or warehouses with metal roofs on warm sunny days to determine whether such a thermal barrier exists Peaked or Sloped Ceilings Peaked or sloped ceilings can foster air stratification Codes may specify spacing detectors by using horizontal spacing from the peak of the roof or ceiling For instance if the specified dis tance from the peak is 3 feet 1 m the dis tance is measured on the base of the right triangle formed by a vertical line dropped from the peak of the roof with the roof incline as the hypotenuse Additional detec tors are installed on the selected spacing using the horizontal distance not the distance along the incline of the ceiling See Figure 22 S Detector Spacing Figure 22 Detector Spacing Layout Sloped Ceilings peaked type S 2 10 ft
2. Testing laboratories test smoke detectors control panels and other components of fire alarm systems to verify con formance with NFPA requirements and their own stan dards Equipment that passes their tests are identified by a label and or listing Underwriters Laboratories Inc UL 333 Pfingsten Road Northbrook Illinois 60062 1655 Scott Boulevard Santa Clara California 95050 1285 Walt Whitman Road Melville New York 11747 12 Laboratory Drive P O Box 13995 Research Triangle Park North Carolina UL publishes an annual directory listing fire protection equipment which bear the UL label Its standards which apply to smoke detectors are UL 217 Single and Multiple Station Smoke Detectors UL 268 Smoke Detectors for Fire Protection Signaling Systems UL 268A Smoke Detectors for Duct Applications UL 864 Standard for Control Units for Fire Protective Signaling Systems Factory Mutual Research FM 1151 Boston Providence Turnpike P O Box 9102 Norwood Massachusetts 02062 FM publishes an annual report listing fire protection equip ment which bears its label SYSTEM Industry Publications NEMA Guide for Proper Use of Smoke Detectors in Duct Applications NEMA Training Manual on Fire Alarm Systems NEMA Guide to Code Requirements for Fire Protective Signaling and Detection Systems NEMA Guide for proper Use of System Smoke Detectors SENSOR Manufacturer s Publications The manufacturer of the smoke detectors bei
3. Figure 9 Light Obscuration Detector with Smoke Smoke Detector Design Considerations Smoke detectors are based on simple concepts but certain design considerations need to be observed They should produce an alarm signal when smoke is detected but should minimize the impact of an unwanted signal which can arise from a variety of causes In an ionization detec tor dust and dirt can accumulate on the radioactive source and cause it to become more sensitive In a photoelectric detector light from the light source may be reflected off the walls of the sensing chamber and be seen by the photo sensitive device when no smoke is present The entrance of insects dirt drywall dust and other forms of contamina tion into the sensing chamber can also reflect light from the light source onto the photosensitive device Electrical transients and some kinds of radiated energy can affect the circuitry of both ionization and photoelectric smoke detectors and be interpreted by the electronic cir cuitry to be smoke resulting in nuisance alarms The allowable sensitivity ranges for both types of detectors are established by Underwriters Laboratories Inc and all are verified by their performance in fire tests Regardless of their principle of operation all smoke detectors are required to respond to the same test fires Considerations in Selecting Detectors The characteristics of an ionization detector make it more suitable for detection of fast
4. O Detector may be placed anywhere in shaded area APPLICATIONS GUIDE SYSTEM e Alternate Detector Mounting Mounting alternate detectors up to 3 feet 1 m below the ceiling can increase detection of small or smoldering fires when the possibility of air stratification exists Figure 23 illustrates such an installation Specific designs for such an alternate detection should be based upon an engineering survey Heating Ventilating and Air Conditioning HVAC effects on air flow and air stratification should be determined and considered when planning detector placement In rooms where forced air ventilation is present detectors should not be located where air from supply diffusers could dilute smoke before it reaches the detector This may require additional detectors because placing detectors only near return air openings may leave the balance of the area with inadequate protection especially when the Heating Ventilating and Air Conditioning HVAC system is not operating Detectors placed in an above ceiling air handling space should not be used as a substitute for open area pro tection because smoke may not be drawn into the air handling space when the ventilating system is shut down The detector will be less responsive to a fire condition in the room below than a detector located on the ceiling of the room below due to dilution and fil tering of the air in the air handling space before the smoke reaches a detector See the dis
5. or localized heating or cooling from heating ventilating and air conditioning systems and extensive variability in the value and combustion char acteristics of building contents The following are suggest ed techniques for dealing with some of the special detector spacing problems e Solid joist and beam construction Per NFPA 72 1996 solid joists are to be considered equivalent to beams for smoke detector spacing guidelines For ceiling heights of 12 ft 3 66 m or lower and beam depths of 1 ft 0 3 m or less smooth ceiling spacing running in the direction parallel to the run of the beams is to be used and 1 2 the smooth ceiling spacing is to be used in the direction perpendicular to the run of the beams Spot type detectors may be located either on the ceil ing or on the bottom of the beams For beam depths exceeding 1 ft 0 3 m or for ceiling heights exceeding 12 ft 3 66 m detectors are to be located on the ceil ing in every beam pocket If the beamed ceiling is also sloped use the spacing determined for flat beamed ceilings Use the average height over the slope as the ceiling height in such cases Note that by definition in NFPA 72 ceilings are to be considered smooth unless the beams or joists are more than 4 in 0 1 m in depth High storage racks Multi level storage racks present special problems for early fire detection Developing fires especially smoldering fires on the lower levels of the racks may not be s
6. Authorities Having Jurisdiction AHJ s should be followed In partic ular the most current version of NFPA 72 for installation and testing of systems is a key element in the effectiveness of smoke detection systems Section 1 Standards That Apply NFPA Codes and Standards NFPA publishes standards for the proper application instal lation and maintenance of automatic smoke detectors The principal codes and standards that should be reviewed before specifying or installing automatic smoke detectors are listed below National Fire Protection Association NFPA Batterymarch Park Quincy Massachusetts 02269 9101 NFPA publishes codes and standards concerning all phas es of fire protection Among those which directly concern automatic smoke detectors are NFPA 70 National Electrical Code NFPA 72 National Fire Alarm Code NFPA 72 covers minimum performance location mount ing testing and maintenance requirements of automatic fire detectors NFPA 90A Standard for the Installation of Air Conditioning and Ventilating Systems NFPA 92A Smoke Control Systems in Malls Atria and Large Areas NFPA 90A and 92A provide information for the use of smoke detectors in ducts of HVAC systems and smoke con trol systems NFPA 101 Life Safety Code NFPA 101 specifies the requirements for smoke detection in both new and existing buildings depending on the type of occupancy Building and Fire Codes There are three independ
7. Notification Appliance An electromechanical appliance that converts energy into audible or visible signal for perception as an alarm signal Alarm Signal A signal indicating an emergency requiring immediate action such as an alarm for fire from a manual box a waterflow alarm or an alarm from an automatic fire alarm system or other emergency signal Alarm Verification Feature A feature of automatic fire detection and alarm systems to reduce unwanted alarms wherein automatic fire detectors must report alarm conditions for a minimum period of time or confirm alarm conditions within a given time period after being reset to be accepted as a valid alarm initiation signal Annunciation A visible and or audible indication of system status Automatic Fire Alarm System A system of controls initiating devices and alarm signals in which all or some of the initiating circuits are activated by automatic devices such as smoke detectors Class A Circuit Loop An arrangement of supervised initiating device signaling line or indicating appliance circuits that prevents a single open or ground on the installation wiring of these circuits from causing loss of the system s intended function Class B Circuit Loop An arrangement of supervised initiating device signaling line or indicating appliance circuits which does not pre vent a single open or ground on the installation wiring of these circuits from causing loss of the system s
8. a fire alarm box smoke heat or flame sensing device sprinkler waterflow alarm switch or similar device or equipment to a control panel or any similar device or equipment which when activated caus es an alarm to be indicated or retransmitted An Initiating Device Circuit Loop is a circuit to which automatic or manual signal initiating devices are connected where the signal received does not identify the individual device operated Initiating Device Any manually operated or automatically operated equip ment which when activated initiates an alarm through an alarm signaling device Intelligent Analog Smart System Smoke Detector A system smoke detector capable of communicating infor mation about smoke conditions at its location to a control unit This type of detector typically communicates a unique identification address along with an analog data signal which indicates the level of smoke at its location lonization Smoke Detector An ionization smoke detector has a small amount of radioactive material that ionizes the air in the sensing chamber thus rendering it conductive and permitting a current to flow between two charged electrodes This gives the sensing chamber an effective electrical conductance When particles of combustion enter the ionization area they decrease the conductance of the air by attaching themselves to the ions causing a reduction in mobility When the conductance is less than a predetermined leve
9. alarm evacuation signal described in ANSI S3 41 Audible Emergency Evacuation Signals Situations Where Other Types of Detectors May Be Used In certain circumstances where standard smoke detectors are unsuitable special purpose detectors such as flame detectors heat detectors and other detection devices may be used The application of these special types of detectors should be based on an engineering survey and used in accordance with the manufacturer s installation instructions provided Smoke Detectors Have Limitations Smoke detectors offer the earliest possible warning of fire They have saved thousands of lives in the past and will save more in the future Nevertheless smoke detectors do have limitations They may not provide early warning of a fire developing on another level of a building A first floor detector for example may not detect a second floor fire For this reason detectors should be located on every level of a building In addition detectors may not sense a fire developing on the other side of a closed door In areas where doors are usually closed detectors should be locat ed on both sides of the door As already indicated detectors have sensing limitations Ionization detectors are better at detecting fast flaming fires than slow smoldering fires Photoelectric smoke detectors sense smoldering fires better than flaming fires Because fires develop in different ways and are often unpredictable in their
10. dia grams on the following page should be considered as typi cal initiating device circuits utilizing smoke detectors They are offered to illustrate proper and improper installation wiring and termination techniques Since there are always exceptions to typical installation drawings experienced installers use the primary rule of installation wiring Follow the manufacturer s instructions and meet the local codes Figure 12 illustrates improper wiring of smoke detector A This wiring method is referred to as T tapping This com mon installation error is often made in riser wiring as well as single floor wiring The smoke detector may operate properly under alarm conditions If it becomes disconnect ed from the installation wiring loop beyond the T tap however the detector would not function and no trou ble condition would occur NOTE T tapping may be permitted with some intelligent fire alarm systems Refer to manufacturer s recommendations Figure 13 illustrates the correct installation wiring method for smoke detectors None of the connections can be bro ken without opening the circuit causing loss of supervi sion and the fire alarm control panel to indicate trouble Smoke detectors should be connected to supervised instal lation wiring in a manner that ensures electrical supervision of the device Removal of a detector from its associated ini tiating circuit should cause the loop to o
11. fire deaths The sooner a fire is detected the better the chances are for survival A potential problem with smoke detectors is unwanted alarms that often result in people being desensitized to the alarm system or in severe cases dis connecting the system This is an industry wide problem that in most cases is caused by improper application installation and maintenance of smoke detectors It is hoped that the information in this guide will be used by those involved with the application installation and maintenance of fire alarm systems to minimize these problems A P P L CAT 1 ON S G UIDE SYSTEM The purpose of this guide is to provide information con cerning the proper application of smoke detectors used in conjunction with fire alarm systems It outlines basic prin ciples that should be considered in the application of early warning fire and smoke detection devices Operating char acteristics of detectors and environmental factors which may aid delay or prevent their operation are presented Introduction Fire protection engineers mechanical and electrical engi neers fire service personnel fire alarm designers and SMOKE DETECTORS installers should find the contents both educational and informative Though this information is based upon industry expertise and many years of experience it is intended to be used only as a technical guide The requirements of applicable codes and standards as well as directives of the
12. flaming fires that are charac terized by combustion particles in the 0 01 to 0 4 micron size range Photoelectric smoke detectors are better suited to detect slow smoldering fires that are characterized by particulates in the 0 4 to 10 0 micron size range Each type of detector can detect both types of fires but their respec tive response times will vary depending on the type of fire Because the protected buildings normally contain a variety of combustibles it is often very difficult to predict what size particulate matter will be produced by a developing fire The fact that different ignition sources can have dif ferent effects on a given combustible further complicates the selection A lighted cigarette for example will usually produce a slow smoldering fire if it is dropped on a sofa or bed However if the cigarette happens to fall upon a news paper on top of a sofa or bed the resulting fire may be characterized more by flames than by smoldering smoke The innumerable combustion profiles possible with vari ous fire loads and possible ignition sources make it difficult to select the type of detector best suited for a particular application SYSTEM SENSOR For more information see NFPA 72 1999 paragraphs A 2 3 6 1 2 A 2 3 6 1 1 A 2 3 6 1 2 a and A 2 3 6 1 2 b NFPA 72 requirements also dictate that alarm notification appliances including smoke detectors with built in sounders produce the 3 pulse temporal pattern fire
13. for troubleshooting and locating purposes SYSTEM SMOKE DETECTORS TYPICAL INITIATING gt DEVICES INITIATING DEVICE CIRCUIT ZONE 1 TROUBLE INITIATING DEVICE CIRCUIT RETURN ALARM FIRE ALARM CONTROL UNIT PRIMARY POWER SUPPLY Figure 11 2 Wire Detectors Style D Class A Circuit Fire Safety Functions Often smoke detectors are utilized to control ancillary equipment Most detectors used in releasing service have auxiliary relay contacts which are directly connected to the system or device to be controlled Care should be taken to ensure that detectors utilized in such a manner are approved for releasing service A few of the typical appli cations are as follows e To control the flow of smoke in air handling and air conditioning systems e To release doors to contain smoke in a fire situation e To release locks to allow exit in a fire situation e To capture and recall elevators in a fire situation e To activate a suppression system Spacing and placement requirements for detectors used in releasing service may be different from detectors used in conventional open area applications It is recommended that 4 wire detectors be used in these situations because depending on the control panel and detectors used more than one detector relay on a circuit may not receive enough power from the 2 wire circuit to operate during alarm Smoke Detector Installation Wiring Installation Guidelines All fire
14. growth neither type of detector is always best A given detector may not always provide sig nificant advance warning of fires when fire protection prac tices are inadequate nor when caused by violent explo sions escaping gas improper storage of flammable liquids such as cleaning solvents etc Section 3 Wiring Supervision Typical System The initiating circuits that con Layout nect smoke detectors to a con trol panel should be super vised so that a fault trouble condition that could interfere with the proper operation of the circuit will be detected and annunciated Smoke detectors are generally categorized as either 2 wire or 4 wire detectors Two wire detectors derive their power directly from the same fire alarm control panel alarm initi ating device circuit over which they report an alarm Because of their dependency on the initiating circuit 2 wire detectors must be tested and listed for compatibility with the control panel to be used to ensure proper operation Four wire detectors are powered from a separate pair of wires and like the 2 wire detector apply an electrical short across the associated alarm initiating device circuit to transmit an alarm Figure 10 Because they do not derive power from the alarm initiating device circuit electrical compatibility is predicated upon the operating parameters of the power supply to which the detectors are connected and not the initiating circuit Supervision of the power
15. intended function Combination Smoke Detector A smoke detector that combines two or more smoke or fire sensing technologies Detector Coverage The recommended maximum distance between adjacent detectors or the area that a detector is designated to protect Drift Compensation The capability of a detector to automatically adjust its alarm sensitivity to compensate for any changes over time in the factory settings for smoke and or fire detection In analog systems this may be done by the panel End of Line A device such as a resistor or diode placed at the end of a Class B wire loop to maintain supervision End of Line Relay Device used to supervise power for four wire smoke detectors and installed after the last device on the loop False Alarms An unwanted alarm caused by non smoke contaminants such as dust or insects Fire A chemical reaction between oxygen and a combustible material where rapid oxidation results in the release of heat light flame and or smoke Flame Detector A device that detects the infrared ultraviolet or visible radiation produced by a fire Four wire Smoke Detector A smoke detector which initiates an alarm condition on two separate wires initiating loop apart from the two power leads Heat Detector A device that detects abnormally high temperature or rate of temperature rise Initiating Circuit A circuit which transmits an alarm signal initiated manu ally or automatically such as
16. or similar area and shall not actuate the building fire alarm system unless otherwise permitted by the authority having jurisdiction Section 9 6 1 5 states All systems and com ponents shall be approved for the purpose for which installed In addition to possible code noncompliance the following deficiencies would exist in a series of residential smoke detectors connected in a system mode e Since the system is not supervised vandals or others could disconnect a detector or the entire system leav ing a building without protection The residents would be unaware of this serious life threatening condition e Residential smoke alarms do not latch in alarm In other words the smoke alarm self resets One smoke alarm in alarm will sound all the smoke alarms con nected together It would be difficult to identify or locate a specific smoke alarm that initially put the sys tem into alarm after the alarm condition was cleared System detectors latch in alarm They do not reset until power is momentarily disconnected This makes it conven ient to identify the location of a detector that caused the control panel to alarm In addition system detectors are specifically designed to connect to a panel Two wire detec tors require a UL compatibility review to verify that the detector and panel operate together A typical life safety fire protection system for an apartment complex would be SMOKE DETECTORS to use system detectors and man
17. products that either remain at the site of burn ing such as ash or scatter as volatile products resulting from the chemical process of a fire Photoelectric Smoke Detector In a photoelectric light scattering smoke detector a light source and a photosensitive sensor are so arranged that the rays from the light source do not normally fall on the pho tosensitive sensor When smoke particles enter the light path some of the light is scattered by reflection and refrac tion onto the sensor causing the detector to respond Projected Beam Smoke Detector In a projected beam detector the amount of light transmit ted between a light source and a photosensitive sensor is monitored When smoke particles are introduced into the light path some of the light is scattered and some absorbed thereby reducing the light reaching the receiver causing the detector to respond Rate of rise Heat Detector A device which will respond when the temperature rises at a rate exceeding a predetermined amount usually 15 per minute Remote Maintenance Condition NFPA 72 listed method of providing annunciation at the control unit that the smoke detector is outside of its listed sensitivity Smoke Detector A device that detects the visible or invisible particles of combustion SMOKE DETECTORS Smoothing Algorithms A method of smoothing out a detector s interpretation of sudden short duration increases in obscuration within the sensing cham
18. recommended testing and maintenance intervals and procedures and a sample Detector Maintenance Log page Maintaining a complete file of information on the alarm system in a readily accessible location This file should include specifications and installation instruc tions for the detectors control panel and auxiliary devices wiring diagrams and wire location informa tion and the manufacturer s recommendations for iso lating the detection system wiring from other electrical wiring to prevent interference and unwanted alarms Making certain that maintenance personnel or con tractors working on the building s electrical systems are given copies of the alarm system wiring layout and locations so that potential interference from other wiring systems can be prevented by proper insulation and spacing during installation Keeping accurate records of installation and modifica tions to all other building electromechanical systems that could cause interference with the alarm system including updating schematics wiring layouts and wiring location information whenever changes are made so that problems can be promptly found and eliminated e Making a record of everything done during investiga tion of a series of alarms indicating a problem exists A P P L CAT 1 ON S GJ ity Dis iE SYSTEM If assistance must be sought from the installer or man ufacturer there will be an indication of the tests that have already been done by th
19. termination supervises all wiring to Smoke Detector the point at which it connects to the detector Figure 17 shows an incorrect pigtail connec tion This is a form of T tapping discussed earlier Note that the conductor between the wire nut or splice and the detector is unsu Figure 16 Pigtail Connections Correct Wiring Method F Wire Nut pervised and could be cut or disconnected without resulting in a trouble signal Wireless Systems Wireless smoke detectors do not require any field wiring as the power for the initiating devices is contained and incorporated within the device Removal of a wireless smoke detec Smoke Detector tor initiates a distinct tamper or trouble signal Follow the instructions in the manufacturer s installation manual for wireless systems Installation Do s and Don ts Do e Verify that 2 wire smoke detectors to be used have been tested and UL listed for compatibility with the equipment to Figure 17 Pigtail Connections Incorrect Wiring Method which they are connected If necessary contact the manufacturer for this informa tion Locate any end of line devices electrically at the end of the circuit beyond all initi ating devices not at the control unit except in a Class A installation e Use caution when utilizing 2 wire detec tors with integral relays because they SMOKE DETECTORS may require more power than the ini
20. to 4 wire detectors is mandated through the use of an end of line power supervision relay When power is on the relay contacts of the end of line relay are closed and connected in series with the end of line resistor beyond the last initi ating device Loss of power at any point in the power sup ply circuit will cause the relay to de energize and a trouble condition to occur on the initiating circuit NOTE Refer to the fire alarm control panel manufacturer s operating manual to determine the ability of a specific initi ating circuit to react in a Class B or Class A fashion NFPA 72 now classifies initiating device circuits by Style and Class Style B is an example of a Class B circuit Style D is an example of a Class A circuit Class B Circuits Class B circuits differentiate between short circuits across the loop alarm and opens on the loop trouble Supervision of this circuit is accomplished by passing a low current through the installation wiring and an end of line resistor Increases or decreases in this supervisory current are monitored by the fire alarm control panel and will cause alarm or trouble conditions respectively to be indi cated A single open in a Class B circuit disables all devices electrically beyond the open END OF LINE RESISTOR TYPICAL INITIATING DEVICES INITIATING DEVICE CIRCUIT ZONE 1 TROUBLE ALARM FIRE ALARM CONTROL UNIT PRIMARY POWER SUPPLY
21. Figure 10 Two Wire Detector Circuit OT 1 ON S G UIDE Class A Circuits Class A circuits also differentiate between short circuits across the loop and opens on the loop Supervision is accomplished by monitoring the level of current passing through the installation wiring and the end of line resistor which in a Class A circuit is an integral part of the fire alarm control panel Class A wiring must return to and be terminated in the control panel This technique requires a minimum of four conductors to be terminated at the panel and further requires that the fire alarm control panel is designed to monitor Class A circuits The additional cir cuitry necessary for Class A supervision enables the con trol panel to condition the initiating circuit to monitor the initiating circuit from both ends when in a trouble mode due to an open fault on the loop This conditioning ensures that all devices are capable of responding and reporting an alarm despite a single open or non simultane ous single ground fault on a circuit conductor The compatibility considerations of smoke detectors that were detailed in Class B circuits apply with Class A as well Figure 11 Wireless Circuits Wireless detectors and their internal transmitters derive their operating power from their internal battery or batter ies and are listed by Underwriters Laboratories Inc in accordance with requirements of NFPA 72 Supervision of the internal battery po
22. System Smoke Detectors SN SYSTEM S9 SENSOR APPLICATIONS GUIDE System Smoke Detectors Contents Foreword EE FR amaae tice attr tees Introduction EE TG Section 1 Standards that Apply 005 NERAICodesiand Standards m eee rn Buildingiand Fire Codes me en n nea E E E E restingikaboratorese IN Industry Rublicatons ss eee seem ace eee Manutaeturerskublicationserr PP Section 2 How Smoke Detectors Work lonization Smoke DetectonOperationt Photoelectric Smoke Detector Operation 0c eee ee eee ee Smoke Detector Design Consideration 20 00 c cece cece aes Section 4 Proper Detector Applications Placement and Spacing rrr errr rennin nar rrr rer 8 WheresloiPlace Detectorsin rer 8 Where NottoiPlace Detectors meen iirc celiac ms 9 SpeciallAppiicationDetectorse REESE REESE ER 10 Standardsfor SmokelDefec to rs a eee 10 DEtECTOTES P Gin GERE erick amen some ase nie meter Paras BE NED 10 Generalispacing Guidelines ae a 10 SpeciallSpacingiRroble mS er re 11 Detectors in Air Handling and Air Conditioning Systems 12 Detectors in Above Ceiling Plenum Areas Including Plenums UtilizediasiRartotthe AVAC System eter treet creer 12 Section 5 Testing Maintenance and Considerations in Selecting Detectors n essees sensar eenn Semice of Detectors omer eres cece A ce 13 Smoke Detectors Have Limitations eee sees ee ee ee T
23. ads be delayed until after drywall installation is completed or to protect detector heads from dust contamination If alarms occur whenever the heating system is turned on after an extended shutdown due to the accumulated dust burning off as the system components heat the detector system can be turned off for a short period while the heat ing system is activated and checked out or the start up of the heating system can be scheduled for an evening week end or other off hours period to minimize the effects of alarms on regular daytime activities Not all unwanted alarms are caused by dirt interference or other effects on the detectors If the control panel shows an alarm but no detectors in the zone are indicating an alarm condition the possibility of interference or a failure of a control panel component should also be investigated Responsibilities of Detector Owners and Installers The owners of smoke detector equipped fire alarm systems are responsible for maintaining the integrity of the detec tion system This can be accomplished by Maintaining an Alarm Log and training appropriate personnel to properly maintain the system as described above in the section titled What To Do When Unwanted Alarms Occur Maintaining a Detector Maintenance Log that records inspection testing and cleaning data for each detector in the system Refer to Section 6 of this manual Testing Maintenance and Service of Detectors for information on
24. alarm control unit shall be listed for use with the control unit Two wire Smoke Detector A smoke detector which initiates an alarm condition on the same two wires that also supply power to the detector Unwanted Alarm Any false alarm or nuisance alarm Wireless Smoke Detector A smoke detector which contains an internal battery or batteries that supply power to both the smoke detector and integral radio frequency transmitter The internal power source is supervised and degradation of the power source is communicated to the control panel On stimuli the detector transmits a radio signal to a repeater or Fire Alarm Control Unit FACU that in turn generates a signal or sta tus condition Appendix 2 Fire Alarm Log Customer Name S Y STEM S ENSOR Installation Date Installing Contractor Inspection and Test Date Inspection and Test Performed By Date Time Recorded By Check one Fire Trouble Location Bldg Zone Det Probable Cause Action Taken Action Taken By Name and Date gt N SYSTEM S92 SENSOR lt Makes Sense 800 736 7672 www systemsensor com 02002 System Sensor The company reserves the right to change specifications at any time A05 1003 002
25. alarm system installation wiring should be installed in compliance with Article 760 of NFPA 70 the National Electrical Code NEC the manufacturer s instructions and the requirements of the authority having jurisdiction Typical Wiring Techniques The primary rule of installation wiring is Follow the Manufacturer s Instructions This rule cannot be overemphasized The requirement for electrical supervision of the installation wires and their connections to initiating devices makes fire alarm system installation wiring very different than general wiring SYSTEM SEN A manufacturer s installation wiring drawing routes wires and shows connections in a certain manner to accommo date supervision requirements Any variance from the manufacturer s drawings might cause a portion of a circuit to be unsupervised and if an open or short circuit fault occurred it could prevent the circuit from being able to perform its intended function without giving the required trouble indication The rules of supervision are not very complex However unless an installer is experienced in fire alarm system instal lations he or she would not likely be familiar with them Smoke detector manufacturer s installation drawings will show how their detectors are to be connected into a system However a manufacturer s drawings may not show how devices located on the same floor but served by a different riser vertical wiring run should be connected The
26. alibrated or replaced Restore the zone or system at the completion of testing Notify all the persons contacted at the beginning of the test that testing has been completed and the system is again operational Some individuals rely on an aerosol chemical spray to test the sensitivity of a detector This can give unsatisfactory results since an aerosol chemical spray does not accurate ly test detector sensitivity NFPA 72 1999 Chapter 7 Section 7 3 2 1 notes that The detector sensitivity shall not be tested or measured using any device that adminis ters an unmeasured concentration of smoke or other aerosol into the detector The duration of spray distance between the detector and the aerosol container angle of discharge and different environmental conditions can pro duce random results In addition many aerosols leave an oily residue Over a period of time this oily residue can attract dust or dirt which can make a detector more sensi tive and result in nuisance alarms Be sure to follow the manufacturer s recommendation on test gas aerosol or smoke A P P L CAT 1 ON S G UIDE SYSTEM Section 6 i What to Do About Troubleshooting Unwanted Alarms Techniques No detection system is imper vious to unwanted alarms Statistically as the system size and the total number of detectors increases the total number of nuisance alarms per year tends to increase Historical experience in a given installation or data on
27. ally and cancel each other When combustion particles enter the sensing chamber its current decreases while the current of the reference chamber remains unchanged The resulting current imbalance is detected by the electronic circuitry See Figure 5 There are a number of conditions that can affect dual chamber ionization sensors dust excessive humidity condensation significant air currents and tiny insects can be misread as particles of combustion by the electronic circuitry monitoring the sensors HEE 0 O OO o Figure 1 Particle Radiation Pattern 3 oO A Figure 2 lon Distribution Figure 3 lon and Particles of Combustion Distribution Sensing Chamber Se Wi Source Reference Chamber Current Stable s Sensing Chamber Current Decreasing Reference Chamber Current Stable Figure 4 Dual Chamber Figure 5 Dual Chamber with Particles of Combustion A P P L CAT 1 ON S G UIDE SYSTEM Photoelectric Smoke Detector Operation Smoke produced by a fire affects the intensity of a light beam passing through air The smoke can block or obscure the beam It can also cause the light to scatter due to reflec tion off the smoke particles Photoelectric smoke detectors are designed to sense smoke by utilizing these effects of smoke on light Photoelectric Light Scat
28. are optimized for specific environments and should be considered Pinnacle Laser technology smoke detector is designed for use in areas that require extremely early warning of fire It is designed to detect the earliest particles of combustion making it ideal for clean rooms computer rooms or telecommunication centers any area where any damage is too much As Pinnacle is ultra sensitive to smoke as much as 100 times more sensitive than standard detectors care and judgement of application is needed to prevent unwanted alarms See System Sensor s Pinnacle Applications Guide For environments classified as hazardous System Sensor offers Intrinsically Safe Detectors designed to provide detection for high risk areas such as oil production facili ties refineries and chemical plants These units operate on low energy levels and are used with a safety barrier See our Guide for Proper Use of Intrinsically Safe Fire Protection Devices Standards for Smoke Detectors Underwriters Laboratories UL has three standards for smoke detectors one for duct detectors UL 268A one for single and multiple station smoke alarms UL 217 and one for systems type detectors UL 268 Detectors should only be used for the applications for which they are specifically listed The 2000 NFPA 101 Life Safety Code notes in Section 9 6 2 10 4 that single station smoke alarms shall sound an alarm only within an individual living unit suite of rooms
29. ating system is shut down When the system is operating the detector may be less responsive to a fire condition in the room below than will a detector located on the ceiling of the room below This may be due to blockage dilution and filtering of the air prior to its arrival at the detector location in the plenum area Since the air circulating through the plenums is usually at higher velocities than would be prevalent in the room below detector spacing should be reduced Also the dilution of the smoke in plenum spaces is an important consideration when utilizing smoke detectors rated for higher velocities Therefore plenum detectors should be utilized to detect fire in the plenum but should never be utilized as a substitute for duct detectors and open area detectors Maintenance requirements of detectors exposed to unusu al velocities above 300 fpm are generally increased due to the excessive dirt buildup and contamination present in these environments SYSTEM SENSOR Section 5 Smoke detectors are designed Testing to be as maintenance free as Maintenance possible However dust dirt and Service of and other foreign matter can late inside a detector s Detectors karen sensing elements and change its sensitivity They can become either more sensitive which may cause unwanted alarms or less sensitive which could reduce the amount of warning time given in case of a fire Both are undesirable Therefore detectors should
30. be tested periodically and maintained at regular intervals Follow closely the manu facturer s specific recommended practices for maintenance and testing Also refer to Appendix B of NFPA 90A and NFPA 72 Chapter 7 Caution Smoke detectors are sophisticated electronic devices that need periodic testing and maintenance To maintain the integrity of any fire alarm system it is important to have a qualified person periodically test the system Typical Inspection Test and Maintenance Practices Detectors should be given a visual inspection at installation and at least twice a year thereafter This ensures that each detector remains in good physical condition and that there are no changes that would affect detector performance such as building modifications occupancy hazards and environmental effects Notify the proper authorities that the smoke detector is undergoing maintenance and therefore the system will temporarily be out of service NOTE Disable the zone or system undergoing maintenance to prevent unwanted alarms and possible dispatch of the fire department Use a high power vacuum cleaner and remove dust from the detector by placing the nozzle as close as possible to the openings in the outside housing A nozzle with a brush attachment will assist in dust removal Some detector s sensing chambers can be removed for more thorough cleaning refer to the manufacturer s recommended proce dure for details Test each de
31. ber intended to reduce the occurrence of nui sance alarms Spot Point Detector A device whose detecting element is concentrated at a par ticular location Typical examples are bimetallic detectors fusible alloy detectors certain pneumatic rate of rise detec tors most smoke detectors and thermoelectric detectors Stratification An effect that occurs when air containing smoke particles or gaseous combustion products is heated by smoldering or burning material and becoming less dense than the sur rounding cooler air rises until it reaches a level at which there is no longer a difference in temperature between it and the surrounding air Stratification can also be caused by forced ventilation Trouble Supervision The ability of a fire alarm control unit FACU to detect a fault condition in the installation wiring which would pre vent normal operation of the fire alarm system Thermal Lag When a fixed temperature device operates the temperature of the surrounding air will always be higher than the oper ating temperature of the device itself This difference between the operating temperature of the device and the actual air temperature is commonly spoken of as thermal lag and is proportional to the rate at which the tempera ture is rising Two wire Compatibility Per NFPA 72 1999 edition All fire detection devices that receive their power from the initiating device circuit or use a signaling line circuit of a fire
32. cussion of detec tor placement in Section 4 Where To Place Detectors Burn characteristics and the value of assets being pro tected influence the spacing of detectors and the amount of protection provided in a specific room or area Refer to NFPA 72 1999 Section 2 3 6 for more detailed information on spacing of detectors under special applications Likewise if the contents are espe cially valuable for example sophisticated and expen sive machinery or irreplaceable records detectors should be placed closer together a ff 3 ft Minimum e Smoke Detectors at Ceiling o Smoke Detectors below Ceiling Figure 23 High Ceiling Area SMOKE DETECTORS Detectors in Air Handling and Air Conditioning Systems See NEMA Guide for Proper Use of Smoke Detectors in Duct Applications and NFPA 72 National Fire Alarm Code for more specific information Detectors in Above Ceiling Plenum Areas Including Plenums Utilized as Part of the HVAC System Detectors should be placed in plenum areas above ceiling air handling space in addition to the open area detectors installed in the open areas below and duct detectors installed in the ducts Plenum detectors are required to be listed or tested and approved for the air velocities within the environment in which they are to be installed Detectors placed in plenums MAY NOT be used as a sub stitute for open area protection because smoke may not be drawn into the plenum when the ventil
33. e owner s personnel These services can be provided by qualified outside organizations The installers of smoke detector equipped alarm systems are responsible for providing the owners with the neces sary information and training so that their personnel can maintain the integrity of the alarm system These respon sibilities should include e Providing copies of the specifications and installation instructions for the detectors control panel and auxil iary devices wiring diagrams and wire location infor mation and the manufacturer s recommendations for isolating the detection system wiring from other elec trical wiring to prevent interference and unwanted alarms e Verifying that the alarm system installation meets all applicable code requirements e Completely testing a newly installed expanded or modified alarm system to ensure that all components are working properly e Providing troubleshooting assistance to the owners for a specified break in period after installation in case problems develop SMOKE DETECTOR S S e Helping the owner set up appropriate Detector Maintenance and Alarm Logs for the system e Providing initial instruction and training to the owner s personnel or outside organization which will be monitoring and maintaining the system e Providing troubleshooting assistance if nuisance alarm problems cannot be solved satisfactorily by the owner s personnel or outside organization Where to Get H
34. elp if the Source of Unwanted Alarms Can t be Found In the event a series of unexplained unwanted alarms and or a review of the Alarm Log indicates that a problem situation exists the owner should conduct the initial inves tigation to find a solution If the owner s personnel are unable to determine the cause for the alarms the installer or representative of the manufacturer should be contacted to help pinpoint the problem Manufacturers can be contacted by phone for additional suggestions If factory assistance is needed a factory engi neer may be able to explain the source of the problem with data from your Alarm Log complete description of your alarm system including detector model numbers make and model number of the control panel and other components and a complete summary of all aspects of the problem that have already been checked SYSTEM SENSOR Appendix 1 Addressable System Smoke Glossary of Terms Detector System smoke detectors which in addition to providing alarm and trouble indica tions to a control unit are capable of communicating a unique identification address Air Sampling type Detector A sampling type detector consists of piping or tubing distri bution from the detector unit to the area s to be protected An air pump draws air from the protected area back to the detector through the air sampling ports and piping or tub ing At the detector the air is analyzed for fire particulate Alarm Signal
35. ensed rapidly by ceiling mount ed detectors Upward convection of smoke can be slowed or blocked by goods stored on the upper levels of the racks Multi level fire detection is required Detectors should be installed on the ceiling above each aisle and on intermediate levels of the racks adjacent to alternate pallet sections shown in NFPA 72 1999 A 2 3 6 5 A consultant s judgement may be required for specific installations Partitions Partitions and many types of large tall equipment standing on the floor can block the flow of smoke toward detectors Any partition or similar obstruction that is less than 18 inches 45 cm from the ceiling should be treated as a side wall dividing the area protected Air Stratification Air stratification in a room may keep air containing smoke from reaching ceiling mounted detectors Three conditions are known to accentuate air stratification when a layer of hot air exists under a poorly insulated roof heated by the sun cooler air will stratify the hot air layer at the ceiling when a layer of cold air exists under a poorly insulated roof cooled from the outside by cold air the heated air is cooled as it reaches the cold air layer or when a heating venti SENSOR Rectangles A 10 ft x 41 ft 410 sq ft B 15 ft x 39 ft 585 sa ft C 20 ft x 37 ft 740 sa ft D 25 ft x 34 ft 850 sa ft E 30 ft x 30 ft 900 sa ft Figure 20 Detector Coverage Patterns
36. ent regional organizations which write model building and fire codes which become law when adopted by local and state governments These codes specify smoke detector requirements based on building type and occupancy The organizations are Building Officials and Code Administrators BOCA 4051 West Flossmoor Road Country Club Hills Illinois 60478 5795 BOCA s National Building Code is generally used through out the northeast and midwest regions of the United States International Conference of Building Officials ICBO 5360 Workman Mill Road Whittier California 90601 2298 ICBO s Uniform Building Code is generally used through out the West and Southwest regions of the United States Southern Building Code Congress International SBCCI 900 Montclair Road Birmingham Alabama 35213 1206 SBCCI s Standard Building Code is generally used in the South and Southeast regions of the United States International Code Council Inc International Building Code International Fire Code 5360 Workman Mill Road Whittier California 90601 2298 The organizations listed above have formed an umbrella organization known as the International Code Council ICC for the purpose of combining the codes produced by the above three organizations into a single set of model building and fire codes ICC s International Building Code and International Fire Code were first published in 2000 and have been adopted by some states Testing Laboratories
37. ge of the detector its internal components may not function properly Manufacturers specifications should list acceptable temperatures in these ranges Areas with Combustion Particles Avoid areas where particles of combustion are nor mally present such as in kitchens or other areas with ovens and burners in garages where particles of com bustion are present in vehicle exhausts When a detec tor must be located in or adjacent to such an area a heat detector may be appropriate Manufacturing Areas Avoid manufacturing areas battery rooms or other areas where substantial quantities of vapors gases or fumes may be present Strong vapors can make detec tors overly sensitive or less sensitive than normal In very large concentrations gases heavier than air such as carbon dioxide may make detectors more sensitive while gases lighter than air such as helium may make them less sensitive Aerosol particles may collect on detector chamber surfaces and cause nuisance alarms Fluorescent Light Fixtures Avoid placement near fluorescent light fixtures Electrical noise generated by fluorescent light fixtures may cause unwanted alarms Install detectors at least 1 foot 0 3 m away from such light fixtures A P P L CAT 1 ON S G UIDE SYSTEM Special Application Detectors The guidelines in this document generally apply to stan dard open area smoke detectors System Sensor has a num ber of advanced technology detectors that
38. harged and some become negatively charged As these relatively large particles continue to combine with many other ions they become recombination centers and the total number of ionized particles in the chamber is reduced This reduction in the ionized particles results in a decrease in the chamber current that is sensed by elec tronic circuitry monitoring the chamber When the current is reduced by a predetermined amount a threshold is crossed and alarm condition is established Changes in humidity and atmospheric pressure affect the chamber current and create an effect similar to the effect of particles of combustion entering the sensing chamber To compensate for the possible effects of humidity and pressure changes the dual ionization chamber was developed and has become commonplace in the smoke detector market A dual chamber detector utilizes two ionization chambers one is a sensing chamber that is open to the outside air See Figure 4 The sensing chamber is affected by partic ulate matter humidity and atmospheric pressure The other is a reference chamber that is partially closed to out side air and affected only by humidity and atmospheric pressure because its tiny openings block the entry of larg er particulate matter including particles of combustion Electronic circuitry monitors both chambers and compares their outputs If the humidity or the atmospheric pressure changes both chambers outputs are affected equ
39. he minimum requirements of any local codes or ordinances Total coverage as defined in NFPA 72 is the definition of a complete fire detection system In some of the speci fied areas of coverage such as attics closets under open loading docks or platforms a heat detector may be more appropriate than a smoke detector Careful consideration should be given to the detector manufacturer s instructions and the following recommendations in this guide In general when only one detector is required in a room or space the detector should be placed as close to the center of the ceiling as possible Central location of the detector is best for sensing fires in any part of the room If a center location is not possible it may be placed no closer than 4 inches from the wall or if listed for wall mounting it may The guidelines in this section of the guide are adapted from Standards published by the National Fire Protection Association Quincy Massachusetts USA These standards include NFPA 72 National Fire Alarm Code NFPA 70 National Electrical Code Article 760 and NFPA 90A Installation of Air Conditioning and Ventilating Systems SYSTEM be mounted on the wall Wall mounted detectors should be located not less than 4 inches nor more than 12 inches from the ceiling to the top of the detector and at least 4 inches 10 cm from any corner wall junction See Figure 18 When air supply and or air return ducts are p
40. ing and air conditioning controls elevator call systems remote control equipment door closers etc and even the installation of microwave antenna If the alarm pattern supports the possibility of some kind of interference with a fairly definite initiation date all equip ment changes made in the building immediately prior to or concurrent with the beginning of the development of the alarm pattern should be reviewed In addition the wiring layouts of the alarm system and any recent building or sys tem modifications should be compared to make sure that the spacing and or shielding required to protect the alarm system wiring from other potentially interfering electrical systems was maintained Miscellaneous Causes of Unwanted Alarms Isolated alarm causes such as a maintenance person acci dentally triggering an alarm by touching a detector with a magnetic screwdriver can be ignored except to periodical ly remind maintenance personnel to be careful when work ing around detectors Steps should also be taken to protect detectors from dust whenever maintenance requires sawing sanding drilling or other dust producing operations in the vicinity of the detector heads to prevent false alarms due to the dust get ting into the detector sensing chambers In new construc tion applications drywall dust contamination affects all types of smoke detectors To help overcome this problem it is strongly recommended that installation of detector he
41. l the detector responds in a fire alarm condition Light Scattering The action of light being reflected and or refracted by smoke particles for detection by a photoelectric smoke detector The action of light being refracted or reflected Listed Equipment or materials included in a list published by an organization e g Underwriters Laboratories acceptable to the authority having jurisdiction and concerned with A P P L CAT 1 ON S G UIDE SYSTEM product evaluation that maintains periodic inspection of listed equipment or materials and whose listing states either that the equipment or material meets appropriate standards or has been tested and found suitable for use in a specified manner Note The means for identifying listed equipment may vary for each organization concerned with product evaluation some of which do not recognize equipment as listed unless it is also labeled Maintenance Condition Method of providing annunciation of a smoke detector that it is out of its listed sensitivity range National Fire Protection Association NFPA An organization that administers the development and publishing of codes standards and other materials con cerning all phases of fire safety Nuisance Alarm An unwanted alarm caused by smoke from cooking or cig arettes Obscuration A reduction in the atmospheric transparency caused by smoke usually expressed in percent per foot Particles of Combustion Substances
42. llation past detectors in other areas unrelated to the source of the contaminants Diagnosing problems of this kind requires that air move ments into the problem area especially near the ceiling be carefully checked and their sources be determined Experienced heating ventilating and air conditioning HVAC engineers or contractors usually have the training and specialized equipment flow meters etc to conduct such a study In very difficult cases a full scale smoke test may be required to solve the problem Conversely strong air streams near air inlet or supply ducts etc can also prevent a detector from signaling an alarm when a fire is present by blowing smoke away from the detector heads Inspect Detector for Dirt and Review Maintenance If the Alarm Log indicated that after several months or a year with a fairly stable alarm rate there is a gradual increase in the frequency of unwanted alarms this is usu ally an indication that the detectors in the system should be cleaned SYSTEM SENSOR NFPA standards require and smoke detector manufacturers recommend that all detectors be visually inspected twice a year Clean the detectors at least once a year or more frequent ly if environmental conditions warrant it See the section on Detector Testing and Maintenance in this guide for more details In cases where the probable cause of a number of alarms appears to be dust or dirt on the detectors detector main tenance sched
43. ly in this example detector spacing can exceed the given 30 foot spacing and still com ply with the code if any source of combustion is within 21 2 feet 6 4 meters of the horizontal projection of a detector and if no more than 900 square feet 82 8 square meters are being protected by one detector To determine what coverage patterns are permissible with in the 30 foot spacing start by tracing a circle with a radius of 21 2 feet Keeping in mind the fact that most rooms and areas to be protected are rectangular or square in shape any square or rectangle that fits within the circumference of the circle may be protected by one detector See Figure 20 30 ft 9 1 m 30 ft 9 1 m Figure 19 Typical Detector Spacing SYSTEM In other words if a diagonal through the center of the room is no greater than the diameter of the circle or 42 4 feet 12 8 meters one detector can be used under ideal condi tions Figure 21 shows how a length of hallway can be pro tected by only two detectors under ideal conditions Special Spacing Problems The ideal conditions upon which code guidelines are based do not exist in the majority of buildings Detector installers usually have to deal with a variety of problems such as uneven ceilings or ceilings crossed by beams and joists storage racks and partitions that obstruct the path of smoke toward detectors air stratification due to uninsulated roofs peaked or sloped ceilings
44. ng used should be contacted for any published information on their products Section 2 There are two basic types of How Smoke smoke detectors in use today Detectors Work ionization and photoelectric The sensing chambers of these detectors use different principles of operation to sense the visible or invisible particles of combustion given off in developing fires lonization Smoke Detector Operation A typical ionization chamber consists of two electrically charged plates and a radioactive source typically Americium 241 for ionizing the air between the plates See Figure 1 The radioactive source emits particles that collide with the air molecules and dislodge their electrons As molecules lose electrons they become positively charged ions As other molecules gain electrons they become negatively charged ions Equal numbers of positive and negative ions are created The positively charged ions are attracted to the negatively charged electrical plate while the negatively charged ions are attracted to the pos itively charged plate See Figure 2 This creates a small ionization current that can be measured by electronic cir cuitry connected to the plates normal condition in the detector Particles of combustion are much larger than the ionized air molecules As particles of combustion enter an ioniza tion chamber ionized air molecules collide and combine with them See Figure 3 Some particles become posi tively c
45. ntain an Alarm Log The next step for all alarms should be entry of a report into an Alarm Log A typical Alarm Log is shown in Appendix 2 page 19 Such a log serves immediate and long term purposes The Alarm Log indicates which individuals responded to the alarm and whether or not they took appropriate action Periodic review of the cumulative Alarm Log can help those responsible for the detection system discern patterns in the reported alarms Generally several months or even years of data may be necessary before patterns begin to emerge In a worst case example a pattern of repeated alarms or small fires in a particular area may indicate a serious defi ciency in safety practices that should be promptly correct ed In less obvious cases patterns are indicated by repeat ed alarms in the same or adjacent zones with similar prob able causes or repeated alarms in the same zone that occur at about the same time of day or time of year Effects of Location or Environment Check for the effects of location and environment Review the information in this guide Where To Place Detectors and Where NOT to Place Detectors to determine whether the detector s location or its environment is potentially causing the unwanted alarms Also refer to the installation manu al for further information One often overlooked source of problems is the placement of detectors where air streams carry smoke or chemical fumes from some areas of an insta
46. o Placement and wiring faults exist and that all Spacing parts of the system operate as intended A complete system checkout consists of testing each detector at its installed location and following the panel manufacturer s instruc tions for system checkout Also refer to NFPA 72 for addi tional information Where to Place Detectors Detector placement is critical to early warning functions To provide effective early warning of a developing fire sit uation smoke detectors should be installed in all areas of the protected premises Total coverage as defined by NFPA 72 should include all rooms halls storage areas base ments attics lofts and spaces above suspended ceilings including plenum areas utilized as part of the HVAC sys tem In addition this should include all closets elevator shafts enclosed stairways dumbwaiter shafts chutes and other subdivisions and accessible spaces Fire detection systems installed to meet local codes or ordi nances may not be adequate for early warning of fire Some codes or ordinances have minimum objectives such as capturing elevators or preventing circulation of smoke through the HVAC systems instead of early detection of fire A user should weigh the costs against the benefits of installing a complete fire detection system when any detec tion system is being installed The location quantity and zoning of detectors should be determined by what objec tives are desired rather than t
47. om interference from induced currents and noise in adjacent wiring systems radio frequency transmissions and other types of elec tromagnetic effects e Inadequate maintenance can result in the accumula tion of dust and dirt on the detector s sensing cham bers over a period of time Seasonal effects such as the reactivation of a building heating system after an extended summer shutdown can cause alarms e Building maintenance issues such as accidental trig gering of a detector s magnetic test switch or the introduction of plaster dust from drywall repairs into a detector s sensing chamber can cause unwanted alarms e Induced current effects from lightning storms can cause alarms e Infestation from insects small enough to enter the detector s sensing chamber e Vandalism or mischievous acts detectors set off as a prank have been found to be a problem in dormitories If an alarm occurs and a fire does not exist the alarm should be silenced the problem unit located and the alarm system controls reset so that the effectiveness of the detection system is restored SMOKE DETECTORS Make sure that all the detectors in the zone or pinpointed device s that show an alarm are checked before deciding that it is a false alarm If a fire does exist more than one detector may be in the alarm state although no signs of fire may be evident in the vicinity of the first activated detec tor The fire could be overlooked Mai
48. pen resulting in a trouble condition The required termination at the smoke detector may involve either screw terminals or wire pigtails Regardless of the method utilized removal of the smoke detector or a single installation wire must open the initiat ing circuit and result in a trouble signal at the control panel Screw termination of either side of the initiating circuit may require only one or two screws Figure 14 is an example of proper termination when one screw terminal is used Note that the installation conductor has been cut before termina tion This assures full supervision of the smoke detector Figure 15 details common connection errors In both exam ples removal of the smoke detector wire does not open the initiating circuit The fire alarm control panel will not rec ognize a trouble condition and the detector that has been deliberately or inadvertently disconnected will be disabled Smoke Detector A ak S O R Smoke Detector Smoke Detector Figure 12 Incorrect Wiring Method Smoke Detector Smoke Detector Smoke Detector Figure 13 Correct Wiring Method i NAG Figure 14 Proper Termination 2 Z Figure 15 Improper Termination A PPLICAT FEE Wire Nut 1 ON S G UIDE SYSTEM Figure 16 is an example of properly connected smoke detectors provided with pigtails This method of
49. resent in a room or space the detector s should not be placed in the path of the air flow supply or return duct NFPA 72 1999 Edition Smoke tests are helpful in determining proper placement Special attention should be given to smoke travel directions and velocity since either can affect detector performance Placement of detectors near air conditioning or incoming air vents can also cause excessive accumulation of dust and dirt on the detectors This dirt can cause detectors to malfunction and cause unwanted alarms Detectors should not be located closer than 3 feet from an air supply diffuser or an air return vent Spot type detectors in properly engineered systems may also be placed in return air ducts or in approved duct detector housings designed for this application Although duct detectors are not a substitute for open area detectors they can provide an effective method of initiating building control functions to prevent smoke from being transported from the fire area to other parts of a building See Duct Smoke Detector Applications Guide SENSOR 4 in 10 cm Ceiling Never Here Acceptable Here Top of Detector Acceptable Here Note Measurements shown are to the closest edge of the detector Figure 18 Wall Mounted Detector Placement 4 in 10 cm Minimum Side Wall 12 in 30 cm Maximum Where Not To Place Detectors See Table A 2 3 6 1 2A in NFPA 72 1999 One of the major cause
50. s of unwanted alarms is improper placement of detectors The best way to avoid unwanted alarms is not to install detectors in environments that can cause them to malfunction or to install detectors specially designed for those environments Examples follow Excessively Dusty or Dirty Areas In excessively dusty or dirty areas consider using the Filtrex smoke detector This detector incorporates a microprocessor controlled air intake fan and filter that allows the unit to be installed in areas where ordinary detectors cannot be used Filtrex is an intelligent smoke detector that removes airborne particles before they reach the sensing chamber It is ideal for textile mills dusty manufacturing facilities paper mills and recycling centers For more information see System Sensor s Filtrex Applications Guide Outdoors Avoid using detectors outdoors in open storage sheds or other open structures affected by dust air currents or excessive humidity and temperature extremes Wet or Excessively Humid Areas Avoid damp wet or excessively humid areas or next to bathrooms with showers Elevator Lobbies Do not place over ashtrays or where people will smoke while waiting for the elevator Extreme Cold or Hot Environments Avoid very cold or very hot environments or unheat ed buildings or rooms where the temperature can fall below or exceed the operating temperature range of the detector At temperatures above or below the oper ating ran
51. similar sized buildings with similar utilization patterns can provide a basis for a rough indica tion of how many nuisance alarms are probable during a 12 month span however no two installations are identical In small to moderate sized detection systems protecting relatively combustion free environments like office build ings more than one or two unwanted alarms per year would be unusual In more adverse environments such as laboratory or manufacturing facilities where combustion processes are present more frequent alarms can be antici pated In very adverse environments one alarm per month might not be considered excessive After the first few months which serve as a shakedown period it should be possible to arrive at some reasonable expectation for probable unwanted alarms from the sys tem After that any unexpected change in frequency or dis tribution indicates a problem that should be investigated The best way to monitor alarm frequency and distribution is to maintain an alarm log Reasons for Unwanted Alarms Unwanted alarms can result from a wide variety of causes including e Improper locations are environments where they will not operate properly because of temperature extremes excessive dust dirt or humidity excessive air flow rates or the normal presence of combustion particles in the air streams surrounding the detectors e Improper installation can occur when detectors and their wiring are not protected fr
52. tector s sensitivity per the manufacturer s rec ommended procedure within one year after installation and every alternate year thereafter Test each detector functionally in place annually as detailed in NFPA 72 1999 Chapter 7 If a detector s sensitivity is within specifications nothing further needs to be done to the detector If the detector s sensitivity is outside specifications clean the detector and retest If that does not place the sensitivity within the unit specified range then follow the manufacturer s recom mended procedure Restore zone or system at the completion of testing Notify the proper authorities that testing has been com pleted and the system is again operational Refer to paragraph 7 4 1 of NFPA 72 for additional infor mation To assure that each smoke detector is within its listed and marked sensitivity range it should be tested using either A calibrated test method or e The manufacturer s calibrated sensitivity test instru ment or Listed control equipment arranged for the purpose or Other calibrated sensitivity test method acceptable to the authority having jurisdiction Detectors found to have a sensitivity of 0 25 percent ft obscuration or more outside the listed and marked sensi tivity range should be cleaned and recalibrated or replaced Exception Detectors listed as field adjustable may be either adjusted within the listed and marked sensitivity range cleaned and rec
53. tering Smoke Detector Most photoelectric smoke detectors are of the spot type and operate on the light scattering principle A light emitting diode LED is beamed into an area not normally seen by a photosensitive element generally a photodiode See Figure 6 When smoke particles enter the light path light strikes the particles Figure 7 and is reflected onto the pho tosensitive device causing the detector to respond JE W SMOKE DETECTORS Photoelectric Light Obscuration Smoke Detector Another type of photoelectric detector the light obscura tion detector employs a light source and a photosensitive receiving device such as a photodiode see Figure 8 When smoke particles partially block the light beam Figure 9 the reduction in light reaching the photosensi tive device alters its output The change in output is sensed by the detector s circuitry and when the threshold is crossed an alarm is initiated Obscuration type detectors are usually of the projected beam type where the light source spans the area to be protected Q Light Source Light Sensitive Device Figure 6 Light Scattering Detector Light Source Light Sensitive Device Light Source Light Sensitive Device Figure 7 Light Scattering Detector with Smoke Light Source Light Sensitive Device M Figure 8 Light Obscuration Detector
54. tiating device cir cuit can supply This could result in the inability of the relay to control auxiliary equipment to which it is con nected e When using wireless detectors follow the manufactur er s installation instructions to assure proper radio communication between the smoke detector and the control panel e Observe polarity when required e Protect detectors against contamination during con struction or renovation e Carefully follow the manufacturer s instructions installation Don t e T tap smoke detectors or circuit conductors except when specifically permitted by the manufacturer as part of an intelligent addressable system e Loop uncut installation conductors around screw ter minations e Exceed the maximum resistance permitted for the ini tiating device system e Exceed the number of 2 wire detectors allowed on a 2 wire initiating circuit specified by UL Wiring and System Checkout As required for all installation wiring of fire alarm systems check the detector loop wiring for grounds short circuits and open faults before the system is placed into operation Each detector should be tested in accordance with the manufacturer s instructions When using wireless detectors verify the radio signal trans mission strength in accordance with the installation manual Section 4 After all detectors have been Proper Detector installed test the complete Applications system to ensure that n
55. ual fire alarm stations in the hallways and common areas of the complex and resi dential single station type smoke detectors and heat detec tors in the individual apartments The system detectors manual stations and heat detectors would be connected to a control panel sound a general alarm and automatically notify the proper authorities that a fire condition exists The residential smoke detectors located in the apartments would be interconnected only within the individual living quarters of each apartment These residential units would sound an alarm only in the apartment where a fire started Detector Spacing General Spacing Guidelines Some fire protection codes specify detector spacing on a given center to center distance between detectors under ideal conditions These distances are based on rooms with smooth ceilings with no physical obstructions between the contents being protected and the detectors Moreover they are also based on a maximum ceiling height and on the assumption that the value and the combustible nature of the contents of the room to be protected do not warrant greater protection or closer spacing If we assume a typical center distance spacing guideline is 30 feet 90 meters how do we determine whether a given room or space can be protected by a single detector Figure 19 shows four detectors spaced horizontally and vertically 30 feet 9 meters apart Detectors B and D however are more than 30 feet apart Clear
56. ules should be reviewed to determine the dates when the detectors were last cleaned and tested If the detectors are due or overdue for maintenance schedul ing and performing the recommended cleaning and testing should eliminate the problem If the problem resulted from a temporary overall increase in airborne dust due to nearby construction scheduling a one time special cleaning for all the detectors in the system should alleviate the problem If the problem is confined to one or two zones and is the result of higher dust levels in a particular area scheduling the detectors in those areas for more frequent maintenance and cleaning may prevent the development of similar alarm problems in the future Effects of Other Systems on Alarm System In checking for the effects of other systems on the alarm system wiring the Alarm Log may be very valuable in help ing to pinpoint relationships among apparently causeless alarms One important fact that can be obtained from an Alarm Log is the beginning date for a rash of apparently causeless alarms that may or may not be grouped around one particular zone The sudden onset of such a group of alarms may result when an addition or change in the alarm system or in another electrical or electromechanical system in the building affects the detectors or the alarm system circuitry Systems that can affect the alarm system include other security systems walkie talkie mobile telephones heat ing ventilat
57. wer source is incorporated within the smoke detector circuitry If the battery power source depletes to the threshold specified by Underwriters Laboratories the smoke detector will sound a local alert and initiate a trouble signal once each hour for a minimum of seven days or until the battery or batteries are replaced The wireless initiating devices are supervised for tamper and or removal by initiating a distinct trouble signal Each wireless device also initiates a test transmission every hour to verify the reliability of the communication circuit Any device failing to communicate is identified on the control panel no less than every four hours General Zoning Guidelines The faster the source of an alarm can be pinpointed the faster action can be taken Although formal rules for zon ing are not given in fire protection codes except for wire less devices where each smoke detector must be individu ally identified it is always sensible to zone any system that contains more than a small number of detectors Experienced detector installers and system designers rec ommend the following e Establish at least one zone on every protected floor e Zone natural subdivisions of a large building such as separate wings on a single floor Minimize the number of detectors in each zone Fewer detectors on a zone will speed up locating the fire and simplify troubleshooting e Install duct detectors in different zones than open area detectors
58. ypical Inspection Test and Maintenance Practices 13 Secuond SilypicalSystemk yout ee eae qeeeec seer Section 6 Troubleshooting Techniques 14 EleoinicaliSupenvisioneere s ERE LEES SKER EDER SKA SKEER ER EESERE What to Do About Unwante dfAlarm seerne 14 Class B Circuits ever eee eee eee Reasons for UnwantedJAlarm Seeee eee eee seer ete ENE 14 GlassAlCreuts as Maintainenfalanmilo o PE 14 NYTE JESSIE GUTT PEER Effects of Location or Environment 0 0eeeeeeevee esas 14 General Zoning GUGEMIGS 0002202000072 senncvssasenavueccsnevexe Inspect Detector for Dirt and Review Maintenance 14 fire Sate MEMOS PE Effects of other Systems on Alarm System Wiring 00 15 Smoke Detector Installation uvenner nunne Miscellaneous Causes of Unwanted Alarms 0eeee seca ee 15 WiringiInstallation Guidehngs a anneanne Responsibilities of Detector Owners and Installers 15 Typical Wiring Techniques 0 cee ee eee ees Where to Get Help if the Source of Unwanted Alarms Can t be Found 16 Wireless Systems 8 Need em B Appendix 1 Glossary oriens eee eee 17 Miringlandks ystemiC He CK OLE ae ent nnn anes ree Appendix 2 Alarmi LOG oncaccccpaancconaagoccnaencapas 19 Foreword Studies have shown that in the United States the use of early warning fire and smoke detection systems has resulted in a significant reduction overall in

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