System Sensor Reducing Detector-based Nuisance Alarms

March 2007 Paper Solving Detector based Nuisance Alarms Confusion Reducing Detector based Nuisance Alarms Detector based Nuisance Alarms alarms represent one of the most significant problems facing the fire alarm industry today Each year nuisance result in countless service calls and fire department dispatches not to mention millions of dollars in fines Left nuisance alarms can become life threatening for a building occupants as they may become confused between alarms and true emergency situations manufacturers industry associations and alarm companies alike have set out to combat this problem through training and a variety of new product developments System Sensor has joined the effort through innovative detection techniques and capabilities represented most recently by the introduction of the new i3 series smoke order for you to gain a broader perspective on nuisance alarms this paper provides a brief overview of their impact causes and some of the ways in which they can be mitigated Alarms The Facts alarms are not the same as false alarms However since nuisance alarms and false alarms both generate an signal the two terms are often misapplied A nuisance alarm is caused by conditions resembling smoke but are not by sources of fire Examples include dust and steam Conversely a false alarm is the result of conditions that do resemble smoke whatsoever including defective products vandalism etc following are just a few of the statistics that illustrate the relationship that exists between fire alarm systems smoke and nuisance alarms 2000 United States fire departments responded to 2,126,500 unwarranted alarms a 4.3 increase over 1999 and 51 increase over 1988.1 alarms that were estimated to result from some form of system malfunction accounted for 884,000 or of these alarms a 1.9 decrease over 1999 but a 61 increase over 1988.2 a recent survey fire chiefs estimated that one false alarm occurs per 100 detectors in use each year study of Veterans Administration hospitals found 15.8 unwanted activations for every real alarm or one unwanted for every six devices per year 4 costly are nuisance alarms One study indicated that the Fire Department is paid 150 for each avoidable or nuisance call 5 Though such costs can be easily quantified nuisance alarms also result in significant behavioral costs such as during an alarm condition nuisance conditions often translate to a lower confidence in the fire alarm system Case in point In a survey for the National Fire Protection Association NFPA only 7 of the respondents who reported an alarm thought was a fire and that they should evacuate the premises 6 Given an actual emergency situation results like these could tragic the Causes what exactly causes nuisance alarms in smoke detectors Nuisance alarms occur when detectors come in contact with sources of smoke steam moisture or humidity In fact one third of the devices studied for nuisance alarms in National Smoke Detector Project found that they were located in areas near often less than five feet a potential source smoke steam or moisture sufficient to produce nuisance alarms 7 dust or accumulations of dust and dirt can also cause nuisance alarms if the detector is not cleaned on a regular as recommended by NFPA 72 Inspection Testing and Maintenance guidelines Without the proper maintenance time the smoke detector may become more sensitive which could eventually lead to a nuisance alarm other studies cite smoke detectors featuring constant threshold sensitivity as a contributor to nuisance alarms 8 In words these detectors may not effectively discriminate between fire and non fire sources of smoke This restriction have contributed to the 95 frequency of unwanted alarms reported by smoke detectors in the 1980 according to Fire Journal 9 Sensor Advanced Ideas Advanced Solutions Confusion Reducing Detector based Nuisance Alarms Nuisance Alarms a number of industry associations as well as the manufacturing community are taking steps to reduce likelihood of nuisance alarms Organizations like the NFPA and the Automatic Fire Alarm Association AFAA are to promoting greater awareness and proper fire alarm installation requirements and practices Also NICET offers a means to verify that a fire professional has met the appropriate educational requirements to install or a fire alarm system a manufacturing perspective fire alarm suppliers continue to develop and introduce new technologies intended assure greater performance and avoid unnecessary nuisance alarms As it relates specifically to smoke detectors two being attacked include short duration effects such as airborne particles within the detector chamber and longer factors like settled dust accumulations To address these concerns manufacturers have begun to incorporate smart within the detector microprocessors Arguably the two most noteworthy are smoothing algorithms and drift Algorithms For Short Duration Effects smoke detectors measure the condition of the detector chamber on a pre determined periodic basis specifically for smoke As smoke enters a detector the chamber measurement will begin to increase toward the detector fixed threshold If enough measurements exceed the detector alarm threshold an alarm is then initiated 1 2 non smoke effects may mistakenly a surge or in the detector measurements These spikes may caused by a number of factors including dust particles disturbances of settled within the chamber RF interference insects etc As is the case with smoke if enough measurements exceed the alarm threshold an alarm is then In this case however a nuisance is generated refer to Figures 1 and 2 algorithms combat these effects a series of complex decision matrices screen out the effects of short duration and spikes in the detector chamber These algorithms throw out measurements refer to Figures 3 4 hence avoiding a nuisance alarm 3 4 Compensation For Long Term Effects airborne particles accumulated dust presents a longer term concern for smoke detectors Over time dust and dirt to build up within the detector chamber As this build up occurs the smoke detector becomes more sensitive refer Figure 5 Ultimately the detector may become so dirty that its sensitivity exceeds its alarm threshold hereby generating nuisance alarm compensation automatically adjusts the sensitivity of the smoke detector as it becomes dusty or dirty refer to 6 However the detector performance in measuring and responding to smoke remains unaffected The result is reduced chance of nuisance alarms without sacrificing detector performance 5 drift compensation and smoothing algorithms have been available for years However these features have historically reserved for analog detectors continued development capabilities are more readily available in detector designs with System Sensor new i3 of smoke detectors they are powerful than ever 6 Sensor Advanced Ideas Advanced Solutions Confusion Reducing Detector based Nuisance Alarms Series Detectors An Effective Solution new i3 series detectors from System Sensor represent the next wave in conventional smoke detection Though the i3 refers to Installation ease Intelligence and Instant inspection it is the line intelligent capabilities that help reduce alarms conventional smoke detectors have not featured drift compensation Today only a limited few offer drift while fewer still offer smoothing algorithms The i3 detectors however are equipped with both capabilities address both the short duration and long term causes of nuisance alarms System Sensor didn stop there as the i3 series drift compensation is arguably the most robust in the industry today the i3 detector sensitivity changes it continues to compensate for a longer period of time In fact the i3 series drift is capable of compensating as much as fifteen times the amount of dust dirt that other detectors equipped drift compensation can handle The net result is the assurance that the i3 series will generate fewer nuisance alarms reduce unnecessary service calls