System Sensor LED vs Xenon

White Paper 2014 Viewing Performance of Visual Notification Technologies of light output in ANSI UL 1971 Standard for Signaling Devices for the Hearing performance standard for emergency visual signaling appliances has long been based a calculation called effective intensity an estimate of the intensity of a flashing light versus a light estimate has worked well to predict viewing effectiveness as long as the emergency appliances tested such as the predominant xenon strobe technology have similar pulse durations that produce similar peak intensities i a recent review of research and follow up human behavior laboratory study provided the Fire Protection Research Foundation FPRF of the National Fire Protection Association finds that other light sources such as LEDs that use a longer pulse duration to achieve same effective intensities as xenon strobes are not detected as reliably when viewed indirectly a reflection on room surfaces iii white paper summarizes some key findings of this study and provides recommendations for visual emergency notification devices based on these results viii Challenges with all life safety systems designers and installers of emergency notification systems are first concerned with never compromising safety of the individuals that their systems protect In practice this requires fire and emergency system professionals to use experience and knowledge to design and install systems that meet the unique requirements and challenges of each individual It also requires choosing notification devices that meet both application requirements and UL and NFPA 72 standards must accomplish both of these goals while staying within budget and managing system costs One way to do this is by devices for the system that require the least amount of current draw This enables the designer to lay out a system that can more devices on each fire alarm control panel FACP notification appliance circuit NAC which potentially translates into panels power sources and lower costs for the overall system visual signaling devices light emitting diode LED technology has recently entered the market The LED strobes available today to meet minimum NFPA and UL standards while in some limited applications depending on candela setting providing power efficiency over the predominant xenon strobe technology intensity an estimate of the luminous intensity of a flashing light that has equivalent visual effectiveness as a steady burning is a calculation that has served as the test criteria for the current NFPA 72 and ANSI UL 1971 performance standard for visual appliances LED strobe technology on the market meets the current performance standard in order to do so the pulse duration of these must be increased over the time required for the predominant xenon strobe technology This increase in pulse duration while these newer technologies to meet the performance standard may result in lower real world detection performance versus strobe technology thus limiting the predictive power of the current performance standard Sensor Advanced Ideas Advanced Solutions Indirect Viewing Performance of Visual Emergency Notification Technologiesfirealarmresources com a recent review of research performed by the RPI Lighting Research Center on behalf of NFPA Fire Protection Research Foundation intensity may not be predictive of visual detection of signal lights when these are viewed indirectly reflected on surfaces v a result the Fire Protection Research Foundation commissioned a human factors laboratory study to test the viewing performance different lighting technologies including commercially available emergency notification visual signals What this study shows is that intensity not a useful predictive metric for the performance of visual signals having different durations v result begs the question meeting the current performance standard duration with LED technologies protect the public as as the predominant xenon strobe technologies remainder of this white paper will summarize the methods of the human factors research study as it relates to emergency notification provide an overview of some of the key results and provide our recommendations based on those results Viewing Study Setup vi subjects for the human factors study were seated at a table in a large rectangular classroom facing a white painted wall White walls were also on either side of the subject The test light source was mounted from the ceiling about one foot away from the behind the test subject experiments had subjects look directly at the wall in front of them In other experiments the subjects were asked to perform verification tasks NVTs on the table in front of them in order to test how well they detected the flashing light with their vision study included 7 total experiments with 10 subjects in each experiment Two experiments 4 and 5 used a commercially available notification visual signal xenon strobe set to the nominal 15 cd setting and standard pulse duration along with LED light In each of these experiments light sources were flashed at different intensities and rates The ambient illuminance was also varied were exposed to each experimental condition flashing light at different rates and intensities in a random order for 10 seconds They were then asked to report if they detected the flashing light They were also asked to rate the ease of detection and level of urgency of each signal if detected interest for indirect viewing performance experiment 4 had subjects performing the NVT The results of experiment 4 are summarized the following section for Experiments 4 experiment 4 subjects were asked to perform the NVT a number task on the table in front of them in order to test peripheral of light sources Sensor Advanced Ideas Advanced Solutions Indirect Viewing Performance of Visual Emergency Notification Technologiesfirealarmresources com Performance 4 500 lx 1 Hz visual task ms ms ms ms Intensity cd detection of LED light sources as shown in the table in this experiment was lower However the xenon strobe light source detected 100 percent of the time In fact the highest performing LED light source pulse durations 100 ms and 25 ms were only 70 percent of the time even at higher effective intensities than the xenon strobe LED sources similarly underperformed the xenon strobe technology in ease of detection and urgency of the signal see the full for complete results on the NFPA research report report notification appliances using a longer pulse duration might not alert individuals as effectively xenon based products UL has created a Task Group to work on updating the standard to address the performance differences the future using new light sources capable of a shorter pulse duration and complying with the new as yet undefined standard will new notification appliances with alternate light sources such as LEDs a viable option Until then the research has demonstrated xenon bulbs are the best technology to use for alerting people Bullough JD Skinner NP Zhu Y 2013 Parameters for Indirect Viewing of Visual Signals Used in Emergency Notification Quincy MA Fire Protection Research Foundation p 1 Ibid Ibid Ibid Ibid p iii Ibid p 16 For the complete human factors study methodology view the complete report at nfpa org media Files Research Research 20Foundation Research 20Foundation 20reports more information please contact Sensor Ohio Avenue Charles Illinois 60174 1 800 sensor2 System Sensor Product specifications subject to change without notice 5 14 Indirect Viewing Performance of Visual Emergency Notification Technologiesfirealarmresources com