Evaluation of the NFPA 72 Spacing Requirements for Waffle Ceilings

Evaluation of the NFPA 72 Spacing Requirements for Waffle Ceilings Stephen M. Olenick 1, Richard J. Roby, Douglas J. Carpenter, and Adam Goodman Combustion Science & Engineering, Inc. 8940 Old Annapolis Road, Suite L Columbia, Maryland 21045 (410) 884-3266 Abstract The National Fire Alarm Code (NFPA 72), 2007 edition, is the authoritative document on smoke detector placement in the United States. Referenced in the model building codes and adopted in most jurisdictions at the local, state, and federal levels, it lays the groundwork for safe placement of smoke detectors for optimum fire safety. Based upon research conducted for the National Fire Protection Research Foundation, the spacing of smoke detectors for waffle ceilings was changed in the 2007 edition of the code. Depending upon the height of the ceiling, depth of the beams forming the waffle pattern, and size of the pockets, certain configurations allow the designer to space smoke detectors as if the ceiling were smooth instead of previous versions of the code that required a smoke detector in each pocket. The rational for the change was the results of the Research Foundation funded project that determined that a reservoir effect was causing the pockets to be beneficial to earlier smoke detector activation. Peer-review of this Research Foundation work, utilizing the new smoke detector activation algorithm present in Fire Dynamics Simulator (FDS version 5.0.0), indicates that the code change as written may be resulting in delayed activation of the smoke detectors. A specific example of a 2007 NFPA 72 code compliant design was analyzed utilizing FDS to demonstrate the difference in activation times of real smoke detectors on waffle ceilings. This example shows that smoke detector activation time is substantially delayed under some waffle ceiling scenarios if the smooth ceiling spacing is used. Background A recent change in detector spacing for beamed and waffle-type ceilings was approved in the 2007 edition of NFPA 72: National Fire Alarm Code. This new code eliminates the requirement that a smoke detector be placed in every beam pocket and waffle indentation for many textured ceilings. The revisions to the code allow smooth ceiling detector spacing to be used when the beams are less than 2 deep and no greater than 12 spacing in both directions. This change in the code was justified on the notion that a large beamed-ceiling room would be required to have an inordinate number of smoke detectors if a detector was required in every pocket. The technical justification for this change in the smoke detector spacing requirements in corridors and on beamed and waffle-type ceilings was provided by Computational Fluid Dynamics (CFD) modeling performer as part of a NFPA Research Foundation project [10]. As a result of the CFD modeling, it was determined that for ceiling pockets created by certain sized beams of a given spacing and depth, the smoke detector spacing for flat ceilings can be used, as 1 Corresponding author: solenick@csefire.com

opposed to the requirement of a detector in every pocket, with no significant reduction in safety. Summary of Seminal Work In order to justify the change in the code, Fire Dynamics Simulator (FDS) was used to run a series of computer models of fires in corridors and waffle ceiling rooms. However, the analysis presented here only examines the work on waffle ceilings. Computer simulations were run with ceiling heights of 12, 18 and 24 and used beam depths of 1 and 2. The beams were spaced at 3, 6, and 12 intervals, on center. Smoke detectors or monitoring stations were placed in the center of each pocket in the model, as was previously required in NFPA 72 (2002). Sensing stations were also placed on the ceiling and on the underside of the beams at the spacing currently approved under NFPA 72 (2007) for smooth ceilings. The 2007 requirement is that detectors must be spaced at 30 intervals, detector to detector. Therefore, in a worst-case scenario, a detector could be 15 in both the x and y directions from the centerline of a fire, resulting in a total maximum distance from the fire to the detector of approximately 21. A view of the model geometry used for a 12 ceiling simulation with beams at 12 on center and 2 deep from the ceiling is shown in Figure 1. A C B Figure 1. 12 ceiling, 2 beam depth, 12 beam spacing geometry. As can be seen from Figure 1, Detector A represents the location required by the previous edition of NFPA 72 (2002), where the nearest detector to the fire would be on the ceiling at the center of the first beam pocket. Since this detector is closest to the fire,

presumably this detector would alarm first to the fire. According to the new changes to the code in NFPA 72 (2007 edition), a detector spaced according to smooth ceiling spacing could be located sufficiently far from the fire to be in the second beam pocket, shown as Detector B in Figure 1. A detector on the bottom of the first beam (Detector C) could also satisfy the new requirements. However, the Detector B location is the worstcase scenario, because it is farthest from the fire and is located behind the barrier created by the beamed ceiling. For comparison, a model was also run with the same inputs, but with a smooth ceiling configuration (i.e., the beams no longer present). It should be noted that the second pocket, where detector B was located, was only modeled as a partial pocket in the previous analysis in some of the scenarios depending on the spacing of the pockets. As can be seen in Figure 1, the partial second beam pocket extends to the edges of the computational domain and therefore is open on two of the four sides, allowing smoke to simply exit the domain with no buildup. In the previous work, the Geiman and Gottuk optical density thresholds [4] were used as the primary means to determine when the smoke detectors activated. A secondary means of determining time to detector activation, a critical velocity along with a temperature correlation as surrogate conditions to confirm activation, was also used. The critical velocity used was 0.13 m/s +- 0.07 m/s, and the temperature correlation used was a 4 C temperature rise for ionization detectors and a 13 C temperature rise for photoelectric detectors. In the initial analysis, it was established that a 60 second difference between activation of the detectors with beams present when compared to a smooth ceiling as the threshold of a significant activation time difference. No justification for the use of a 60 second threshold was provided in the report. The initial work examined smoke detector activation times for both a beamed and a smooth ceiling, based on the maximum spacing of detectors allowed for a smooth ceiling configuration (21 ). According to the report, the detector activation times for the case with beams and the case without beams were within 60 seconds of each other. Based on this activation time difference of less than 60 seconds, it was concluded that the presence of ceiling beams made no significant difference in detector activation time. However, as reported in the report, the detector placed in the second beam pocket according to the smooth ceiling spacing for a 12 on center beam spacing and 2 deep beams (Detector B) never reached the alarm threshold. The report explained the failure of the detector to alarm by the lack of a reservoir effect. According to the report, the reservoir effect occurs when a beam pocket causes the smoke to accumulate within that pocket before spilling over into the next pocket. As can be seen in Figure 1, if the smooth ceiling spacing is used, the detector nearest to the fire becomes Detector B, which is in the second beam pocket. Since in the model for this scenario the second pocket was only a partial pocket, smoke flowed out of the domain instead of accumulating as it would if the pocket were complete on all sides. According to the initial report, the detector in this pocket, Detector B, failed to alarm because the model domain was not extended sufficiently to create a completely enclosed pocket around Detector B, not because the smooth ceiling detector spacing was inappropriate. Based on the modeling, it was determined that the ceiling beams will not significantly impact the time to smoke detector activation if the flat ceiling detector spacing is used. The work was presented to the NFPA 72 committee responsible for this section of the code dealing with the placement of smoke detectors, and the work was

accepted, resulting in the change in NFPA 72, 2007 edition. The reasoning for the change in the code is that while the beams may block some of the ceiling jet, the pockets will allow for greater temperature rise and buildup of smoke, and create greater smoke velocity due to the smoke spilling out of each pocket into adjacent pockets. The trapping of smoke and heat in the pockets was termed the reservoir effect. Comparison Models In order to evaluate the present day accuracy and reproducibility of the initial work, the authors of this paper performed a series of FDS modeling runs using the new, validated, Smoke Detector Activation Algorithm (SDAA), as well as the Geiman and Gottuk and temperature correlations. The ultimate goal of this work was to determine independently, based on modeling and analysis, whether the conclusions of the initial work are justified. For this analysis, a geometry where the ceiling was 12 high and the beams were 1 or 2 deep and spaced 12 on center was used. According to the new changes in NFPA 72, these geometries would qualify for smooth ceiling spacing of smoke detectors. Smoke detectors were included in the first beam pocket (Detector A) according to the previous NFPA 72 requirements, and then included in the second beam pocket according to smooth ceiling spacing (Detector B) allowed under the current NFPA 72 code. Smoke detectors utilizing realistic lag time coefficients, termed Cleary I1, Cleary I2, and Heskestad L=1.8m detectors, were implemented in this model because they represent real detectors that would be expected to be found installed in buildings, based on testing done by Cleary [3] and by Heskestad [6]. Two different heat release rates were examined: a fixed 100 kw heat release rate and a variable heat release rate based on a medium t-squared fire. According to the initial report, this 100 kw fire should be detectable for a 12 ceiling, with or without beams. In both cases, the fuel was Methyl Methacrylate (MMA), a fuel that has a relatively large soot yield of 0.022 kg/kg fuel as defined in the FDS material database, when compared to other ordinary combustibles such as wood, paper, or cloth. This high soot yield will lead to earlier detector activations than would be observed with other ordinary combustibles. Therefore, the use of this high soot yield fuel will tend to reduce the time to detector activations in both the smooth and beamed ceiling cases. In order to test the observation in the initial report that the partial pocket was responsible for the detector failing to alarm in the second pocket (Detector B) for this particular scenario, for the current simulations, the domain was extended to ensure that this pocket was fully enclosed, allowing for the so-called reservoir effect to occur. A depiction of the extended domain as used in this modeling is shown as Figure 2.

A C B Figure 2. 12 ceiling, 2 beam depth, 12 beam spacing geometry. Note that the furthest pocket is surrounded on all sides, allowing buildup and the reservoir effect. For this analysis, simulations were run with the 12 ceiling and 12 beam spacing. Two different iterations were performed, one with the beams 2 deep, and the other with the beams 1 deep. The 2 beam depth is larger than the estimated ceiling jet depth (10% of 12 or 1.2 ft.), while the 1 beam depth should not be sufficient to fully block the ceiling jet, based on its estimated depth. Model Results The first significant result from the current modeling is that when the second beam pocket is completed and the 100 kw heat release rate is used for this particular scenario, the detector in the second pocket never reaches the alarm threshold. This result is in stark contrast with the assertion in the initial report, which states that this 100 kw fire should result in alarm of the detector in the second beam pocket if the complete pocket is modeled. This result can be clearly seen in Table 1 where detection times for the smooth ceiling spacing are given for three cases: no beams, 1 beams, and 2 beams.

Detector Cleary 1 Activation Cleary 2 Activation Heskestad L=1.8m activation time (s) Baseline 15 spacing 17 17 16 1 ft beams Detector (A) 9 8 6 1 ft beams Detector (B) > 600 > 600 > 600 2 ft beams Detector (A) 8 8 7 2 ft beams Detector (B) > 600 > 600 > 600 Table 1. 100 kw fire, 12 ceiling, 12 beam spacing results, 4%/ft sensitive detectors. As can be seen from the results, the smoke detectors at an x and y distance of 15 from the plume centerline in the baseline smooth ceiling case activated in 16-17 seconds after ignition. However, in both the 1 beam case and the 2 beam case, the detectors in the second beam pocket (Detector B) at the same distance from the fire as the smooth ceiling case failed to alarm within 600 seconds. Thus, even when a complete second pocket geometry is included to create the reservoir effect, the detector at the 15 spacing does not activate when either 1 or 2 beams are present. These results contradict the findings of the initial report, since the current modeling shows that the beams result in a substantially longer time to detector alarm than the baseline smooth ceiling case. The differences shown in Table 1 between the smooth ceiling case and the beamed ceiling case, when the smooth ceiling spacing is used as allowed in the revised version of NFPA 72 (2007 edition), are clearly outside the 60 seconds criterion that the initial work deemed to be significant. Therefore, the smooth ceiling spacing does not provide adequate safety for beamed ceilings in this configuration. However, as can be seen from Table 1, if a detector were included in every beam pocket (Detector A), as previously required by NFPA 72 (2002 edition), these detectors would alarm earlier than the detectors placed according to the smooth ceiling spacing. To further investigate the analysis of the initial work, the temperature threshold that was used as a surrogate for smoke detector activation was examined through the current models. Figure 3 shows plots of temperature rise vs. time for the three cases investigated with the 15 detector spacing. As can be seen in the figure, the top curve is for the baseline case of a smooth ceiling, the middle curve shows the temperature rise vs. time for the 1 beam case, and the bottom curve gives the temperature rise history for the 2 beam case. Also shown in the figure are the lower activation bound of 4 C temperature rise and the upper activation bound of 13 C temperature rise that was used for the temperature correlation. When the change in temperature at the smoke detector location reaches these thresholds, activation by smoke particles is assumed to have occurred.

20 18 16 14 Baseline - on ceiling 1ftbeams - on ceiling 2ftbeams - on ceiling Upper activation bound Lower activation bound Temperature Rise ( C) 12 10 8 6 4 2 0 0 100 200 300 400 500 600 Figure 3. 100 kw 12 ceiling, 12 beam spacing temperature results at the 15 spacing detector (Detector B). An examination of the three plots in Figure 3 shows that the baseline case exceeds both the lower and upper activation bounds within the first 10-15 seconds of the fire. The temperature plot for the 1 beam case exceeds the lower bound in approximately 15 seconds, but never exceeds the upper bound. In contrast, the temperature plot for the 2 beam case never exceeds the lower or upper bound for activation. Thus, these results show a significantly different outcome for the smooth ceiling case when compared with the beamed ceiling case. Similar to the results from the Smoke Detector Activation Algorithm, these temperature correlation results show that the smoke detector will quickly alarm for a smooth ceiling but likely will not alarm for a beamed ceiling if the smooth ceiling spacing is used. Again, this result contradicts the conclusion in the initial work that no significant difference in smoke detector alarm time will occur for the 15 spacing whether the beams are in place or not. Similarly, the authors of this paper examined activation times for the 15 spacing (Detector B) using the Geiman and Gottuk optical density correlation. Figure 4 provides a graph of optical density vs. time for the baseline smooth ceiling case and the two beamed ceiling cases. In addition, Figure 4 shows the upper and lower bounds for activation based on an ionization detector, as well as those for a photoelectric detector. The upper plot in Figure 4 shows the results for the baseline smooth ceiling case, the middle plot shows the results for the 1 beam case, and the lower plot shows the results for the 2 beam case.

Optical Density (OD/m) 0.16 0.14 0.12 0.10 0.08 0.06 Baseline - on ceiling 1ftbeams - on ceiling 2ftbeams - on ceiling Upper Ionization Bound Lower Ionization Bound Upper Photoelectric Bound Lower Photoelectric Bound 0.04 0.02 0.00 0 100 200 300 400 500 600 Figure 4. 100 kw 12 ceiling, 12 beam spacing optical density results at the 15 spacing detector. As can be seen from the figure, for the smooth ceiling case, the optical density of the smoke at the Detector B location exceeds both the photoelectric and ionization lower bounds within 20 seconds. However, for the 1 beam case, although the detector exceeds the lower bound for the photoelectric detector, it never exceeds the bounds for the ionization detector. In the 2 beam case, the optical density never reaches the lower bound for either the ionization or the photoelectric detector. Thus, similar to the previous results for the Smoke Detector Activation Algorithm and the temperature correlation, the current model shows that while the smooth ceiling detector will quickly alarm, the detector in the second pocket (Detector B) is unlikely to alarm in the presence of either 1 or 2 beams. These results show that conclusion in the initial work that the detectors did not alarm in their model of this scenario because of the incomplete pocket, i.e., lack of a reservoir effect, is unfounded. As the current model demonstrates, when a second full pocket is included and a 100 kw fire is used, the detectors still do not alarm based on a 15 spacing when either 1 or 2 beams are included, regardless of whether the SDAA, the temperature correlation, or the Geiman and Gottuk correlation is used. These results do not confirm the conclusion that the smooth ceiling spacing can be used for smoke detectors even when ceiling beams are present with no significant delay in detector activation, at least for this scenario. Further evidence that the detectors do not activate in the presence of ceiling beams when the smooth ceiling spacing is used is provided below by Figures 5 and 6. Figure 5 shows the exterior and interior detector chamber smoke obscurations in the

baseline case, along with the velocity. Figure 6 shows a similar plot for the case with 2 deep beams. All of the results above are for detectors that activate at 13%/m (4%/ft.) obscuration, which is an allowable threshold per UL 217. No beams (baseline) 15' 30.0 0.80 25.0 0.70 0.60 Smoke Obscuration (%/m) 20.0 15.0 10.0 5.0 Activation Threshold Baseline Exterior Smoke - 15' Baseline Heskestad 1.8m L Baseline Cleary I1 Baseline Cleary I2 Baseline Exterior Velocity 0.50 0.40 0.30 0.20 0.10 Velocity (m/s) 0.0 0.00 0 10 20 30 40 50 60 Figure 5. 100 kw 12 ceiling, baseline results at the 15 spacing detector (Detector (B)), both inside and outside the detectors.

2 ft beams (2-7a) In pocket 15' (Detector (B)) Smoke Obscuration (%/m) 30.0 25.0 20.0 15.0 10.0 5.0 2-7a Exterior Smoke - in pocket 15' 2-7a In pocket Heskestad 1.8m L 2-7a In pocket Cleary I1 2-7a In pocket Cleary I2 2-7a Exterior Velocity Activation Threshold 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 Velocity (m/s) 0.0 0.00 0 50 100 150 200 250 300 350 400 450 500 Figure 6. 100 kw 12 ceiling, 2 beam depth results at the 15 spacing detector, both inside and outside the detectors. As can be seen from Figures 5 and 6 above, the smoke obscuration at the smooth spacing ceiling detector (Detector B) in the baseline case reaches adequate smoke obscurations both inside and outside the detector. Conversely, in the 2 beams case, the smoke external and internal to Detector B does not reach adequate thresholds (13%/m or 4%/ft). This lack of adequate smoke at detector location B in the beamed ceiling cases is likely because the beams act to divert the flow of smoke away from detector location B to other adjacent pockets, so there is never a chance for these detectors to alarm to this fire. As discussed previously, a fire that ramps up instantaneously to 100 kw but then does not continue to grow may not provide the appropriate test for detector spacing. Therefore, the above analysis was repeated with a realistic medium t-squared fire. For these t-squared fire models, every other variable was left unchanged from the 100 kw case, except for the fire size and growth rate. Similar to the 100 kw cases, Table 2 shows the activation time results using the SDAA for the medium t-squared growth fire. Figures 7 and 8 show the activation times from the temperature correlation and Geiman and Gottuk s optical density method, respectively, using the smooth ceiling detector spacing location for both the baseline ceiling and the beamed ceilings.

Detector Cleary 1 Activation Cleary 2 Activation Heskestad L=1.8m activation time (s) Baseline 15 spacing 71 73 75 1 ft beams Detector (A) 43 49 43 1 ft beams Detector (B) 131 131 126 2 ft beams Detector (A) 48 48 58 2 ft beams Detector (B) 165 165 166 Table 2. 12 ceiling, 12 beam spacing results for a medium t-squared fire, 4%/ft sensitive detectors. 20 18 16 Baseline - on ceiling 1ftbeams - on ceiling 2ftbeams - on ceiling Upper activation bound Lower activation bound 14 Temperature Rise ( C) 12 10 8 6 4 2 0 0 100 200 300 400 500 600 Figure 7. 12 ceiling, 12 beam spacing temperature results at the 15 spacing detector (Detector (B)) for a medium t-squared fire.

0.20 0.18 0.16 0.14 Baseline - on ceiling 1ftbeams - on ceiling 2ftbeams - on ceiling Upper Ionization Bound Lower Ionization Bound Upper Photoelectric Bound Lower Photoelectric Bound Optical Density (OD/m) 0.12 0.10 0.08 0.06 0.04 0.02 0.00 0 100 200 300 400 500 600 Figure 8. 12 ceiling, 12 beam spacing optical density results at the 15 spacing detector (Detector (B)) for a medium t-squared fire. As can be seen from the graphs above, the results from the temperature and the Geiman and Gottuk correlations do not vary substantially from the SDAA results. For all three methods, in the baseline case, the detector at the smooth ceiling spacing (Detector B) activates at approximately 71-75 seconds, the detector in the 1 beam depth at the same location activates at approximately 126-131 seconds, and the detector in the 2 beam depth at the same location activates at approximately 165-166 seconds. Using the average activation time for each of these cases, the t-squared fire size can be calculated at the time of detector activation. On average, the fire sizes at activation in the three scenarios are presented in Table 3. Scenario Average Smooth Ceiling Spacing Activation Heat Release Rate at Activation (kw) Baseline (no beams) 73 62.5 1 deep beams 129.3 195.9 2 deep beams 165.3 320.2 Table 3. 12 ceiling, 12 beam spacing results for a medium t-squared fire showing fire size at activation as a function of beam depth. As can be seen from the table, if no beams are present, the fire is detected at a heat release rate of approximately 60 kw. But if 1 beams are included, the fire is not detected until almost 60 seconds later with a fire size over 3 times larger at approximately

200 kw. Finally, if 2 beams are included, the fire is not detected until over 90 seconds after the smooth ceiling case, and the fire size is over 5 times larger than if no beams were present, at over 300 kw. As a comparison, in Table 4 below, the activation times if a detector is placed in every beam pocket, as was previously required by NFPA 72, are displayed. Scenario Average Smooth Ceiling Spacing Activation Heat Release Rate at Activation (kw) Baseline (no beams) 73 62.5 1 deep beams in every pocket 45 34.8 2 deep beams in every pocket 51.3 30.8 Table 4. 12 ceiling, 12 beam spacing results for a medium t-squared fire showing fire size at activation if a detector is placed in every beam pocket. Table 4 shows that for the scenario of a 12 ceiling height and 12 beam spacing, if a detector is placed in every pocket, the activation time of that detector is approximately the same as that for a smooth ceiling spacing. Thus, if the old code spacing requirement were used, the time to alert occupants of a fire would be approximately the same for the beamed ceiling case as for the smooth ceiling case. Moreover, the fire size at activation would be approximately the same, regardless of whether the ceiling was smooth or had beams. This result is in sharp contrast with the previous result where the 2 beamed case resulted in activation more than two minutes later and only after the fire had grown to more than 5 times larger than the smooth ceiling case. Thus, the requirement of a detector in every pocket results not only in a time to detector activation as short as the smooth ceiling case, but also in detector activation at the same small fire size as the smooth ceiling case. Based on these results, the previous code provides much greater safety for occupants of a beamed ceiling room than the new version of the code provides. Summary and Conclusions Based on the results of the initial study, it was concluded that smooth ceiling detector spacing could be used for beamed ceilings with up to 2 deep beams without a significant reduction in time to detector activation. The authors of the current study chose one of the scenarios (12 ceiling, 12 center on center spacing) that would qualify under the new NFPA 72 requirements, modeled this scenario with smooth ceiling spaced detectors, and evaluated the difference in detector activation times for the beamed ceilings as compared to the smooth ceilings. The new model extended the geometry to include an entire second beam pocket. When these changes were made and the scenario was rerun with the current state of the art smoke detection sub-model (SDAA), significantly different results were obtained than those reported in the initial report. Specifically, when a 100 kw fire was modeled, one that the initial work indicates should be detectable within 60 seconds of when it would be detected if the beams were not present, the fire was never detected with the beams in place.

For a more realistic fire scenario such as a medium t-squared fire, the authors determined that a detector in every pocket will detect the fire in less time than the smooth ceiling configuration. Furthermore, if smooth ceiling spacing is used and the beams are in place, the fire at the time of detection will be at least (depending on single- or multiblock) 3 times larger if the beams are 1 in depth and will be more than 5 times larger if 2 beams are in place. The fire in the 1 beam case would be ~200 kw and in the 2 beam case would be ~300 kw, both of which are far larger than the 100 kw fire that was assumed should be detectable. As a result of this peer-review modeling and analysis utilizing the new SDAA in FDS, the new requirements in NFPA 72 (2007) that allow smooth ceiling spacing for some beamed ceilings should be reevaluated. References 1. Beyler, C. and DiNenno, P., Letters to the Editor, Fire Technology, v. 27, n. 2, 1991. 2. Cholin, J.M. and Marrion, C., Performance Metrics for Fire Detection, Fire Protection Engineering, n.11, 2001. 3. Cleary, T., Chernovsky, A., Grosshandler, W., and Anderson, M., Particulate Entry Lag in Spot-Type Smoke Detectors, Fire Safety Science - Proceedings of the Sixth International Symposium, 1999. 4. Geiman, J.A. and Gottuk, D.T, Alarm Thresholds for Smoke Detector Modeling, Proceedings of the Seventh International Symposium on Fire Safety Science, 2003. 5. Gottuk, D.T., Hill, S.A., Schemel, C.F., Strehlen, B.D., Rose-Phersson, S.L., Shaffer, R.E.., Tatem, P.A. and Williams, F.W., Identification of Fire Signatures for Shipboard Multi-criteria Fire Detection Systems, Naval Research Laboratory Memorandum Report 6180-99-8386, 1999. 6. Heskestad, G., Generalized Characterization of Smoke Entry and Response for Products of Combustion Detectors, Proceedings of the Fire Detection for Life Safety Symposium, 1975. 7. Luck, H. and Sievert, U., Does an Over-All Modeling Make Any Sense in Automatic Fire Detection? AUBE 99 Proceedings of the 11 th International Conference on Automatic Fire Detection, 1999. 8. McGrattan, K. B. and G. P. Forney. Fire Dynamics Simulator (Version 4), User s Guide. NIST Special Publication 1019, National Institute of Standards and Technology September, 2005 9. Mowrer, F.W. and Friedman, J., Experimental Investigation of Heat and Smoke Detector Response, Proceedings of the Fire Suppression and Detection Research Application Symposium, 1998.

10. O Connor, D.J., Cui, E., Klaus, M. J., Lee, C.H., Su, C., Sun, Z., He, M., Jiang, Y., Vythoulkas, J., Al-Farra, T. Smoke Detector Performance for Level Ceilings with Deep Beams and Deep Beam Pocket Configurations Research Project. NFPA Fire Protection Research Foundation Report, April, 2006. 11. Roby, R.J., Olenick, S.M., Zhang, W., Carpenter, D.J., Klassen, M.S., and Torero, J.L. Smoke Detector Algorithm for Large Eddy Simulation Modeling. NIST GCR 07-911, 2007. 12. Schifiliti, R.P. and Pucci, W.E., Fire Detection Modeling State of the Art, Fire Detection Institute, 1996. 13. Schifiliti, R.P., Fire Detection Modeling The Research Application Gap, AUBE 01 Proceedings of the 12 th International Conference on Automatic Fire Detection, 2001. 14. Wakelin, A.J., An Investigation of Correlations for Multi-Signal Fire Detectors, Masters Thesis, Worcester Polytechnic Institute, Department of Fire Protection Engineering, 1997.