NIST Technical Note 1839 Movement on Stairs During Building Evacuations Erica D. Kuligowski Richard D. Peacock Paul A. Reneke Emily Wiess Charles R. Hagwood Kristopher J. Overholt Rena P. Elkin Jason D. Averill Enrico Ronchi Bryan L. Hoskins Michael Spearpoint This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.TN.1839 NIST Technical Note 1839 Movement on Stairs During Building Evacuations Erica D. Kuligowski Richard D. Peacock Paul A. Reneke Emily Wiess Kristopher J. Overholt Rena P. Elkin Jason D. Averill Fire Research Division Engineering Laboratory Charles R. Hagwood Statistical Engineering Division Information Technology Laboratory Enrico Ronchi Lund University Lund, Sweden Bryan L. Hoskins Oklahoma State University Stillwater, OK Michael Spearpoint University of Canterbury Christchurch, New Zealand This publication is available free of charge from http://dx.doi.org/10.6028/NIST.TN.1839 January 2015 U.S. Department of Commerce Penny Pritzker, Secretary National Institute of Standards and Technology Willie May, Acting Under Secretary of Commerce for Standards and Technology and Acting Director Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. National Institute of Standards and Technology Technical Note 1839 Natl. Inst. Stand. Technol. Tech. Note 1839, 213 pages (January 2015) This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.TN.1839 CODEN: NTNOEF Abstract The time that it takes an occupant population to reach safety when descending a stair during building evacuations is typically estimated by measureable engineering variables such as stair geometry, speed, stair density, and pre-observation delay. In turn, engineering models of building evacuation use these variables to predict the performance of egress systems for building design, emergency planning, or event reconstruction. As part of a program to better understand occupant movement and behavior during building emergencies, the Engineering Laboratory at the National Institute of Standards and Technology (NIST) has been collecting stair movement data during fire drill evacuations of office and residential buildings. These data collections are intended to provide a better understanding of this principal building egress feature and develop a technical foundation for future codes and standards requirements. NIST has collected fire drill evacuation data in 14 buildings (11 office buildings and 3 residential buildings) ranging from six to 62 stories in height that have included a range of stair widths and occupant densities. A total of more than 22000 individual measurements are included in the data set. This report provides details of the data collected, an analysis of the data, and examples of the use of the data. The intention is to better understand movement during stair evacuations and provide data to test the predictive capability of building egress models. While mean movement speeds in the current study of 0.44 m/s ± 0.19 m/s are observed to be quite similar to the range of values in previous studies, mean local movement speeds as occupants traverse down the stairs are seen to vary widely within a given stair, ranging from 0.10 m/s ± 0.008 m/s to 1.7 m/s ± 0.13 m/s. These data provide confirmation of the adequacy of existing literature values typically used for occupant movement speeds and provide updated data for use in egress modeling or other engineering calculations. Keywords: Disabled, egress, egress modeling, evacuation, fire safety, human behavior, mobility impairments iii Executive Summary The time that it takes an occupant population to reach safety when descending a stair during building evacuations is typically estimated using measureable engineering variables such as stair geometry, speed, stair density, and pre-observation delay. In turn, engineering models of building evacuation use these variables to predict the performance of egress systems for building design, emergency planning, or event reconstruction. As part of a program to better understand occupant movement and behavior during building emergencies, the Engineering Laboratory at the National Institute of Standards and Technology (NIST) has been collecting stair movement data during fire drill evacuations of office and residential buildings. These data collections are intended to provide a better understanding of this principal building egress feature and develop a technical foundation for future codes and standards requirements. Chapter 2 includes a review of previous studies of occupant movement during building evacuations. At least three key features of these studies influenced the current study. First, much of the literature data is several decades or more old. There has been considerable discussion on the applicability of the older data with the assumption that current populations would be slower than that represented by the older data. Newly-collected data can be compared with historical data partly to assess the applicability of historical data to current building populations. Second, the literature data include only buildings up to 21 stories in height. Taller buildings were of particular interest. The buildings selected for study included a wide range of building heights. Finally, none of the literature studies include data beyond mean values or ranges of values. With more sophisticated egress models under development, this study endeavors to provide detailed data for model development and validation. This project provides a freely available set of raw data on evacuation-related people movement on stairs in the United States. The data of people movement on stairs consist of the times that each individual is observed by every video camera in every stair in every building observed by NIST (14 buildings total). Within the dataset, 11 of the 14 buildings were office buildings, and 3 buildings were residential. Of the residential buildings, two of the buildings (with a total of 172 evacuees) were exclusively labeled as assisted living facilities or elderly housing, which provided valuable evacuation timing data for people with mobility impairments and elderly occupants. A total of 5244 people (at a total of 173 camera locations) were observed over the 14 NIST-observed buildings, which ranged from 6 to 62 stories in height. A total of more than 22000 individual measurements are included in the data set. This report provides details of the data collected, an analysis of the data, and examples of the use of the data. The intention is to better understand movement during stair evacuations and provide data to test the predictive capability of building egress models. Measurements and Data Collection In this study, data from fire drill evacuations were collected by positioning video cameras out of the way of building occupants to record an overhead view of occupant movement in an exit stair during an evacuation. In most cases, video cameras were placed on specific floors throughout the iv building to capture a view of that floor’s main landing, the door into the stair at that level, and 2- 6 steps on each side of the main landing (leading to and from the main landing). This camera placement captured the times in which the occupant was seen moving past a particular floor landing as well as the time when he/she was seen moving into the stairs. Video cameras were placed at least every other floor, sometimes every floor, in each stair, with the exception of Building 6. Since Building 6 was a 62-story building, the number of cameras available for observation made it impossible to place cameras on every other floor in all four stairs. Therefore, cameras were placed nominally every 6 floors throughout each stair. Details of camera placement are available in section 3.1 and Appendix A. Data obtained from the video records included timing of each occupant as he/she entered and left every camera view and additional data such as the occupants location on the stairs and handrail usage. Finally, overall characteristics of the occupants such as gender, body size, floor of origin, whether he/she was carrying anything during evacuation, and whether he/she was assisting or being assisted by someone during the evacuation, were also obtained. Along with the movement timing, stair geometry including distance travelled on the stairs and landings, stair widths, stair tread depth, stair riser height, and landing size were measured in all of the buildings to allow calculation of delay moving to the stairs for evacuation, stair movement speed, density, and flow. The data collected and analyzed from these stairs, available on the NIST website at http://www.nist.gov/el/ fire_research/egress.cfm, is a primary output of this research and is intended as a resource for engineers and model developers. Pre‐Observation Delay Pre-observation delay was defined for each occupant as the time from the initial alarm until the occupant was seen entering the stair to evacuate the building. Across 30 stairs, the mean pre- observation delay of occupants was 230 s ± 53 s. Able-bodied participants had a mean time of 160 s ± 11 s before evacuating into the stairwell. The lowest delays occurred in building 12, with stairwell 12A occupants initiating evacuation after 35 s and 12B after 34 s. The quick pace could be attributed to low overall building population and building height as well as pre-announced evacuations. Stairs with mobility-impaired occupants began to evacuate after a longer period of time, 850 s ± 430 s. These facilities would normally have had higher delays than stairs with able- bodied occupants, having to wait for fire fighter rescue. Evacuees in Building 10, an assisted- living facility, had the longest delay at 1708 s. The extensive delay within the assisted living facility can be explained by the placement of several participants in stair descent devices before evacuation.