Within the fire protection engineering field, life safety is a topic of great importance.  During the event of an emergency, such as a fire, the main objective of life safety is to allow people to evacuate an area before untenable conditions occur.  When designing high rise buildings, the time it takes for all of the occupants to evacuate must be calculated.  This time is known as the required safe egress time (RSET).  The time from the ignition of a fire until untenable conditions occur in the egress route or until an occupant is unable to self-evacuate is known as the available safe egress time (ASET).  Therefore, the RSET must be less than the ASET in order to guarantee life safety for the occupants.  However, the actual time it will take for all occupants to evacuate a building is a prediction assuming they all evacuate uniformly and at a constant speed.

In order to better understand human movement within stairwells and to obtain more accurate ways of measuring actual egress time, NIST has collected data on people movement within stairs of multiple high rise buildings during fire drills.  The data was collected from video cameras which were placed in various locations throughout the stairwells.  This data is being analyzed to understand the human movement and actual times of egress during evacuations.

One particular type of human phenomena that occurs when people evacuate in stairwells is that groups or “platoons” tend to form.  A platoon is defined as a group people who are spatially close and evacuate in a similar flow pattern.  However, there is very little research that has been done on determining how these platoons form or how they change as the occupants descend the stairwell.  Current research is being conducted to get a better understanding of the dynamics of these platoons during evacuation of high rise buildings.

Photo caption: “Building 5 stairwell showing typical landing, stairs up and down from the landing, handrails, and doorway from building floor to stairwell.”

When people are exiting a building in an emergency scenario, they travel from a given location to that stairwell on that floor, and then descend the stair until exiting the building. When the occupants first enter the stair on their original floor, they often encounter a flow of people descending from upper levels. This merging event has been found to affect both the velocity and flow rate of occupants descending the stairwell. However, little quantitative research has been done about this effect, and the factors which impact merging remain unknown. A better understanding of such merging phenomena will be extremely useful in building evacuation modeling, as well as in improving standards on building egress.

More Information

• Kuligowski, E. D. and Peacock, R. D., "Building Occupant Egress Data," Report of Test FR 4024, Natl. Inst. Stand. Technol., Gaithersburg, MD (2010).