More Research Is Needed to Relate Demographics and Human Behavior in Fire

By Bryan Hoskins, PhD, PE

 When considering human behavior in fire, the intent is to make sure that system design facilitates life safety. That requires an understanding of what people will do and why they behave the way that they do in a crisis such as a building fire. If the data underlying the design do not match the situation to which they are applied, the system may not function as intended.

Buildings are constantly increasing in size and complexity. This will result in increasing the required safe egress time for individuals within a building. When an evacuation is needed, whether due to fire, natural disasters or other events, the building egress systems must be designed to allow people to move efficiently from their initial positions to a location of safety. An underlying assumption in model codes is that people who are not familiar with fire shall be kept safe from the effects of a fire. To ensure that people are kept safe, it is essential to understand how long people require to evacuate or relocate safely within a building.

The formulas and calculation methods that are commonly used to predict movement speeds are often based on data collected nearly 50 years ago. In the 1960s and 1970s, Jake Pauls (1980) collected his data in Canada, typically in cities like Ottawa, and John Fruin (1971) collected his data in New York City. Most of these studies were conducted in office buildings and mass transportation facilities. The societal norms in those cities was for people to be riding the subway daily and then walking to their offices — a relatively active population. Furthermore, most of the data were collected in buildings that were less than 15 stories tall. Thus, most of the data are for people who had to travel short distances within the stairwells to escape a fire.

Older data would not be problematic not only if buildings were of similar smaller sizes, but if people of today still behaved similarly to the populations in the original studies. More and current data must be collected to determine how much movement speeds have changed. Several factors could contribute to significant changes in those speeds.

First, obesity is increasing throughout the world, which could affect movement speeds in two ways. In egress components like stairs, individuals taking up more space could make passing much harder than it used to be. Pauls (1980) found that slower-moving individuals did not disrupt the overall flow because others could pass them easily, but this may not the case if there is no longer sufficient room to move past individuals who take up more space than others. People who are obese also might move at slower speeds than have been predicted.

Second, the workforce is more diverse now than it was 50 years ago. People are living, and working, longer. More people with disabilities are in the workforce than in the past. Some individuals who are elderly or have disabilities can move at the same average speed, or faster, but others will move more slowly. On average, movement times of elderly and disabled people are slower than the overall population (Fruin, 1971; Boyce, et al., 1999).

Third, cultures throughout the world could be different from the northeastern part of North America. Other regions could have societal norms that lead to slower movement speeds. There also could be differences in familiarity with egress systems based on people in different areas using the stairs more or less than seen in the original studies. In addition, the amount of personal space that people expect is different throughout the world, so some locations may experience different movement speeds at a given density.

Finally, calculations like the ones provided in the SFPE Handbook typically use the average values from the data to predict movement speeds. Even with values that are representative of the overall population, relying on average values has the potential to provide insufficient time for vulnerable populations.

All of these factors have the potential to lead to slower movement speeds than in the past, so new data must be collected to design egress systems that accommodate the needs of modern populations.

Some more-recent research has looked at vulnerable populations and the movement speeds of individuals (Boyce, et al., 1999), residential occupancies (Proulx, 1995), and more-modern populations (Kuligowski and Peacock, 2010). These studies and others have provided some insight into how movement speeds might be changing.

In some cases, the movement speeds of some vulnerable populations is based on five or fewer individuals moving by themselves. If those individuals are not representative of the range of movement speeds for that population, then those numbers may over-predict the actual movement speed needed to attain safety. How people behave within the larger group, and the impact that they have on the overall flow, cannot be captured by studying them in isolation.

Similarly, the studies that look at different regions or types of occupancies tend to be based on only a few evacuations. If those buildings are not representative of the overall population, then there is also the potential that movement speed will be over-predicted.

Clearly, more data are needed.

Bryan Hoskins, PhD, PE is with Oklahoma State University Fire Protection and Safety Engineering Technology.

References

Boyce, K.E., Shields, T.J., and Silcock, G.W.H., Toward the Characterization of Building Occupancies for Fire Safety Engineering: Capabilities of Disabled People Moving Horizontally and on an Incline, Fire Technology, Volume 35, Number I, 1999, pp. 51–67.

Fruin, J.J., Pedestrian Planning and Design, Metropolitan Association of Urban Designers and Environmental Planners, Inc., New York, NY, 1971.

Kuligowski, E.D., and Peacock, R.D., Building Occupant Egress Data, Report of Test FR 4024, National Institute of Standards and Technology, Gaithersburg, MD, 2010.

Pauls, J.L., Building Evacuation: Research Findings and Recommendations, in Cantor, D., Ed., Fires and Human Behaviour, John Wiley & Sons, New York, NY, 1980, pp. 251–275.

Proulx, G., Evacuation Time and Movement in Apartment Buildings, Fire Safety Journal, Volume 24, Issue 3, 1995, pp. 229–246.