The prediction of human behavior during a fire emergency is one of the most challenging areas of fire protection engineering. Yet, understanding and considering human factors is essential to designing effective evacuation systems and ensuring safety during a fire and related emergency events. Here are some of the current issues in the topic of human behavior in fire.
SFPE Guide to Human Behavior in Fire, 2nd Edition Now Available
This single resource for the fire safety community distills the most relevant and useful science and research into a consensus-based guide whose key factors and considerations impact the response and behavior of occupants of a building during a fire event.
The Second Edition of SFPE's Engineering Guide: Human Behavior in Fire provides a common introduction to this field for the broad fire safety community: fire protection engineers/fire safety engineers, human behavior scientists/researchers, design professionals, and code authorities. The public benefits from consistent understanding of the factors that influence the responses and behaviors of people when threatened by fire and the application of reliable methodologies to evaluate and estimate human response in buildings and structures.
This Guide also aims to lessen the uncertainties in the "people components" of fire safety and allow for more refined analysis with less reliance on arbitrary safety factors. As with fire science in general, our knowledge of human behavior in fire is growing, but is still characterized by uncertainties that are traceable to both limitation in the science and unfamiliarity by the user communities. The concepts for development of evacuation scenarios for performance-based designs and the technical methods to estimate evacuation response are reviewed with consideration to the limitation and uncertainty of the methods. This Guide identifies both quantitative and qualitative information that constitutes important consideration prior to developing safety factors, exercising engineering judgment, and using evacuation models in the practical design of buildings and evacuation procedures. Besides updating material in the First Edition, this revision includes new information on:
- Incapacitating Effects of Fire Effluent & Toxicity Analysis Methods
- Occupant Behavior Scenarios
- Movement Models and Behavioral Models
- Egress Model Selection, Verification, and Validation
- Estimation of Uncertainty and Use of Safety Factors
- Enhancing Human Response to Emergencies & Notification of Messaging
The prediction of human behavior during a fire emergency is one of the most challenging areas of fire protection engineering. Yet, understanding and considering human factors is essential to designing effective evacuation systems, ensuring safety during a fire and related emergency events, and accurately reconstructing a fire.
The guide is available through Springer in hardcover format or as an e-book by going to https://www.springer.com/us/book/9783319946962.
Modeling Human Behavior in Fire
As noted by Gwynne in the Quarter 4, 2017 issue of Fire Protection Engineering magazine, it is important to create accurate evacuation plans for buildings and this is often done using modeling. Any attempt to understand, describe, constrain, account for, influence or assess evacuee behavior involves the use of a model. This is a powerful tool, but its abilities should be viewed with some skepticism.
The most common type of modeling is the evacuation computer simulation tool. Users should consider the competency behind these models especially when the user doesn’t have full control over all of the inputs. Another popular type of modeling is the engineering hand calculation. However, this model focuses entirely on physical performance and ignores factors such as non-movement behaviors. A third model is the evacuation drill. In theory this is a good way to predict evacuation times but these drills are somewhat limited compared to evacuation in an actual fire. Among other limitations, they often involve sub-populations with prior knowledge and may not address the most vulnerable sub-populations exposed to the riskiest scenarios. Prescriptive regulation is another approach to evacuation modeling. There are evacuation models embedded within each prescriptive regulatory code. However, the assumptions used to create these models may be inconsistent in some situations and the detailed assumptions themselves may be hard to find since they are not always included in the code. The final model considered is the understanding/perspective of evacuee behavior. Individuals have different opinions on how people will behave in a fire. These can sometimes be accurate but often times they are biased by dramatic media portrayals of events.
Occupant evacuation elevators (OEE) became an option in 2012 when the IBC allowed them to be used in place of a redundant egress stair for buildings over 420 feet tall. As noted by Maddox in the Quarter 4, 2017 issue of Fire Protection Engineering magazine, evacuation elevators allow for faster egress, accommodations for the disabled, and more room on the stairs for fire fighters. It is predicted that 25% of the building population will use the elevator for egress so according to the IBC, elevator lobbies must be large enough to accommodate 25% of the anticipated population on each floor.
The use of OEE can be more cost effective than redundant stairs, especially in slender buildings, however they have other ramifications. Each elevator lobby must be adjacent to a star enclosure or have access to a stair enclosure with a 1-hour protected corridor, which complicates the design of the buildings core. Also, every elevator in the building must be simultaneously provided with standby power which requires a large generator system, and the power and control wiring for these elevators must be protected. Additionally, the OEE and fire service access elevators must be equipped with water protection so that no water may enter the elevator lobby (in California). According to tests done by the San Francisco Fire Department, trench drains and waterproofing the walls of the lobby are the most successful way to achieve adequate water protection. The use of OEE also requires a control panel that shows information about the elevators locations. The wiring to the fire alarms and this control panel must be protected as well. If the elevator lobbies are treated as stair vestibules (as they commonly are) they require pressurization to be smokeproof.
If the elevators are in automatic operation in the event of a fire they will evacuate the fire floor first and then the adjacent floors until a five-floor block has been evacuated. In manual evacuation mode, the elevators will evacuate the fire floor first then other floors in the evacuation zone based on distance from the discharge level. It is also required that real time messages be displayed in the elevator lobbies with information about the elevators location. Additionally, it is important to consider that all elevator evacuees will be exiting through the main lobby and this should be accounted for. The use of OEE is expected to increase dramatically in the future as models prove it to be a faster and safer method of egress.
Evacuation of Health Care Facilities
Emergency evacuation of healthcare facilities is particularly challenging because of the vulnerable population. As noted by Hunt in the Quarter 4, 2017 issue of Fire Protection Engineering magazine, patients may require care and assistance through the evacuation process, which puts a lot of pressure on the staff to successfully evacuate the entire facility. This is even harder because practicing evacuations is very uncommon due to its impracticality, cost, and ethics. However, as the population ages, planning must consider more people with movement impairments than ever before. The most common strategy is progressive horizontal evacuation, where patients are moved into adjacent fire-resistant compartments away from the fire. Sometime horizontal evacuation is not enough and a full building evacuation is required. Unfortunately, the perception that horizontal evacuation is sufficient has led to gaps in planning and provision in training and equipment.
The success of hospital evacuation is dependent on the time it takes to evacuate as well as the time the fire protection features can last. Planning requires the designer to predict a required safe egress time, but this can have a large degree of uncertainty depending on the patient movement devices used. There are only a few data sets available to quantify the performance of these devices. To make calculations more accurate, assisted movement devices have been added to computational evacuation models. However, there is still room for improvement as these models don’t account for the shape and increased footprint of movement devices.
Progress is headed in the right direction but there is still a lot that needs to be done to improve the process of evacuating vulnerable populations.
SFPE Engineering Guide to Human Behavior in Fire