Project Update: Study of the Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival

By: Keith Stakes and Robin Zevotek, P.E.

Research engineers with the UL Firefighter Safety Research Institute (UL FSRI) are currently leading a three year technology, research, and development project examining the impact of fire attack utilizing interior and exterior streams on firefighter safety and occupant survival. As research continues into how fire department interventions affect fire dynamics in the modern fire environment, questions continue to arise on the impact and implications of various suppression methods on both firefighter safety and occupant survivability. Previous research into different types of fire ground ventilation, flow paths, and exterior fire streams has provided the fire service with a more in-depth understanding of fire dynamics, while raising concern about certain fire attack methods. These concerns often stem from differing traditions and myths. This knowledge gap, and the lack of previous research in this area, has driven the need for further study into fire department interventions at structure fires, with a focus on hose streams and suppression tactics. On average, there are over 2,820 civilian deaths, and 13,780 civilian injuries annually in structure fires.¹  In addition, on average there are an estimated 35,743 fire ground injuries.²  These statistics underscore the need for further research into the various methods of fire attack that will allow for a broader understanding of how firefighter interventions on the fire ground can impact the outcome of both life safety and property protection.

The project is comprised of three parts:

• Part I: Air Entrainment and Water Distribution. (Fall 2015)
• Part II: Full-Scale Residential Fire Experiments. (Spring 2016)
• Part III: Acquired Structure Fire Testing. (Anticipated Spring 2017)

To gain a basic understanding of air flow and water flow, testing for Part I of the study was conducted without the presence of fire. Each test was designed to quantify the air entrainment in hose streams and determine where water is distributed within compartments. By evaluating the differences between a) various application methods, b) hose stream types, c) nozzle movements, d) pressures/flow rates, and stream locations and e) elevation angles, FSRI and the project technical panel were able to develop a fundamental understanding of air flow and water distribution. The results of the air entrainment and water distribution tests were then used to design more than 30 full-scale residential fire experiments. These experiments were conducted during the spring of 2016 in the laboratory at UL’s headquarters in Northbrook, IL. Each of the tests incorporated a specific type of attack, either interior or exterior, with differing ventilation configurations and varying hose line advances. Additionally, UL FSRI partnered with the University of Illinois to incorporate new measurement techniques on both moisture as well as victim skin burns to help further quantify the modern fire environment.

Air Entrainment Experiments

To determine the amount of air entrained by hose streams, several tests were conducted to gain a comprehensive view of how varying different components, either with the structure or equipment utilized, affected the end result. Engineers analyzed several key components including varying the setback distance from the nozzle to the ventilation opening, the hose stream type (straight stream, narrow fog, and smooth bore), and nozzle movement patterns (‘O’, ‘T’, ‘Z’, and inverted ‘U’). The testing was conducted at the Delaware County Emergency Services Training Center in Sharon Hill, PA.

Figure 1: Delaware County Emergency Services Training Center

Preliminary results yield that air entrainment is dependent on hose stream type, structure size/compartmentation/ventilation, speed of nozzle movement, and setback distance. Additionally, it was determined that differing nozzle movement patterns have little effect on overall entrainment regardless of nozzle type.

Water Distribution Experiments

Understanding water distribution from hose streams is imperative to understanding the effects of these streams on a compartment fire. A ‘one of a kind’ piece of equipment, typically intended for sprinkler density testing, was repurposed to sit beneath a constructed compartment to collect the water as it is applied to the compartment.

Figure 2: Water Distribution Testing Compartment

Experiments were conducted to determine differences in the water distribution from interior and exterior water application by varying hose stream types, pressures/flow rates, and nozzle movements. Results showed that water distribution is dependent on hose stream type and stream elevation angle. Additionally, it was evident that deflecting the hose stream off of the ceiling or walls during an indirect attack can be beneficial in surface cooling.

Full-Scale Residential Fire Experiments

Although a great deal of research has been done to understand the scalability of fire tests, there is no substitute for full scale fire tests. To conduct full scale fire tests evaluating fire attack, two 1600 ft², single-story, single-family homes were constructed to simulate the average of what would be seen in the United States. The test fixtures used modern construction practices and modern fuels to simulate a residential structure. The conditions within the fire buildings were monitored with over 250 instruments per structure to characterize temperatures, heat flux, velocity, and gas concentrations. Additionally, newly developed measurement techniques were utilized to gain insight into human skin burns as well as moisture measurements focused on steam production during suppression operations.

Figure 3: Furnished Living Room, Full Scale Fire Experiments

Figure 4: Attack Team Preparing for Interior Suppression

As the work continues on this project, several experiments will be conducted in the field in the early spring of 2017, where acquired structures will be instrumented and burned to examine the impact of a ‘room and contents’ fire transitioning to a structure fire. This will attempt to validate the work completed thus far to aid in firefighter safety and occupant survivability. Additionally, this work will provide those in the fire service with scientific-based principles and tactics to make informed decisions on the fire ground. The data and subsequent report from this study is anticipated at its completion during 2017. Stay tuned for the results.

This project was made possible through an award from the Federal Emergency Management Agency (FEMA) and the Department of Homeland Security (DHS) Assistance to Fire Fighters Grant Program, Fire Prevention and Safety Research Grant Program.

Keith Stakes and Robin Zevotek are with the UL Firefighter Safety Research Institute

References

¹ Michael Karter. Fire Loss in the United States During 2011. Tech. rep. National Fire Protection Association, Oct. 2012.

² Michael J. Karter and Joseph L. Molis. U.S. Firefighter Injuries - 2009. Tech. rep. National Fire Protection Association, Oct. 2010.