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

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

Evaluating fire attack methods and their effect on firefighter safety and occupant survivability.


This three-year study builds on previous research on fire service ventilation and suppression tactics (e.g., interior suppression versus “transitional attack”) to provide a comprehensive assessment of firefighting tactics on chemical and thermal exposures for victims trapped within a structure, and firefighters advancing toward the fire or operating in other parts of the structure.

While research at UL and NIST has shown transitional attack to be a viable option for rapid knockdown of a large volume of fire, there remains some hesitation about adopting the tactic for fear of endangering trapped victims and pushing heat and steam. Fire service adages such as “don’t put water on smoke” and “you will steam the victims” are examined in detail in the context of today’s modern fire environment to provide credible scientific information that can improve decision making on the fireground. Using full-scale residential structures in UL’s large fire laboratory in Northbrook, IL, several different fire scenarios are tested using tactics that include interior only and combined interior/exterior fire attack. The research generates important fire data that includes temperatures, heat flux, flow velocities, differential pressure, gas concentrations, and moisture content throughout the structure and provides knowledge on how flow paths and conditions in the structure are impacted with nozzle pattern selection and nozzle movement during fire suppression operations.

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The experiments conducted in support of this project were split into three categories: water mapping, air entrainment, and full-scale experiments. Water mapping and air entrainment experiments can be considered to be cold-flow experiments. The experiments were conducted in the absence of fires to develop a more fundamental understanding of the topics. The full-scale experiments combined what was learned during the cold-flow experiments and applied that knowledge to live-fire experiments in a ranch-style residential structure. 

Water Mapping

The goal of the experiments was to quantify water distributions within a room over a set of parameters typically used in the fire service. In all the experiments conducted, it became clear hose streams effectiveness is limited to line of sight. The results show the momentum from fire service hose streams prevents the stream from bouncing off a surface. Using a steep angle directed at the ceiling of a compartment was shown to coat the most surfaces and provide distribution along all four walls. As the angle decreased, the amount of surface coating decreased. This was consistent regardless of the nozzle type, pattern, or even the direction the water was applied from. Understanding this fundamental principle of water dispersion can aid firefighters in understanding how to apply their water during fire suppression operations most effectively.

For more detailed information and discussion on the tactical choices regarding water mapping, check out the ONLINE TRAINING COURSE

Air Entrainment

The results from these experiments show that to increase air entrainment, a firefighter should create a more broken stream or fog pattern, move the nozzle rapidly, and provide the largest stream length. If the intent is to limit air entrainment, the nozzle firefighter should use a fixed nozzle position on a smooth bore or straight stream and limit the stream length where possible. Noticeable differences were seen between air entrainment from a smooth bore stream versus a straight stream. Ultimately, understanding these key concepts of air entrainment can aid firefighters in being more effective.

For more detailed information and discussion on the tactical choices developed from this air entrainment research, check out the ONLINE TRAINING COURSE

Full-scale Experiments

More than 15 tactical considerations were developed from the 25 full-scale, live-fire experiments focused on suppression operations. The considerations provide data-driven insight into interior advancement techniques (i.e., flow and move versus shutdown and move), the impact of water flow on gas movement with a flow path, interior and exterior water application, and the impact of gas contraction during water flow, among other topics. For more detailed information and discussion on the tactical considerations developed from the research, check out the ONLINE TRAINING COURSE

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