Air Entrainment Research

Pushing Fire Revisited

In my opinion the topic of “Pushing fire with water” is the single greatest piece of fire attack research which has been communicated poorly or misunderstood. UL is elaborating greatly and providing much better context/more clearly stated material for us to understand the early studies. If you have heard the phrase “you can’t push fire with water” don’t stop at this result or statement. There is much more to the story.


Do not take a snippet of information and tailor your training programs to provide the “latest fire attack research and recommendations”. Firefighters have a habit of taking research results (from multiple disciplines) and applying them to training exercises without context. That being said UL is also to blame for this miscommunication. Firefighters typically do not separate their discussions of water application and air entrainment during training. For many firefighters these are one in the same. Even though different patterns yield different results, some create more air entrainment and others much mess, there is no on/off switch to turn the air off at the nozzle.

Firefighters need to understand context, they need to understand the background and significance of these research projects. Reading the first and last paragraph of a 100 page research paper doesn’t provide you with a good foundation. It gives you results without context. To communicate as an instructor you need context and to translate that information into training and drills you need to understand the background and significance of these processes. Without context your drill becomes a training exercise prepped to fail. Adult learning typically happens in phases. 1. Rite, 2. Understanding, 3. Application, and 4. Correlation. Students participating in a drill need to get to the application phase and instructors need to live in the correlation phase. At the beginning of basic training we learn through Rite or memorization. We don’t quite grasp where or why and we have a hard time applying the skills during the initial phases of training. Once a student understands the skills we can apply those skills which provides a much better outcome. Skipping steps will only lead to confusion in the training process. Aaron Fields and I had a discussion one time and he provided me with a great teaching tool. He said, “If you have a student that says [I don’t see where this fits] you have missed the application phase of learning.” The student doesn’t understand how to apply the skill.

Lastly, just because you read it, watch it, or listen to it doesn’t mean it isn’t flawed. Research projects are very difficult to construct without some flaws. Most applied research projects literally have a section in the paper which explains the problems or flaws that might’ve occurred during the process. Make your drills purposeful, give them context, and your crews will perform at a much higher level. Follow the link below to understand this topic in much more detail. 



UL - Air Entrainment Research


UL's Firefighter Safety Research Institute has conducted an extensive Air Entrainment Study to evaluate the influence of nozzles and their ability to influence the flow path during a fire. I personally have been conducting my own back yard testing for more than a year on this very topic. From the moment "You can't push fire" was quoted I began to evaluate the entrainment of air using various nozzles and application techniques. I am looking forward to seeing the results UL publishes so we can have a better understanding of this dynamic environment. I will release several training videos in the near future about this very topic but until then check out UL's video about the study.


You can read below to see what UL has to say about this valuable research project:

As part of the 2013 DHS Grant to study the “Impact of Fire Attack utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival” testing was conducted at the Delaware County Emergency Services Training Center in Sharon Hill, PA to measure the amount of air being entrained into the structure by Fire Attack operations. Each test was designed to evaluate differences in entrainment, if any, by looking at different nozzle types, stream types, application patterns, as well as different compartment and ventilation configurations. These tests were conducted over a four day period where more than 150 tests were performed resulting in tens of thousands of data points as well as hours of video and hundreds of still images.

These experiments were conducted in a two-story residential structure with concrete walls and drywall constructing the first floor, and normal wood framing with drywall constructing the second floor. The building size was 20ft. wide, 36ft. long with 8ft. high ceilings. The building had multiple ventilation openings varying in size which allowed tests to be done utilizing different variables to replicate the most realistic conditions firefighters would face in the field. Additionally, the interior geometry of the structure was varied dependent on the type of test being conducted.

Instrumentation was used to measure air flow into the structure caused by the type of hose stream and how it was applied. These devices included bi-directional probes and associated pressure transducers to measure air flow in addition to in-line pressure and flow gauges to ensure the hose streams were applied at the desired pressure and flow per the manufacturer.

The tests covered a range of hose line sizes including 1-3/4” and 2-1/2” as well as different nozzle types: combination/fog and smoothbore. Portable monitor and master stream devices were examined as well. The hose streams varied between smoothbore, straight stream, and narrow fog in addition to the nozzle patterns including fixed, “Z,” “O,” and the Inverted “U.” The first round of experiments was aimed at determining the amount of air entrained by the different nozzles at different hose line sizes and application patterns irrespective of building configuration. The next series of tests examined the impact of varying the ventilation openings both behind and ahead of the nozzle. The final series of experiments focused on a more realistic interior geometry layout involving flowing water while moving down a hallway towards a room. Once again, ventilation openings were varied ahead of the nozzle. During each of these series of experiments, hose streams were applied from both the interior and exterior of the structure to determine the differences in overall entrainment into the structure.