Firefighting, Truck Company

A New and Improved Tactical Decision Making Model, Part 2

By Richard Mueller

In my first article, I introduced the Fire Company 4’s (FC4’s) PREVIS2–OS tactical decision-making model. In this article, I will define and explore the model’s first two tactical components and explain how they earned their front-running tactical position.



The “P” of the PREVIS2 -OS model represents the action of performing a 360° perimeter evaluation. The perimeter component starts the decision-making model process by directing fire companies to obtain critical fireground factors intelligence before entry. Deliberately gathering critical incident factors is a bona fide tactic because, just like any other tactic, you must do something to accomplish it, i.e., a 360° size-up.

Critical incident factor information will not just fly into your head, you must go out and find it before it finds you (unprepared). However, not just any 360° size-up will do! Anyone can walk around a building. Only the fire companies that have prepared ahead of time for this trip will know and understand what transitional targets (visible rescue, exterior attack, fire location, structural profile, ventilation, and wind speed/direction) to look for and how to interpret what they find as meaningful action. Just as the quality of a ventilation tactic affects the fire attack tactic, and quality of a fire attack tactic affects the search tactic, the quality of the perimeter tactic can and does affect all other tactics. The 360° size-up provides the fire company with the first step in gathering more valuable information about the incident than from just the windshield size-up.

During the 360° size-up, the next three PREVIS2 -OS tactical components— visible rescue, exterior attack, and ventilation—can be identified, addressed, and performed before entry. Skipping the perimeter check delays visible rescues, the opportunity to “cool the box” before entry, and establishing an effective firefighting flow path in which to work. Wind direction, entrance and exit points, and the structural profile can then also be factored into the incident action plan (IAP). Performing the perimeter step of the model creates better decision-making that elevates mere amateur-level play into professional-level play.

So why don’t some fire companies perform a 360° size-up? I believe that a large part of the answer lies in our decision-making tools. This important fireground step (literally) is not part of either of the two most commonly used tactical decision-making models: REVAS or RECEO. So why are we surprised when a company does not attempt or conduct a 360° size-up if it is not part of its directions? The first step in building an effective fireground IAP is “some assembly required.” The perimeter step provides a time and place for a fire company to gather and assemble critical incident factors and an opportunity turn the incident “inside out” (make the interior more like the outside and the outside more like the interior) before entry. That is why taking the time to perform a perimeter check occupies the very first step in the PREVIS2-OS tactical decision-making model.



Saving lives is and always has been the most important priority of a fire company. Rescue is the tactic that saves the lion’s share of our customers at fire incidents. Rescue occurs in the transitional zone (collapse zone), and the need is identified and routinely discovered during the 360° size-up. Here, occupants are located by sight and sound, typically from windows or porches, and by calling out for a response into openings created for entry and exit. When occupants are located, rescue tasks are immediately implemented to remove them from harm.

The rescue priority has historically included both the rescue of visible occupants and search and rescue of nonvisible occupants. When dispatched with or notified on arrival that someone is inside, you must choose between going in and searching or attacking the fire. When multiple companies are present, it’s an easy call because you can accomplish both at the same time. However, when you are operating by yourself (single company) you must choose between fire attack and search and rescue. FC4’s PREVIS2-OS model, based on a single company operating for the first 10 minutes, divides the rescue priority into visible rescue (rescue) and nonvisible rescue (search and rescue). Most of the time, visible rescue is addressed and accomplished first as a part of the Perimeter step, and nonvisible search and rescue is physically accomplished after interior fire control. However, occasionally, a visible rescue may wait when a quick knockdown from the outside (transitional attack) is possible or when faced with situations like a large apartment complex with many people at windows. Some of the not “immediately endangered occupants” will and should wait for rescue when the opportunity for an exterior/interior attack can be effectively performed.

Additionally, some nonvisible rescues may have to be attempted from the outside (enter, isolate, and search) when faced with obvious defensive conditions. The PREVIS2-OS tactical decision-model gives nonvisible occupants and firefighters the highest priority of life safety by mechanically and quickly creating and maintaining survivable interior atmospheres by using positive pressure ventilation (PPV) and transitional fire stream application. (Remember the temperature drop rates in the transitional strategy.) These actions allow the fire company to quickly search for viable victims in the PPV flow path on the way to the fire and after fire control. We create an environment that is survivable first by controlling the fire, removing smoke, heat, and humidity and then locating and removing nonvisible sustained occupants. A little fire attack up front can go a long way toward a more effective and successful operation with search.

When fire companies choose search ahead of attack they are betting that they can find the occupants before conditions deteriorate, preventing them from completing their mission. This is a bet that has resulted in too many National Institute of Safety and Health (NIOSH) Fire Fighter Fatality reports, Fire Fighter Close Call incidents, and fire occupants who do not survive.

Research by Underwriters Laboratory (UL) has demonstrated that a search company may have as little as 100 seconds to search after entry before conditions are untenable to the company members, and that flashover can occur less than 10 seconds later. The time when conditions become untenable to unprotected occupants is obviously even less. The brutal truth is that one civilian every three hours lose this bet every day. In fact, the odds are so bad that the fire service doesn’t even track its success rate. Just try to find out how many nonvisible occupants firefighters found, removed, and survived “search” last year? Although we clearly know our failure rate, we have no idea of our success rate. Why do we continue to make tactical priority decisions based on our failures rather than on our successes?

Plastic- and foam-based furnishings, lightweight and engineered building products, and open concept floor plans do not have a long life span when exposed to fire, much less long, drawn out searches. For life safety, using the PREVIS2-OS model and applying transitional fire streams and PPV before entry, fire companies are more honestly performing search and rescue rather than search and recovery to nonvisible occupants by creating a more survivable atmosphere. (Remember the survivability profiling information in the marginal strategy?) People and pets have a dismal survivability profile when exposed to highly toxic smoke and low-to-moderate heat levels, even for short periods of time.

The FC4 PREVIS2-OS tactical decision-making model acknowledges that it is more effective (survivable) to quickly slow, reduce, or even put out the fire first before searching, finding, and removing the nonvisible occupants from the hazard. Far too often, firefighters abandon controlling the fire before search when presented with incident information that someone is or may be inside. My experience as well as research done by Stephan Marsar has shown that this turns out to be a false positive, and overwhelmingly so. This is also the false negative case where someone tells us that no one is home or inside when someone actually was. Either way, both scenarios require a primary and secondary search and can cause us to question our actions for many days, months, or even the rest of our careers when we were mislead or guessed wrong.

I believe that fire companies should stop guessing and be the first ones to believe that someone is inside; they also should be the last ones to say that there isn’t someone inside at all incidents. As a result, all of your fire attacks (IAPs) will be based on thinking and actions to complete a successful search rather than being denied one because you didn’t properly prepare for the fire, allowing the fire to win.

Firefighting is never a fair fight; it always gets a head start. Why would you not try to even the odds for you and any occupants by slowing the fire down by transitional attack and speeding up your pace with flow path firefighting in the race to save occupants? I believe that too often it is because we trade fire science for fire emotion; we make decisions guided by untrained fire spectators such as owners and occupants rather than from fire scientists.

When we control our atmospheres, they will not control us. Fast extinguishment and dilution and removal of heat, smoke, and humidity are essential to occupant survival and the methods used to accomplish this need to be started early. These efforts create and maintain higher survivability profiles for anyone inside of the structure including the firefighters themselves who are able to perform the tasks of interior fire attack and search and rescue more effectively. An aggressive exterior attack as well as venting ahead of the interior attack enables the fire company to search more quickly and effectively while attacking the fire. Improving and maintaining visibility allows occupants who are unable to escape on their own the highest “benefit of the doubt” of survival because of a less toxic atmosphere, reduced heat, and an increase in visibility that allows rescuers to locate them faster. Visibility also sets the stage for more rapid (higher performance) “under control,” and “all-clear” benchmark times.

It has been my experience, observation, and research that when searches are performed ahead of attack, more negative consequences such as death, damage, disease, and firefighter error result than if the search would have been performed first by atmosphere control rather than by fire company manual labor. While this may be unsettling for some, if you ask yourself and honestly answer the question of “How many nonvisible fire occupants in your neck of the woods are saved vs. just recovered?” I think you would have to admit that the number is overwhelmingly low. Although I know that some have successfully searched for and rescued nonvisible occupants without first performing a 360° size-up and attacking fire and/or providing effective ventilation before entry, the latest data—3,005 fire deaths 2011—memorializes the fact that many, many more were not.

If we want to change this and save more fire occupants and prevent more firefighter deaths and damage, then we have to start taking control of the interior atmosphere sooner. An aggressive exterior attack and venting ahead of interior attack, especially with positive pressure, creates more survivable environments. When additional companies arrive on scene, the PREVIS2-OS model is then addressed from back to the front, speeding up the nonvisible search component (the second-in company would be assigned the primary search). The sooner that more companies arrive, the faster tactical implementation of the model can be completed.

In my next article I will address the two middle steps: Exterior Attack and Ventilation.

Photo found on Wikimedia Commons courtesy of Elner Helland Berger.



Karter Jr, M.J. Fire Loss in the United States during 2011. National Fire Protection Association. September 2012.

Kerber, S. Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction. Underwriters Laboratories. December 14, 2010.

Kerber S. and William D. Walton. Effect of Positive Pressure Ventilation on a Room Fire. Federal Emergency Management Agency 7213. March 2005.

Corbitt, Given, Martin, et al. “Respiratory Burns; a correlation of clinical and laboratory results,” Annuals of Surgery, Emory University. Atlanta, Georgia. 1967.

Liu, Young-Gang, and Zang. “Theoretical evaluation of burns to the human respiratory tract due to inhalation of hot toxic gases during early stages of fire.” Burns 32, Issue 4, Vol. 32, 2006. Elsevier Ltd. 32:436-446. San Diego, California.

To Hell and Back IV: The Toxic Twins (DVD). People’s Burn Foundation. Indianapolis, Inidana. September 2009.

Marsar, S. “Survivability Profiling: Are the Victims Savable?” Fire Engineering. December 2009.

Marsar, S. “Survivability Profiling: How long can victims survive in a fire?” Fire Engineering. July 2010.

Mueller, R. Are You “Four” or Against Strategy? Part 3. March 20, 2013.   


Richard Mueller is a retired battalion chief for the West Allis (WI) Fire Department. He is a fire instructor for Waukesha and Gateway Technical College and a technical rescue instructor for the WI REACT Center. He is a member of the Federal DMORT V and WI Task Force 1 Team and a Partner with the WI FLAME Group. He is the author of the firefighting textbook Fire Company 4 and can be reached at [email protected]