Ventilation-Limited Fire: Keeping it Rich and Other Tactics Based Off Science

By P.J. Norwood and Frank Ricci

Scientific research and data is critical to increase our understanding of the dynamic environments we face as firefighters. However, it is important that the message does not get lost in the noise. Although our service has been attempting to reconcile the Underwriters Laboratories (UL) and National Institute of Safety and Technology (NIST) studies, we will focus on the practical application.

We have found that the new understanding is not as scary as it seems. What we consider as new is based off tactical pieces of the puzzle that have been in practiced by experienced truck and rescue companies for years.

No, we are not talking about the engine member who is riding the truck and getting his first taste of breaking windows indiscriminately! We are talking about how venting and limiting venting has to be coordinated. There is no change; tactical discipline is and has always been critical in controlling the building. What we are learning is that it is even more important than we thought, and the fire behavior model of the past is not the same model of today.


Flow Paths and Fire Behavior

The Great Vertical Ventilation Debate Rekindled: Lightweight Construction and Vertical Ventilation

Ventilation-Limited Fires and the Influence of Oxygen

Searching in the Flow Path

Video: Working in the Flow Path

As we discuss the UL and the NIST studies, we are finding that the latest science has just given us the full picture to link understanding and improve on our tactical disposition.

Terminology is critical to understanding. However, just because an event has a new name doesn’t mean it is something altogether different. A fuel-limited fire is no different than a fire that is producing high volumes of smoke that firefighters were taught not to break windows until the line was applying water. We have called this “keeping it rich.” This practice should continue with a better understanding of the implications of your actions and inactions. The fact is the fire environment has become less forgiving. As an example in truck school, we were taught not to vent before the application of water. We have all witnessed a member taking windows indiscriminately in violation of this rule and getting away with it. Now, we are seeing these faults resulting in catastrophic consequences.


Fire Behavior

We all understand that building construction and home contents have changed. Furniture has become the equivalent of solid-state gasoline. Long gone are the days of wood and natural fibers. What some may not understand is how today’s contents and building materials are affecting fire behavior.

The traditional fire behavior model we have all learned to understand is outlined in figure one below courtesy of UL’s Firefighter Safety and Research Institute.


Figure 1. Traditional Fire Behavior Fuel Limited Fire.


The traditional fire behavior model still works today for a fuel limited fire similar to a pile of pallets in your department’s burn building. However, most of the fires we face today are not fuel limited.

Today we are experiencing a fire behavior model as illustrated below:


           Figure 2. Typical Structural Fire Behavior Ventilation Limited Fire


Today’s fires are becoming ventilation limited, which at times occurs before the first companies arrive. Therefore, when we force entry, a window fails, or air is introduced into the structure, we see a rapid acceleration of energy and a heat. During the many UL tests, it was found that time of ventilation to untenable conditions in a one-story home was 1 minute, 40 seconds and in a two-story home it was 3 minutes, 20 seconds. Both scenarios should be utilized as an order of magnitude as times can be shorter or longer based off different circumstances. Remember, ventilation is any action that allows smoke out and air into the structure. When air is allowed in or out of a structure, we are feeding the flow path and increasing the energy to the fire.

Ventilation Limited FireA fire in which the heat release rate and fire growth are regulated by the available oxygen within the space. (Fire Department of New York [FDNY] Procedures Volume 1, book 10.)

Outside Vent Team—Simply, when venting for fire, the water must be applied to the fire before your team takes out windows. Once water is applied to the main body of fire, the first windows to be taken should be in the fire room; then, work back.

Indiscriminately venting before the fire is being controlled could create untenable conditions, forcing the attack crew out of the building. This is especially dangerous if you vent behind the line lighting up the entire hallway. Smoke is just fuel waiting for you to make a mistake.

 (1) No additional windows should be taken until signs of suppression are visible. (Photo courtesy of


For an example, refer to photo 1. Venting additional windows before the line is applied could result in ventilation-induced flashover. Temperature increase can be greater than 1,000°F. This action must be coordinated. You must be patient and have vent discipline. This coordination can occur by radio or by paying attention to the signs of suppression.

Recommendation 1: When venting for fire, the attack line must be in place at the main body of fire. 


Flow Path

At this point, do not be surprised that we must discuss the terminology flow path and how it affects “Keeping It Rich.”

Flow path is defined as the movement of heat and smoke from the higher pressure within the fire area toward the lower-pressure areas accessible by doors, widow openings, and roof structures. Generally, unless the thermal layering is disturbed, hot air travels out on top and cool air travels in on the bottom.

As a firefighter, it is critical you understand what the flow path is and the results of being within the flow path.

Heated fire gases are moving toward the low-pressure areas; based on varying building designs and the available ventilation openings (doors, windows, and so on), the fire’s energy is pulling in additional oxygen from the low-pressure areas. Note that there may be several flow paths within a structure. Any operations conducted in an uncontrolled flow path without an attempt to limit the velocity of the flow path could place the members at significant risk because of an increased in movement of fire (heat and smoke toward their position). The speed of convention heat and smoke has been measured at up to 15 miles per hour (mph). You cannot out-crawl the flow path. Therefore, you could become trapped within this hostile environment, sustaining serious injuries or even death.

 (2) The door still must be controlled in the almost closed positions and line was stretched in charged. Stationing a firefighter at the door is the recommended practice. 


Recommendation 2: By controlling the flow path and the amount of air entrained in the structure, you are limiting the amount of energy available for the fire.

Recommendation 3: Stretch a charged line from the point of entry on the fire floor. There is no excuse to stretch dry on the fire floor.



Experienced firefighters have considered flow path with out even knowing it while performing the truck search and vent-enter-search (VES) for years. Many truck firefighters have been closing doors during their unprotected search. Yes, we now call it vent-enter-isolate-search (VEIS) to be clear. VES and door control has been part of that tactic for more than a decade.

When you are conducting conventional search tactics, flow path should be the key consideration. Since 2007, we have advocated on a national level that when the firefighter enters a bedroom, he must close door behind him. The fire cannot tell the difference between VEIS and conventional tactics.

There are also many advantages to closing the door. First, create an area of refuge. Second, when you or your partner vents for life, no flow path will be created. The smoke in the room will also lift, reducing carbon monoxide (CO), hydrogen cyanide (HCN), and a host of other nasty actors. Visibility will increase, facilitating a quicker search.

Now, when you open the door, you must understand that you are now in a flow path. If the line is in place and applying water, you can chock the door open to aid in ventilation. If the line is not in place, have your partner leapfrog into another bedroom and close the door to the room (which is already searched) and move to your partner’s new area of refuge. By closing doors and conducting protective searches, we should see a reduction in the amount of firefighters forced to bail out windows.

Recommendation 4: The old tactic of checking for deteriorating conditions with the door open to the room being searched should be taken out of the books.

Recommendation 5: When venting for life, you must be able to isolate your position. If you cannot, then you cannot vent windows. Note that in most cases this means windows in the kitchen and living room cannot be vented until water is being applied to the fire.

Hostile Search—View an instructional video of the Hostile Search at Fire Engineering’s “Training Minutes” at

Hostile searches typically consist of bathroom and fire room searches that pose a higher risk because of a lack of egress and proximity to the fire. FDNY’s Vincent Dunn taught us to not go further than five feet when flashover is possible. The rule is based on how the average firefighter crawls 2½ feet per second. That is equivalent to 1.7 mph. As previously stated, flow path can travel at speeds of up to 15 mph. We do not recommend conducting a free search without having a guarantee that you can control the door to the room. Plastics are producing high volumes of black smoke, making visibility even more limited than in the past. Rollover used to be a reliable sign of impending flashover, but now we find that this sign can be masked by black smoke.



Recommendation 6: When conducting a hostile search, hook your foot on the doorframe. This way, if conditions deteriorate rapidly, you will not miss the opportunity to close the door.


Fire Attack and the Truck

This piece to this new understanding also involves the front door or the forced, open door used to facilitate the fire attack. This door, like the interior doors, must be controlled and closed as much as possible to limit the amount of air entrained into the fire environment. Now, you may be saying, “You want me to close the front door behind my fire attack crew? There is no way I am going to block their means of egress behind them.” Don’t fret; the Los Angeles City (CA) Fire Department has adopted a policy to have a control firefighter placed at the door. The policy calls for the hand light to be stationed at the opening. This firefighter manages the door and pulls more line to facilitate a clean stretch. Another option that is commercially available which manufacturers are now selling is, essentially, a door curtain that controls the flow path without limiting the ability to safely egress, thus robbing energy from the fire.


 (4) Photo courtesy of Tempest Technology Corporation and John Schafer.

Many “truckies” advocate forcing the door to the fire apartment and holding it closed or controlling it until the line is ready to enter. This practice should be commonplace now. For an apartment or tenement fire, holding the apartment door closed until the line is ready also gives the truck or rescue time to clear the stairs. However, those same truckies (myself included) entering a house would often leave and chock open the door with little regard for timing the engine advance.  Again, these “new” tactics are not necessarily new. We are now putting the pieces of the puzzle together based off our new understanding!

Recommendation 7: If the truck enters the home, you must control the door or hang a curtain to limit energy to the fire.

If the truck is going to locate the fire for the engine, they must manage the flow path in order to maintain safety margins. Remember, if the hose team enters the home and opens the door wide open, it can influence the fire’s growth in the area where the truck is operating. The engine officer is responsible for communicating changes with the truck or the rescue.

The truck can play a pivotal role by closing the door to the fire room. This action will have the biggest impact on the flow path and will stall or reset the fire. We saw this firsthand when filming the ventilation portion of the Tactical Perspective DVD series. We had a room fully involved in fire and venting out of two failed windows. When the truck crew closed a louver door to the room and called for the line the fire stalled, flames turned to smoke, and heat levels dropped rapidly.

(5) A firefighter makes move to close the door to stall and contain the fire.



Recommendation 8: Do not crowd the hall or stairways. Conditions can change rapidly.


Modern Structure Fire Attack

We have all been taught that offensive strategy is fighting fire from within the building and defensive operations are done from outside.  We agree with Daniel Madrzykowski and Steve Kerber that this mentality needs to change! If you are moving in toward the fire, you should be calling this offensive. When you are backing up and moving away, then you are in a defensive position. Why does defensive and offensive attack have to be defined from the location from which water is being flowed?

As aggressive firefighters, we all accept an inherent risk in our professions. However, every day we take steps to make our job safer: We wear seat belts, wear new and improved turnout clothing, and we wear our self-contained breathing apparatus (SCBA) in any toxic environment. Yet, too many firefighters and fire officers continue to fall back on their original training, which was “Get in, get close, and get the wet stuff on the red stuff!”

That may have worked for you in the past and it still may work in the majority of the fires today. However, analyzing the flow path and conditions is a must for all firefighters and officers. Getting in close has very little benefit; all members should use the reach of the stream to increase safe operations. 

Possible energy should be reduced before we put firefighters in the flow path. Many feel this is a new concept, but the Blitz attack has been around for more years then I have been in the fire service, so it’s not all that new! Today, some call it Blitz—hitting it hard from the yard, transitional attack, and many other catchy phrasings. However, whatever you call it, you are still on the offensive as long as you are moving forward.

(6) Fire envelopes the front of a building.


(7) Crews sweep the front of a building with a deck gun to stall the energy while initial handlines are being stretched to the front door to begin an interior attack.


(8) Hitting fire head on.


Recommendation 9: Attacking the fire from the outside is acceptable as long as no crews are already inside and you are moving forward. Note the crew in this photo utilized the reach of the stream to knock down the fire on the eves and then advanced.


Staffing Reality

Firefighters across the country must weigh the risk of operating in the flow path without limiting the energy available to the fire. Some departments cannot stage a firefighter at the door to control the door because they cannot purchase new products to perform this skill. Some departments and some fires don’t allow for water to flow onto the seat of the fire within the time frames stated earlier before the environment becomes untenable. This does not mean we chalk it up as “Well, we do what we can do…. We have done it this way for years, and it has worked.” For the short-staffed fire department, if you are not calling for additional help at a working fire then you are failing to lead and keep your personnel safe.

Recommendation 10: Find a way to take the energy out of the fire. You must attack the fire from the outside before moving in.

Blitz attacks and hitting it hard from the yard is not a defensive operation. Additionally, it is not a tactic where you flow water indiscriminately from the outside until the fire goes out and all the smoke clears. It is simply a 10-second application of water through the window or the door to reset the fire or to take the energy away. This is done so you can safely go in and make a complete extinguishment. Again, this is not a defensive tactic; it is an offensive tactic to keep your firefighters safe.

Departments from cities such as New York; Washington, D.C.; Los Angeles; Detroit; and New Haven, Connecticut, have been hitting the fire from the outside and moving in quickly whenever they are faced with a fire blowing out of the front door. This tactic has proven to be effective and has demonstrated that fire cannot be pushed by water.

In most cities, going around to the back door and pushing the fire out is not an option. You would have to either go through an adjoining building, fake out a dog, break down a fence, or move around cars while the fire is getting bigger. It is also important to size up the fire; not all fires require hitting it from the outside.

Yes, if you stay outside the fire, it will continue to burn in remote locations and in the voids. Thus, you will lose the building and victims. UL and NIST proved this observation through exhausting scientific research. It would behoove you to take the time to read it and view it on line.

See UL’s Firefighter Safety Research Institute Vertical Ventilation and Suppression Online Training HERE.


Water Does Not Push Fire; Air and Ventilation Does

Water that is not moving fire was a surprise to us. We always taught to make a hard push when fire is blowing out the front door; my experience backed up this move. However, I have also been on the inside when a hose stream was placed in a window and made me feel like the sky was falling. The research indicates that placing a line in the window can change the flow path and disrupt the thermal layering. 

Perception can also differ from reality. In the NIST and UL studies featuring FDNY in real occupancies, the heat increase was only measured at a maximum of 10°F. When wearing heat saturated gear and a hood, a 10°F bump feels drastic. The hose stream will also drop visibility and move debris. In addition, the force of the stream can injure a firefighter. With this new knowledge, we now know that a quick outside application of water from a handline will not endanger possible victims. The reduction in energy outweighs any risk from a handline stream.


Recommendation 11: Combining defensive and offensive tactics while crews are inside is still a bad idea and can result in injury.


Playing Water on Smoke

Many of us have been taught, “Never flow water on smoke.” If you haven’t figured this out yet, let us be the first ones to tell you. We were trained based on experience of others and the fire behavior model of a fuel controlled fire. Most fires today require us to take the energy, limiting the chances of the smoke igniting.  When it comes to playing water on smoke, the circumstances will dictate your actions.

Size-up is key if the smoke is not super-heated and endangering your position; applying water will only increase water damage. If the smoke is angry and moving quickly, it may be necessary to reduce the energy by hitting it with water.

Limiting the flow path is critical during all operations. Some of the tactical implications are not “new.” However, some require smart aggressive firefighters to limit the flow path to limit the environment that is too rich to reaching the right oxygen to fuel mixture from lighting off. Keep It Rich!

(9) Smoke is fuel and when heated as seen here requires, hitting the fire, controlling the flow path and playing water on this smoke to reduce energy available to the fire. (Photo by Chris Saraceno.)


Vertical Ventilation

The last piece we must touch on is vertical ventilation. There are some firefighters and officers who have familiarized themselves with the studies. Many have attended classes, read articles and participated in web casts. Some of those fire service members have determined because of what they have read or translated coupled with the fact of lightweight construction today’s firefighters should not ventilate roofs. The authors disagree with this thought process based on research, knowledge and experience. However vertical ventilation cannot be a random skill that is performed at will without communicating with the attack crew. Vertical ventilation still has a place on today’s fireground. However the roof team must perform just like the outside vent team taking the windows. The roof team must not push down the ceiling until the attack line is in place at the main body of fire and or flowing water. With a fire that has penetrated into the attic space the hole can be cut as crews are stretching. However the roof covering should not be pulled until the line is in place and extinguishment has begun.

Today’s fireground must become better choreographed! Firefighter, officers and Chiefs must coordinate and communicate all tactics to keep the members safe!


Special thanks to Steve Kerber, UL Firefighter Safety Research Institute and Battalion Chief FDNY George Healy for their input on this article.

For additional training opportunity to reinforce information contained in this article, the authors recommend you view Fire Engineering’s Webcast sponsored by Tempest Technologies, Tactics & Strategies of Ventilation.


P.J. Norwood is a deputy chief training officer for the East Haven (CT) Fire Department and has served four years with the Connecticut Army National Guard. Noorwood has authored Dispatch, Handling the Mayday (Fire Engineering Books and Videos), co-authored Tactical Perspectives series on Ventilation and MayDay DVDs, and is a key contributor to the Tactical Perspectives DVD Series. Noorwood is a FDIC instructor, Fire Engineering contributor, Fire Engineering University faculty member, co-creator of Fire Engineering’s weekly video blog “The Job,” and hosts a Fire Engineering Blog Talk Radio show. He currently serves on the Underwriters Laboratories Technical Panel for the Study of Residential Attic Fire Mitigation Tactics and Exterior Fire Spread Hazards on Fire Fighter Safety. He has also lectured across the United States as well and overseas. He is certified to the Instructor II, Officer III ,and Paramedic level.

Frank Ricci is a contributing editor and advisory board member for Fire Engineering. He is a lieutenant in New Haven (CT) Fire Department and co-host for the radio show “Politics & Tactics.” He is also a contributing author to the Firefighters Handbook I & II (PennWell, 2008) for the “Safety and Survival” chapter written with Anthony Avillo and John Woron. He was the project manager for emergency training solutions for the Firefighters Handbook I & II slide presentations. He has been a FDIC hot instructor and lecturer. Ricci won a landmark case before the U.S. Supreme Court, testifiying before Congress, and has been a lead consultant for several Yale University studies. He has worked on a heavy rescue unit, covering Bethesda and Chevy Chase, Maryland, and was a “student live in” at station 31 in Rockville, Maryland. Ricci also appears in Fire Engineering’s digital blog “The Job.” Ricci developed the Fire Engineering film “Smoke Showing,” is a co-creator of Fire Engineering’s “Tactical Building Blocks” poster series, and is a part of several “Training Minutes” segments. Ricci has authored several DVDs including “Firefighter Survival Techniques” and Fire Engineering’s “Tactical Perspectives ” series “Command,” “Ventilation,” “Search Mayday,” “Fire Attack,” and Dispatch, Handling the Mayday.” 

Originally ran November 24, 2014.

No posts to display