Battalion Chief Kriss Garcia and Battalion Chief Reinhard Kauffmann answer questions submitted by viewers of their recent Webcast, “Positive Pressure Attack for Ventilation and Firefighting.” You can register and listen to the an archive of this free online presentation HERE. Find out more about their book, Positive Pressure Attack for Ventilation and Firefighting, HERE.
Q. Have you had experience using positive pressure attack (PPA) on balloon construction? Is the fire pushed to the attic?
A. We have done fairly extensive testing of balloon construction buildings and find PPA (with aggressive interior opening of voids and not opening the roof) works fantastic. We conducted a large portion of our tests at acquired buildings used as Army barracks. As we mentioned during the Webcast, opening the roof makes the attic a huge negative space; one in which the buoyancy of the fire, because of the heat travel, will force the fire into the attic area and, in effect, spread the fire throughout the fire building.
With PPA, the interior environment clears so rapidly that crews can see their environment and open all nonfire-stopped voids much more easily than if they had to operate in the smoke. Opening walls and ceilings in balloon construction buildings is difficult; however, if the environment is clear enough for firefighters to work and use saws to get into some of these areas much more quickly than manual tools, once the environment is cleared by the attack, entrance crews can plunge the saw into the floor to the attic for fire involvement before. Thus crews don’t have to get into the building to find the basement entrance.
Q. What is your procedure for operating a PPA fan during winter and heavy snow conditions?
A. We have used PPA during very cold weather (-20 °F-ish) in Gillette, Wyoming. We operate it in this area where we routinely experience temperatures below 0 °F and have found no appreciable difficulty. In fact, the cold air can actually assist to a point, decreasing the interior environment’s temperature quite dramatically. I say to a point because of one instance where apparently the dew point was reached inside the building for a short period of time, turning the interior into a fog bank. The fire was extinguished rapidly and shortly thereafter vision was obscured by a cool, white smoke fog condition. This cleared after a few minutes and caused no problem, especially none that would be permanent or hinder the dramatic benefits of PPA.
Q. What about spreading a fire through an attic space using PPA?
A. We find PPA to be tremendously effective during attic fires. We do not make additional openings in the attic during the attack. If we open the attic, it becomes a huge negative pressure area where fire will travel to and spread horizontally because crews cannot open up large enough holes to let the BTUs generated by today’s fires exit.
Therefore, we bring the fire into the attic but don’t give it anywhere to go or the opportunity to burn the building to the ground. Remember what happens in your fireplace when you open the flue.
Fire of a few decades ago would generate 5,000 BTUs, and back then we trained to start with a 4- x 4-foot hole. Fires of today generate nearly 20,000 BTUs and we still talk about starting with a 4 x 4 hole. The problem with this is if you are working on an old building, you cannot open up a large enough hole fast enough to support interior crews. If you are dealing with a new lightweight building, you don’t have the time. Our tests show the wafer board decking will not support a 200-pound dead load after 3.5 minutes of fire impingement. I will not put crews above an attic fire until I can inspect the roof deck from below and determine if it is safe.
PPA creates a clear environment for crews to operate in as they attack the attic fire from below. We make 4 x 4 openings in the ceiling as we progress through the building, keeping the pressure where we are operating above the attic and therefore decreasing the amount of fire and smoke we get pushing down into the area we are operating. Opening the fewest number of windows on the floor directly under the attic will allow more pressure to remain on the floor while also providing an area where the smoke and fire from the attic that extends into the living area a place to exit, making working conditions inside much safer.
We advocate using power tools whenever possible to help you open any void on the interior. PPA clears the environment so fast that not only can crews operate much more safely, but power tools can operate because they are not starved for oxygen.
Remember the concept of space control. This concept looks at any nonfire-stopped space as one that needs to be controlled with enough water and access to overcome the BTUs. Crews would never think about opening doors to rooms without a hoseline in place to counter the BTUs. Why, then, do we open an attic without enough water or crews deployed to access all of this space with enough water to control it?
Don’t open the attic until the fire has been knocked down from below. This below area will be clean and without heavy smoke conditions so crews can operate much more effectively and safely
Q. I work for a department that uses PPA for ventilation only. They fear using a fan until crews are at the seat of the fire because of fire growth. What is your response?
A. We advocate starting PPA at the very beginning of most fire attacks. If you do not do this, you are turning the environment into one that will not sustain life unless people are dressed just like us. Using PPA at the beginning of the fire while providing enough exhaust makes the fire attack tremendously safe and effective. Not putting crews into areas where they cannot see and where they may be getting into dangerous positions because they cannot see is too dangerous when you consider that anyone inside the building will not survive the thermal balance disruption anyway.
In fact, what you’re talking about is one of the most important precautions we mention in our book. If you have firefighters inside a building and you have not started pressurization, you should remove them and start again from the attack entrance this time with pressurization.
We have heard of instances in which crews had gotten beyond fire because they could not see the area to clear it of fire adequately, then the blowers were turned on, moving the fire to where the firefighters were and injuring them. If you are waiting until knockdown to start ventilation, you are not providing a coordinated attack and you have the time to start again safely because you have already destroyed property with the wet soot and have most likely placed a tremendously toxic environment to where any victims could have potentially survived. Take the time to remove crews to the area of the attack and start the blower this time, clearing the building as they go.
Better yet, start with PPA in a coordinated attack and remove the heat and toxic environment from the building as crews progress, thus decreasing the property damage, and making the space where victims could be located tenable.
Q. Our department has done PPA for years. However, it isn’t a tactical priority at times because of limited staffing. Also, for years we had gas-powered and electric positive pressure ventilation (PPV) fans, but the chief decided to remove the gas-powered fans because of a concern regarding carbon monoxide (CO) in fire buildings. When it comes to using the fans for fire attack, what version of fans do you recommend?
A. Regarding limited staffing, you may be interested in the lasted National Institute for Occupational Safety and Health (NIOSH) report on firefighter injury. Regarding staffing and PPA, let me first say that the fire attack will always go better with a minimum of four members on each engine. That being said and speaking to the reality of staffing in the fire service, many departments do not staff at that level. PPA is dependent upon four jobs being performed to make a coordinated fire attack. This is best accomplished by diving them among four members, but if not, these jobs must be spread out to however many firefighters you have. The four main jobs are:
1. Officer: Sizes up the fire and determines that PPA can be used, making or improving the exhaust opening prior to pressurization. The officer then joins the attack crew as it enter the building.
2. Nozzle: Deploys the attack line to the area as directed by the officer.
3. Blower/Hydrant: If this position does not take a hydrant, this person is responsible for taking forcible entry tools and the blower to the attack entrance.
4. Driver Operator: Operates the pump and assists with hoseline deployment as necessary.
For example, if you tried PPA with three firefighters, the officer would take the blower from the engine on his way to the the building, drop it off near the attack entrance, then continue with the exhaust. The nozzle firefighter would then deploy the hoseline and carry forcible entry tools to the attack entrance. The driver-operator could assist with either of these two functions.
Regardless of the attack, the sequence is covered in much greater detail in our book, but basically the officer ensures there is ample exhaust, then meets the attack crew, at which time the blower is turned into the building. The crew waits for conditions to improve, then makes its entrance.
As for which type of blowers to purchase, we advocate gasoline-powered blowers for PPA. Electric blowers are too slow unless they are deployed at the same time as the attack line without delaying the attack. Also, although electric blowers are improving all the time, they still do not provide the same level of toxic environment removal as gasoline-powered blowers. During a structure fire, the CO level is already more than 1,000 ppm in most interior fires. The blower will reduce this level almost immediately and, during most operations, will continue to operate with a CO level near 100 ppm, which, although not good, is much better than 1,000 ppm. When the fire attack is over, taking the time to deploy electric blowers can be done.
Q. Are you saying that postfire (passive) ventilation is a waste of time?
A. It is not a waste of time, but it does not have the benefits of PPA. If you do pressurization after fire attack, you have already disrupted the thermal balance, dropping the lethal atmosphere and temperatures to the level where victims may be, causing increased property damage, and needlessly placing firefighters in lethal dangerous positions.
Q. What will the activation of a suppression system have on PPA?
A. PPA will make a dramatic improvement in the fire environment. A pressurized attack is very advantageous because, through initial cooling, there is no thermal buoyancy created by the heat of a fire. If the building has a smoke and heat removal system, PPA works well to supplement ventilation.
Q. During the section on postfire PPV, you stated several areas in which this technique did not work. If the fire is out, what does it matter?
A. It’s not that it is an extreme disadvantage, it’s just not nearly as effective. Also, it is dangerous because firefighters are still in explosive and lethal environments and are operating in an environment where, because of the lack of ventilation, they may not be aware of potential hazards.
The exposure of firefighters to what one member of the CDC has called a “soup of carcinogens” is also an extreme disadvantage to our firefighters.
Q. Doesn’t the National Institute of Standards and Technology (NIST) study outline increased temperature spikes because of PPA? You propose general cooling?
A. Thanks for the great question. At five feet and higher, there is an initial increase in temperature. However, our tests indicate that, at the floor level, where victims are located, this is not realized. After the initial increase in temperature, the temperature decreases in a general sense for about several minutes, then starts to rise again. A break-even point of 8-10 minutes is realized until the temperature gets back to the original temperature at which the attack was initiated. For this reason, you must have attack crews ready to advance to the fire area as pressurization is started. Remember, we mention that if conditions are such that firefighters cannot enter, a blower should not be used. It is because of this that we also recommend that firefighters have blowers operating as they are entering, which avoids placing firefighters in a potential heat stream if they place themselves between the fire and the exhaust.
Q. What happen if the fire is in the middle of the structure? Can you still use PPA?
A. There is no disadvantage in using PPA when the fire is in the middle area of a building. The dramatic decrease in temperatures and the increased efficiency of the interior crews allows for very fast fire control. Remember, you need an exhaust at least two to three times the size of the ventilation point or the area where you are pressurizing and making your attack from. For every 18 degrees you decrease the temperature, you decrease the off-gassing of ordinary combustibles 50 percent, making fire extension from one fuel package to another unlikely as long as crews initiate the attack at the time the blower is turned into the building.
Q. Here is is some video from firecamera.com. It shows a PPV fan lighting up a house charged with hot black smoke. What could have been done to prevent this from happening? http://www.firecamera.com/index.cfm?Section=4&PageNum=232
A. Wow! Great video. This illustrates and violates three precautions we go into in our book.
First, start pressurization as the initial attack crew enters. You cannot have crews inside the building and then put a blower up at their back. You cannot account for their whereabouts or the conditions between the blower and the crew and you may cause them much harm.
Second, train and educate yourself regarding PPA prior to starting to implement it. Knowing how to start a blower and not accounting for any of the other conditions will injure or kill firefighters. PPA is a dramatic attack tool that is terrific when used correctly, but is also one that, when used inappropriately, can cause things to get worse.
Third, you need ample exhaust ahead of the firefighters. If smoke and fire come back towards the attack crew, you do not have enough exhaust and have not controlled the environment by directing away from your crews; you are just going through the motions. Adjust and continue the attack only when you can see and clear the building of fire as you advance towards the seat of the fire.
Q. The majority of structures where I live have most, if not all, their windows open because our warm climate. How will this affect the outcome of PPA if you have numerous exit points in the structure?
A. I don’t believe this is a problem. We have done our class in the Florida area and other places where windows are generally open and have found no real issue. The reason for this is the fire creates a tremendous amount of the pressure, with water application once again creating even more. With your windows open, the fire will most likely be venting from the leeward side of the structure, making the attack at the windward side very obvious. Thus, during the initial fire attack, which we are focusing on, there is plenty of pressure in the structure. The blower simply increases the pressure that is already there, no matter what that is. The blower will increase the interior pressure approximately less than one tenth of a percent, but that is in addition to what is already there, regardless of your starting point. This increase is enough to ensure that the fire will continue to vent to the largest negative pressure area ahead of attack crews while they rapidly advance to the seat of the fire.
After the fire is out and you lose the majority of your pressure, the open windows may make it more difficult to remove the remaining nuisance smoke, but at that point you have all the time in the world to open and close windows and doors to assist with this operation. Taking additional blowers inside the structure and placing them at interior partitions, much like we do on the exterior at our initial attack entrance, will also assist in removing smoke from an area if the building has too many openings once the fire is out.
Q. You stated that fire spread is decreased by the use of PPA. But if you make an exhaust opening not in the fire room, you will probably spread the fire to that room. What is your response?
A. In our classes over the past 10 years, we have demonstrated that this does not happen in dozens–if not hundreds–of live burn scenarios. We call this demonstration a “pull.” During this scenario we light a fuel package in one room on fire, place other fuel packages adjacent to the fire leading toward a different room up to and at the exhaust, which is located in the adjacent room. The fire is ignited, and when the closest fuel packages start to smolder, we open the exhaust in a different room, in effect trying to spread or pull the fire from the original room to the room where the exhaust is. We have never been able to pull the fire from one room into an adjacent room where the exhaust is located.
The reason for this is the rapid decrease in temperature within the fire building. For every 18 ° F the temperature of an ordinary combustible is decreased, the off-gassing or pyrolitic decomposition of the material decreases 50 percent. Although not exactly correct, one could infer that the ability of ordinary combustibles to burn is decreased 50 percent for every 18 ° F decrease in temperature. While observing this from inside, we watch the fire or flame exit the room on the way toward the other room where the exhaust is made, but the fire never even bends toward to the exhaust made in an adjacent room.
Q. Does FDIC ever have live fire training with these methods? What can we do to help the officers in our department embrace PPA?
A. We have presented at FDIC several times, but have never been able to do a live burn there. We would love to do a hands-on class there. Feel free to contact FDIC and ask for more hands-on PPA training. At FDIC 2008, we will present a class called “Positive-Pressure Attack: Achieving the Coordinated Fire Attack.”
Q. Is the research paper that was done by the firefighter from England that Reinhard mentioned in the opening session available?
A. The url for the site is http://www.firetactics.com/PPV-YATES.pdf.
Q. How can positive pressure be accomplished with exit two to three times larger than entry opening? Positive pressure is only created with smaller opening at exit.
A. PPA is less about positive pressure than it is about ensuring the fire has a negative area to exhaust and maintaining this exhaust in front of the advancing fire attack crews. Generally speaking, the blower only increases the interior pressure as measured with pressure transducers less than 0.1 percent. The fire needs a safe exhaust to allow the pressure created by the fire (and also by water application) to evacuate from the area. The crew needs an increase in pressure just a fraction higher than the area outside the structure to ensure that the lethal products of combustion are exhausted ahead of them.
What you are talking about is one of our most serious precautions, which concerns not having an adequate exhaust. If you do not have ample adequate exhaust (at least two to three times the size of the entrance) you are in effect turning the building into a convection oven, which can cause the fire to grow exponentially.
If you are talking about the nuisance smoke left in a structure after the fire is out, we have all day for this to clear. If this is our goal, we can then take blowers inside the structure and open and close doors to various areas to increase the pressure or blow this nonlethal environment out of the building. In our estimation, at that point this is no longer an emergency. We could leave and come back several hours later and things would be better even without our intervention.
Q. Are you familiar with the studies done by Larry Hughes in North Carolina and the CO levels?
A. I am aware of some of Larry’s early tests. Our views on CO are this: During a structure fire, there is already well over 1,200 ppm of CO present. The blower will decrease this, as well as dramatically reduce the level of other lethal products, including hydrogen cyanide, benzene, and temperatures above 250 degrees. PPA will take that initial 1,200 ppm and reduce it to less than 100 ppm. Remember, you will be in SCBA, so this is not a problem. Victims can survive the 100 ppm for well over an hour, whereas less than a minute of exposure to 1,200 ppm will be fatal.
Q. Does Vent Entry Search (VES) mean that a firefighter is going into the vent opening to search?
A. Yes, tactically some departments embrace VES as a means of searching rooms while entering windows from the outside. This is done in coordination with the fire attack. If this tactic is used, we cannot be sure that one of these windows will not become an exhaust because we don’t know where the interior crew is or how effective they have been in completely controlling the fire. Any window could become an exhaust. This is one of our precautions for when not to do PPA.
Q. When knocking out windows, do you want to take out all the windows or be selective?
A. This is the sequence of taking out windows.
First, take out a window in the area that you assume to be closest to the fire. Most of the time fire will be showing, so this is not a big deal. However, if it is not obvious, take your best guess and see if that window starts to exhaust a heavy volume of smoke and fire. If it does not, take your next best guess. If you still do not get heavy products of combustion and there is a sublevel, open one of those windows to make sure you are not entering an area that may be unsafe. If you still do not get a heavy volume exhausting, check the floor above on your way to the attic area. A thermal imaging camera may be of some help if one is handy and will not delay the attack. If any of the windows mentioned above yield a heavy volume of fire and smoke, open adjacent windows on each side of that one with the idea being that you are clearing additional rooms.
As always, the exhaust should start at two to three times the size of the entrance, and then be adjusted based upon fire conditions. If fire and smoke are still exhausting with high levels of pressure, you could still use additional openings. If fire and smoke are returning to the attack entrance and trying to exhaust over the top of the blower, you could still use more exhaust openings. If the interior environment is clearing and crews are making continual progress throughout the structure, your exhaust is adequate.
If crews are not making continual progress and fire conditions are not allowing them to advance for more than five minutes, give strong consideration to evacuating the building until conditions can be improved wither with additional crews or better ventilation.
Q. Our initial attack is a pumper, an attack pumper, and a rescue, with a total of three men–one man per truck. It’s not a lot, but that is what we got. With only three men (until help arrives), we are going to have to delay some function in order to get a fan in place. After listening to your presentation, I believe getting a fan in place is of utmost importance, but in what cases (if any) would you advance a hoseline quicker instead of taking the time with a fan? If you have a room-and-contents fire with someone yelling for help, would you position a fan then get a hoseline, or go for it with just a classic hoseline attack?
A. The easy answer is: if I can supply the fire with ample exhaust and then place the blower to remove massive amounts of the products of combustion, my hoselines can be much more effective when they advance. If you only have a few members on-scene to make entry, they should do so in the best environment they can so they can see and operate aggressively as they make there way to the fire and victims.
Regarding the victims, if they are at a window that could become an exhaust, yes, get them first. If they are anywhere else in the structure, especially on the floor, conditions will dramatically improve for them if PPA is used. We have heard of a couple of instances where victims have even self-rescued before firefighters could get to them once the environment cleared to the point they could make their way out of the building.
Regarding the time portion of your question, as any member makes his way to the fire building, he can take a blower with them if it equipped with a handle and wheels. The two things you need for an effective fire attack is a hoseline and ventilation. Take both with you. I know of some small departments that routinely operate with three members and, although not right, they do so in an effective manner because they deploy ventilation with the hoseline. Take the time. A few more seconds at the beginning of an incident make the attack much more effective and efficient are well worth it.
Q. I find your book very informative, but please clear something up for me. On page 86 it says: “PPV raises the pressure of the interior atmosphere only slightly-just 0.1 to 0.2 psi.” Page 124 says: “The amount of pressurization created by the fire is approximately 0.5 psi, or about 25 percent of the pressure created by a blower.” Please clear up this apparent contradiction.
A. The comment demonstrates that the book was read very, very carefully, and the questions are good ones. However, the numbers on page 86 do not have a direct relationship with the numbers on page 124. Each statement relates to different aspects of positive pressure.
The figures “.1 to .2 psi” on page 86 (Chapter 4, Understanding Positive Pressure Ventilation), relate to the additional pressure a blower creates in the interior of a building. This figure is not from the authors, but based on laboratory tests by Air Movement Control Association (AMCA) in a controlled environment.
The comment on page 124 (Chapter 5, PPV + Initial Fire Attack = PPA = Coordinated Attack) refers to increases in air pressure, or velocity, at the exhaust opening. As stated in several places in the text, there is very little air velocity inside a pressurized building except at the ventilation opening and the exhaust opening. This rough figure is based on tests conducted by the authors as explained in later sentences in this same paragraph. (See Figure 8-1 on page 208 for an idea of how this was measured.) This is demonstrated as the interior environment is forced out of an exhaust opening where the increase in velocity as measured in pressure demonstrates the authors’ point of a dramatic increase in exhausting pressures.
To address the specific questions at the end of the reader’s message: “Since the pressure created by the blower is 20 percent of the pressure generated by a confined fire, does PPA really work as intended?” As explained above, this figure of 20 percent is not accurate because the two numbers in the text relate to different things. The slight increase in interior pressure created by blowers is enough to make PPA work very, very well.
“The fire will be exhausted out the exhaust opening no matter whether PPA is used or not.” This is true, although it will not exhaust nearly as effectively or controllably as with positive pressure.
“In reality is it true that PPA gives ‘only slightly’ (p. 86) an extra push to the ventilation process?” This is true, but, as stated above, only this slight increase in pressure creates ventilation that quickly has an extremely “positive” impact on the interior environment.
Again, the comments are much appreciated and point out an important way this text can be clarified. Please express our sincere appreciation to the person submitting the questions, and thank you again for passing them along.
Q. Fans can’t make pressures of 0.1 psi, more like 0.01 psi.
A. Thanks for keeping us straight. Depending on where the pressure transducer is located, small variations of psi are expected. It is more the difference in pressure we are talking about, not the pressure that could be maintained in an open vessel such as a house.
During a group of our evaluations at AMCA, we had an increase of interior pressure near one tenth of a percent (0.1 percent). That is where we obtained this information. No doubt depending on the domain, as well as other variables applied by the team that is doing the modeling, the results could be varied.
More importantly, the low increase in psi that we reference is to demonstrate the relative small amount of psi the blower causes in direct relationship to the increase in pressure that the fire and then again the water application creates.
Whether it’s one tenth or one hundredth, the amount is small, yet more than enough when you assume the psi inside near the fire may be hundreds of times the pressure outside the structure where we are trying to get the products of combustion to go. It’s not the amount of pressure we are working with, it’s the difference.
Q. In balloon construction, is it wise to immediately create an interior access to attic area to pressurize attack in an effort to prevent extension?
A. Our experience using PPA in balloon construction demonstrates that you can open interior voids, including the attic space, to inspect for hidden fire. In fact, we instruct our firefighters to inspect the attic within the first few feet after making entry if there is no indication that the fire is on the main floor or basement area. This prevents them going deep into the interior with active fire overhead.
The big error in fighting fire in balloon construction is when the roof is opened, in effect creating a chimney for fire spread. If you are using PPA, go ahead and inspect the attic area, but if you open the roof, the fire will quickly spread from the voids and involve the attic area.
Q. How is it that victims would be in less danger if they were in between the fire and exit?
A. I believe you are referring to our statement that victims that are on the floor between the fire and what will become the exhaust opening have a greater chance of survival using a positive pressure attack over other ventilation tactics. This has been confirmed by tests that demonstrate the decrease in temperature and introduction of clean, cool air into that area where the victim is located, leaving them in a much improved environment and providing increased visibility for rescuers to see the victim.
Q. How do you account for the “two-in/two-out” standards now being used in fire suppression? Are you waiting to advance into the structure until additional help arrives? Have you tested the fans in a wind-driven fire, such as a high-rise with window failure in the fire apartment?
A. The two-in/two-out standard allows for entry in situations in which a known or perceived rescue situation is present. Our officers make that decision based on dispatch information and scene size-up. If this is the case, the first arriving engine crew will make a positive pressure attack without the second arriving unit being on-scene.
We have done several test burns in wind conditions that ranged from moderate (say 10-20 miles per hour (mph)) to high wind situations above 20 mph. In residential structures, we have experienced significant exhausting of the products of combustion in wind conditions up to 20 mph, however one cannot overpower Mother Nature in high-wind or gusty situations. Our advice has always been to make entry, if possible, from the windward side and allow the wind to aid in the attack. We have done live burns in two- and three-story fire department burn buildings that also demonstrated smoke exhaustion against the 10-20 mph wind. If you recall we showed in the Webcast a photo of this particular test with the windsock blowing one direction and smoke exhausting toward the wind. Again, experience and respect for the power of wind must be taken into consideration during the initial size-up.
Q. We have a problem with hurricane windows. Do you know anything about how these windows react in a fire?
A. Good question, although we are more familiar with blizzard windows here. We have never encountered or tested hurricane windows. I can only generalize and answer that in order to use PPA you must have an exhaust opening as well as the ventilation opening (where the blower is positioned and crews enter). If your only exhaust opening has a hurricane window and you cannot open it, PPA is not going to be your best ventilation tactic. However, if you can open a nearby door or other opening, it may still be an option. We have used windows and doors in the adjoining room to the fire as the exhaust opening with good ventilation results. A common thought is that doing so will spread the fire to that next room, but our tests have shown that not to be the case. In fact, because of the cooling effect that PPA produces, the fire is less likely to grow in size and will not spread easily. When we teach fire departments PPA, we will intentionally open an exhaust in the next room to demonstrate this under live fire conditions and have yet to spread fire.
Q. How does it work in sublevels? Are there any special precautions when using PPA in a basement fire?
A. We have tested PPA under live fire conditions and fought actual basement fires using PPA with excellent results. The key to sublevel or basement fires is being able to open an adequate exhaust opening. In Salt Lake City, most residential structures have a basement with smaller window openings than the upper levels. We instruct students to open the window nearest the fire and then augment that by opening additional windows at the basement level. Having an adequate exhaust is key to getting the heat and products of combustion out the sublevel. The other element to consider is blower positioning. An outside opening to the sublevel would be the first blower position, with an additional blower placed at the stairway leading down to the sublevel.
Q. Is PPA still a viable tactic if a lot of windows are out of the building?
A. In general, the answer is yes. Having adequate exhaust opening (s) is key to PPA. It depends on what you specifically mean by a lot of windows. When we instruct firefighters in PPA, we teach them to be aware of the existing conditions. For example, if smoke and heat are blowing out from the ventilation opening (where the blower is positioned and crews are entering), this often indicates that the exhaust opening is not adequate and another exhaust opening should be made. In terms of your question, check out the exhaust of the smoke. If you notice a significant increase in the amount leaving the structure, your PPA is operating. Also, check with the interior crews, they should be noticing a significant improvement in terms of heat reduction and increased visibility.
Were all of your fire attacks done with fog nozzles ,or did you do any attacks with smooth bore nozzles? Was there any difference with the results?
A. Our test burns and live fire classes have mostly been done with fog nozzles. Because PPA allows firefighters to quickly find the seat of the fire, we have had good results with using fog nozzles set to a straight stream.
Q. Have there been complaints from fire investigators when this tactic is used?
A. That is an interesting question. Our department has three full time arson investigators, and we have not had any negative comments from them. PPA allows for a rapid fire attack while also reducing property damage, therefore our assumption is that it aids investigators in their search for the fire cause. We have asked the investigators to conduct research on this topic and hope to include their findings in the second edition of our book.
Q. Why are departments reluctant to examine this technique?
A. That’s a difficult question to answer, since every individual department probably has its own opinion of PPV/PPA. I can say that there are three common elements which we have noted over the years that we have been teaching: tradition, mythology, and education.
Fire service tradition is deeply entrenched. Most traditions are good, but some could probably use some retooling. Many traditional departments are dead set on truck companies opening roofs and, in some, that is their forte. Our response to this is that we would rather see truck companies doing forcible entry, search and rescue, overhaul, and so forth. Because PPA allows the first-due engine to begin a coordinated attack, truck crews can immediately begin a search and rescue operation to save victims.
The mythology part is the one that continues to spread those well-known stories of blowers spreading fire, blowers being responsible for firefighter injury or deaths, and blowers behaving in unpredictable ways. Unless departments actually experiment and test PPA, the mythological, untrue stories will continue to be told and propagated within the fire service culture.
This leads us the third element, education, or more accurately, the lack of education and understanding of the principles and theory of PPA. Unless fire departments undertake a serious study of PPA and pass it on to their firefighters, resistance will continue to be an obstacle. When we instruct, our objective is educate and train firefighters on an equal basis. It is fortunate and gratifying to see that NIST has taken a very proactive study of PPV/PPA, which will go a long way in educating firefighters.
Q. Not a question really, but it’s not about pressure, it’s about pressure differences!
A. Yes, you are correct. We are probably all saying the same thing, only differently. The pressure differential is widened by the blower along with the natural increase of pressure due to heat and the compression of gases in an unventilated structure, increasing the pressure inside the structure, thereby causing movement of the interior air to an area of less pressure outside of the structure.
Q. What about the “jet stream” created by PPA (scientifically proven) and building geometry?
A. Heat and products of combustion will move toward an area of less pressure. The careful selection of the exhaust opening will determine the direction or location that it will move to. By the term “building geometry,” I assume you mean the interior layout of the fire structure. In order for PPA to be most effective, an adequate exhaust opening must already be present or made by firefighters. Obstructions in the interior such a closed door to the involved room or area need to be addressed. Smoke that has spread to other areas of the structure can be exhausted through another exhaust opening made elsewhere besides the involved room. Often, interior crews will first have to determine the location of the fire and subsequently open a door or other obstruction to the involved room. Again, prior to this an exhaust opening must be present in order to avoid a dangerous situation to interior crews. Good communication and incident command are key in situations such as this. In cases where the involved room is accessible (no closed doors or obstructions) but the exhaust opening is made at an adjacent room, the air movement will be toward that exhaust opening. Our experience has shown that although heat and smoke move toward the other room, the fire does not spread. We attribute this to the cooling effect of fresh air being introduced that in effect decreases the chemical reaction of combustion.
Q. In the beginning of the Webcast, you gave a statistic on the percentage of “saves” when PPV is used first versus fire attack. Could you review that again in a little more detail?
A. The point we are making was that PPA allows the first arriving crew to begin a coordinated fire attack, which to us means that ventilation is not just in progress but actually operating at the same time that water is applied to the fire. This prevents the thermal layer from lowering down to the survivable space where a majority of the victims are found. It also decreases the severity of burns and the time that it takes to cause those burns. The opposite will be the case if crews begin fighting fire prior to ventilation being operable. The thermal balance will be disrupted and heat, smoke, and steam will invariably bank down and make life miserable for everyone. Therefore, more survivable victims may be found in a timely manner by using PPA, rather than attacking the fire prior to any ventilation being operable. The key is that fire attack must be coordinated with ventilation. You just can’t have ventilation being worked on during fire attack–it must be in operation for the maximum benefit. Our informal survey of past firefighter students has shown that most survivable victims are recovered from involved fire structures prior to the application of water.
Q. Do you believe in sealing the entrance point, or is just blowing in it and entraining air good enough?
A. The short answer is that we don’t emphasize feeling around the door to ensure that there is an adequate air seal. The newer generation of blowers produces a high output of cubic feet/minute and have the ability to tilt. This makes for a more efficient blower that will deliver a sufficient amount of air for an adequate ventilation operation. Our experience has also made us aware that not every ventilation point will be the perfect one in which the correct distance between the blower and opening can be achieved. Porches, stairs, and other building impediments require that firefighters place blowers for their maximum benefit, although not in a textbook-perfect location.
Q. Have there been any reported firefighter death because of PPA?
A. I want to be very specific in this answer. We are not aware of any firefighter death in conjunction with the appropriate and correct deployment of PPA. When we teach firefighters PPA, they are made aware of the correct application and the precautions that must be understood and strictly adhered to.
There are NIOSH reports of firefighter deaths that, among other elements, have the use of a blower as part of the overall operation. A careful study of these reports reveals a multitude of conditions that came together and resulted in a catastrophic event. I have included the link to one of these NIOSH reports below. Please pay close attention to the NIOSH recommendations to prevent a recurrence of a similar event. We can’t possibly point out all of the material that is in our book in this brief article, but like all other fireground operations, you must be aware of the precautions and limitations of any particular tactic. Firefighters should never enter a structure prior to an exhaust opening being established or present, blowers should not be put into operation after firefighters have already entered, and incident command should always be aware of interior conditions and make adjustments accordingly.
Q. How do I register for the train-the-trainer session in March 2008?
Thanks for your interest in the course. We are in the planning stage and will be announcing details on our Web site: www.positivepressureattack.com
Kriss Garcia, who has served in the fire service for 25 years, is a battalion chief with the Salt Lake City (UT) Fire Department and chief of the Tooele City (UT) Volunteer Fire Department. He has a bachelor’s degree in public administration, is a licensed engineering contractor and a paramedic, and is an NFA Instructor. He serves on the NFPA 1021 committee and is a voting member of the Air Movement Control Association. His interest in positive-pressure ventilation and positive-pressure attack began in 1989.
Reinhard Kauffmann is a battalion chief for the Salt Lake City (UT) Fire Department, where he has served for 30 years. During his career, he has held the positions of paramedic, interim chief, and airport fire chief. He has a bachelor’s degree in microbiology and has been extensively involved with positive pressure for firefighting since 1989.