By PJ Norwood – originally posted at: http://www.fireengineering.com/articles/2015/09/vertical-ventilation-should-it-still-be-a-primary-tactical-assignment.html
In 2013, Underwriters Laboratories-Fire Safety Research Institute released the report Effectiveness of Fire Service Vertical Ventilation and Suppression Tactics in Single Family Homes. Since that time, there has been some heated fire service debates on the when, how, why, and if we should still be performing vertical ventilation. All of the debates (when kept positive) are healthy for the fire service. When we are debating, we are asking questions, discussing our tactics, considering other options, and evaluating the what, how, and why we do what we do on the fireground.
Unfortunately, whenever something is introduced that is different from how we normally operate, there will be some that feel threatened and reluctant to change. Instead of embracing change, they are reluctant because of the “it’s what we do, and it works” mentality. This mentality is vastly different from how we handle emergency medical services (EMS) within the fire service. Every year, we see changes in our delivery of patient care, and we embrace these changes. This is something that I will never understand, and I do not want to focus on it today.
So, should vertical ventilation still be a primary tactical assignment? There are no absolutes to what we do on the firegound. When it comes to vertical ventilation, my answer would be, “It depends.” There is no silver bullet. The rule of thumb for vertical ventilation was always this: Open the roof anytime there is fire on the top floor or immediately under the roof. Although there is absolutely still a place for vertical ventilation, and everyone will always say it must be coordinated (though online and social media video posts) it makes it appear that we are not applying the coordinated piece to the fireground. Granted, coordinating the hole and water application can be very challenging, but if you are going to cut a hole, it must be coordinated.
Although we know that when we open up, we will get some “lift” and “relief.” What we do not understand is that the “relief” aspect will only be temporary. If you open the roof and do not apply water or put yourself in a position to immediately apply water, you’re doing it wrong, and you risk taking that “relief” and creating a worse scenario for your interior crews.
Photo by Robert Ladd.
Depending on the size of the structure and the size and amount of other openings creating flow paths, interior contents and interior sheathings will directly affect how much or how little time you have, from the time it’s opened to the time of flashover. Remember, when the room flashes, it’s not tenable! So, if you perform vertical ventilation and do not immediately apply water, you run the risk of creating a flashover of the occupied space in which your firefighters are operating. The “lift” and “relief” will quickly turn to firefighters bailing out of the building! (The above example is primarily for a top-floor fire involving the contents and structure, not the attic space.)
Let’s consider fires that involve the space immediately under the roof—the attic space. Some will say that, for any fire immediately under the roof sheathing, you must open the roof immediately. However, those who truly understand today’s fireground know that this is not an accurate statement. Should you still open the roof? Yes, if you need to remove the smoke and heat, but not until after you apply water. When you open the roof, you are releasing the smoke, heat, and unburned products of combustion. When you release these items, you are replacing them with fresh air.
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We all know that as we increase the fresh air into the structure, the fire will increase in size. The term we hear too often (and it’s used positively) is, “We know the hole worked because it lit off.” This much is obvious; when you open up the roof and provide the ideal mixture of heat, fuel, and air, it will light off. However, this is not a positive event for the fireground. It may look good to the fire buffs and photographers standing in the street, but it’s not good for the building and firefighters operating within. If the smoke or gases have turned to flames, it’s because the ignition temperature of those gases has been met, and we now have flames, which creates a bigger problem because of fire spread.
For an attic fire, keep the roof “tight,” i.e., do not create a hole until you have applied water and temperatures have been reduced in the attic space. Remember, more heat equals more water is needed for extinguishment. Greater water means greater damage to the contents. Remember property conservation? If you are creating an environment where more water is needed to extinguish the fire, you are damaging property, not saving it. Additionally, if you are causing smoke and gases to light off, you are also increasing the fire damage to the building.
Photo courtesy of Underwriters Laboratories-Fire Safety Research Institute.
Keep attic fires vent limited; apply water through the eaves or the smallest hole possible on the interior before you open the roof. You should open the roof only after extinguishment and IF it is still necessary to open it. I also believe that, after extinguishment, it is not necessary—in most situations—to open the roof. If the fire is extinguished, why open the roof? Are there other ways to release the smoke and heat? Might it take a little longer to evacuate the smoke and heat? Yes, but is it better to hold off and have some patience then unnecessarily cut a hole in someone’s roof?
A few things to remember:
- Smoke is preheated fuel just waiting for you to make a mistake. It is a mistake to open up and create an ideal mixture of fuel, heat, and oxygen without applying water.
- The primary goal prior to opening the roof is to emphasize getting water on the seat of the fire and controlling the building’s openings.
- “Once ventilation takes place, conditions change rapidly.”
o Fire growth and spread are greatly determined by ventilation.
o Although there are many factors that influence the time of ventilation to untenable conditions. There are documented times for which you must be prepared, examples of which follow:
– One-story residential structure = 1 minute, 40 seconds.
– Two-story residential structure = 3 minutes, 20 seconds.
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. He has authored Dispatch, Handling the Mayday (Fire Engineering, 2012); coauthored Tactical Perspectives of Ventilation and Mayday DVDs (2011, 2012); and was a key contributor to the Tactical Perspectives DVD series. He is a Fire Engineering University faculty member, co-creator of Fire Engineering’s weekly video blog “The Job,” and host of a Fire Engineering Blog Talk Radio show. He is certified to the instructor II, officer III, and paramedic levels.