Keeping a fire confined to its room, floor, building or neighborhood of origin is a critical objective of every incident commander. Anticipating how a fire can spread from one area to another has always been a challenge for the members of the fire service.
Our difficulty, most notably comes from the lack of personnel on the fire scene to check and protect all the avenues of fire spread. But as that battle continues, fire service educators must continue to identify and discuss how fire will move within and beyond the structure.
INTERIOR EXPOSURES
Exposures are often categorized into two reference areas: interior and exterior exposures. Interior exposures are those areas that surround the fire area or fire floor. They are identified from the avenue and direction of fire travel from within the building. Direction of fire travel is referenced from the fire’s ability to move vertically up through the building, horizontally left or right from the point of origin, as well as any areas below where the fire may be able to drop down.
It is from this simple geometric thought that we gather the association that all fires have six sides, and depending on the possible avenues of fire travel within a building, all six sides must be examined for potential extension. But as easy as that sounds, we need to be more detailed regarding the possibilities and further identify what actions we can take to check and protect.
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The location of the fire
We often refer to this as one of the most influencing size-up factors in our decision-making. Knowing that the life hazard is the most important, where the fire is and where it can extend, has continually been one of the most influencing factors. Because of this reference, we need to clarify the concerns. Let’s continue.
2
The floor
Generally speaking, lower-floor fires present a more immediate challenge for fire forces simply from the fact that more of the building and its occupants are exposed to the fire from below.
3
Interior stairs
In a multi-story building, the interior stairs will be the largest unenclosed vertical opening in the building. If we quickly go back and reference the floor location, we are continually reminded of why incident commanders always direct one of their first hoselines to protect the building’s interior stairs.
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Room/occupancy type
When interior crews report that they have a fire in a kitchen or a bathroom, our experience and education reminds us of the concerns that fire extends beyond the room and contents and into the utility voids found within those rooms. If we present more specific information and inform you that you are going to work at a fire in a multiple dwelling, our concern extends to the challenges of stacked kitchens and baths.
If I change the occupancy and tell you that your fire is now in the kitchen or bathroom of a garden apartment, we would need to modify the concern to now reflect the challenges of not only stacked, but also back-to-back kitchens and baths.
Let’s go one step further. Anyone who has operated at a fire in a large frame dwelling, often called a “Queen Anne” or a “Victorian,” will tell stories about how difficult and challenging fires in these types of buildings are. The specific challenges often focus around when a fire in one of these buildings has originated or extended into a concealed space. The void spaces in Queen Anne or Victorian structures are extremely large. Their ability to hide fire, spread fire and produce explosive, often overwhelming fire growth, is well known. If there was ever one type of building where you need disciplined coordination of your ventilation, a number of hoselines in the building, numerous means of egress and a true understanding of what can happen when you introduce air into a concealed space, it is here.
Fires in concealed spaces and voids present numerous challenges, but when they involve the size and number of void spaces that these buildings possess, unsuspecting members will get hurt. These are some of the nastiest structure fires you will ever fight. The last thing you want to do when opening up is make the fire angrier than it already is. When discussing structure fires, the late Frank Brannigan would often say you need to “know the enemy!” He was referring to the building and how it behaves when being attacked by fire. A quote that many of us refer to each day; but consider adding the above to your list.
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Balloon framing
Homes that are of a balloon-frame design will let a fire in any unfinished basement move vertically up throughout the building because of the lack of fire-stopping in the building’s exterior walls. Tactics often referred to with this type of fast-spreading fire focus on the quickness and mobility of the initial hoselines on the inside of the structure at the exterior walls and at the fire’s ultimate collection point, the attic.
We have all struggled with the removal of the wall area on the first floor of these occupancies in an attempt to direct water up the stud channels to slow the fire’s spread up. Add a number of small rooms cluttered with furniture, and the delay of opening up the walls to get a stream of water directed within the space is extended even further.
Alternate tactical options do exist if members can access the structure’s exterior sides. If the balloon-frame private dwelling you are operating in is not attached or close to other structures, take advantage of the accessibility to the structure’s exterior. Assign a ladder company to remove some of the structure’s exterior siding/sheathing at the first-floor area in any wall space that does not have an inherent fire stop (windows, doors and diagonal bracing are inherent fire stops within a balloon-frame design building).
Having the ability to remove vital areas of the building’s exterior skin in a clear, uncultured atmosphere allows a hoseline quicker and easier access to the void spaces all in an attempt to slow the fire’s vertical spread. It must be noted, as successful as this tactic has been for many in the past, its use must be disciplined to ensure that it does not drive fire onto firefighters operating on the inside of the building. Coordination and communication are critical requirements.
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Floor- and roof-support systems
Buildings constructed with trusses, wooden I-beams and cold form steel are what I refer to as “lightweight”-designed buildings. Over the years, the fire education community has identified and discussed the inherent flaws and collapse dangers of these systems. But a design flaw that not only enhances the collapse concerns, but also promotes uninterrupted fire spread throughout the structure is the open web design associated with the truss support systems.
Let’s consider the following. In older, stick-built structures we are used to floor and roof supports systems of two-by-eight-inch or two-by-10-inch joist/rafter designs and the strength they provide. But their design within the floor plan also helped slow the fire spread. Think about it. If a fire extends from the buildings contents into the floor structure, the fire “initially” can only move 10 inches high, 16 inches wide and spread through the floor bay from bearing wall to bearing wall. A concern, yes, but when your floor and/or roof system is built of a web design, as it is with a truss system, the fire literally can and will spread quickly throughout the entire “footprint” of the building! A tremendous concern. The dimensions of the building will actually identify the unobstructed space and the fire’s ability to spread. Now add the collapse concerns, and the challenges become compounded.
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Basements, cellars and attics
With many basements, cellars and attics in private and multiple dwellings having unfinished ceilings, we generally consider a fire in basement, cellar or attic to be a “structure” fire, not a “content” fire. Without over analyzing this, a fire in this area will immediately expose and quickly involve the structural members when the ceilings or support members are unfinished and not protected. If we have additional information that indicates the floor or roof system is made of “lightweight” building materials, collapse has to be anticipated.
Control within
As fire service educators continually review and discuss fire spread within the structure’s voids, we also need to remind ourselves of how and why a fire can quickly move from room to room, and floor to floor through the common areas. Over the years, we have seen a dramatic increase in the heat release of the building’s contents. This is most notably due to the increased use of plastics and synthetics in the home, but also from the increased R-Values in the walls and ceilings and energy-efficient windows, as well as the overall amount of building contents. The end result from the above is hotter fires, quicker time lines to flashover, an increased frequency of backdrafts in the field all resulting in an increase in firefighter injuries and deaths.
What can make matters worse is the how the fire department operates at a building fire. Recently, the National Institute of Standards and Technology (NIST), Underwriters Laboratories (UL) and the FDNY released an extensive study reviewing fire behavior in modern buildings with modern furnishings. One of the many points of the study focused on how a fire department ventilates a fire building, how we must take a more disciplined approach to where and when we ventilate fire buildings in direct relation to the use of water in a modern building. A condensed review of the findings is asking us to revisit some old tactics as well as add a few new ones.
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Controlling flow paths and fire growth
Our education and experience over the years has repeatedly told us that any time we ventilate a fire building through any opening, it must be coordinated with the engine company’s movement. This concept is not new, but what is new is how modern furnishings in a super-heated environment can present overwhelming fire growth, most notably when an opening or removal of a window, door, or roof opening is not controlled or coordinated, and how that opening affects the fire’s “flow path.”
Flow path is defined as the movement of heat and smoke from the higher pressure in the fire area/fire building toward the lower pressure in the structure through such avenues as doors, hallways, stairs and any open or removed windows, skylights, scuttles or roof-cutting operations. More than ever before, fire departments are being reminded to take a more disciplined approach to where, when and how they vent. This awareness is being combined with a stronger emphasis on getting water on the fire and quickly cooling the environment, staying out of anticipated flow paths, controlling flow paths, the use of thermal imaging, assessing wind speed and direction and where possible giving consideration to room, hallway and floor layouts prior to venting. Taking all of this into consideration and communicating to interior members the where and when of the vent is a must. Much needs to be done and discussed as we move forward on this subject.
Next: Exterior exposures
