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Tactical Consideration: Building Construction Affects Fire Behavior

Previous research conducted by UL has shown
that the increased use of plastics in residential homes has resulted in fires which are more
likely to become ventilation limited prior to fire department arrival. This emphasizes the importance of fire department
ventilation tactics. Realistic live fire training is an important
tool to help firefighters understand how fires react to ventilation tactics. However, some buildings may make teaching
ventilation limited fires challenging. Concrete live fire training buildings in particular
often have many building features, such as metal doors and windows and scupper holes,
which a residential structure would not have. While these construction features aid with
cleanup and ease of use of the concrete building during training evolutions, the leakage air
in the structure affects the fire dynamics. Consider the differences between the concrete
live fire training building and the ranch house used in the horizontal, vertical, and
positive pressure ventilation projects. Although the footprint of the ranch house
is larger than that of the concrete building, the volume of the second floor of the concrete
building alone is nearly twice the volume of the ranch structure. The leakage in the concrete building is also
several times higher than the leakage area of the ranch structure. Consider the difference in fire behavior between
a furnished living room in a concrete building and a ranch structure. Because of the additional leakage air, the
fire in the concrete building does not become under ventilated when all exterior doors and
windows are closed, as the ranch structure does. The ranch structure behaves similarly to the
ideal vent limited fire curve, growing after ignition to a point where the fire becomes
underventilated, and only growing again once additional oxygen is provided. Instead, the fire in the concrete burn building
reaches a ventilation limited steady state, transitioning to flashover when a vent is
opened close to the fire. Even when all doors and windows to the concrete
burn building are closed, the fire is provided a constant supply of air via the leakage points
in the structure, allowing it to continue burning without becoming underventilated. Some instructors have found innovative ways
to modify concrete live fire training buildings to conduct ventilation limited live fire training. Since this may not always be possible, it
is important that instructors and students understand the difference in fire dynamics
between their training props and the fire ground.

  • In the Real World, that was pretty much useless. First of all, this talk will bore the average person to death. Second, it taught nothing about the best ventilation in various conditions and structure types. Third, nothing about water application to eliminate heat and toxic gas producing combustion. This won't be going into my Fire Fighting Training Playlists.

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