Running head: LIMITING OR SPREADING OF A STRUCTURE FIRE 1

Limiting or Spreading of a Structure Fire

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Class XXXX, Section XXXX, Autumn 2012

LIMITING OR SPREADING OF A STRUCTURE FIRE 2

Limiting or Spreading of a Structure Fire

Structure fires are characterized by increased complexity, especially as their size grows.

Therefore, they require more attentive and precise analysis to ensure the right choice of a fire

attack strategy, namely offensive, transitional, or defensive, and other firefighting actions.

Within the offensive strategy, firefighters operate inside the building in order to limit the

spread of fire and localize it by an aggressive, direct, and fast attack. Herewith, hose lines are

advanced to deliver water exactly to the fire seat (Avillo, 2002, pp. 132-133; Shackelford, 2009,

p. 104). Naturally, the choice of the right lines and ensuring the necessary fire flow are of great

importance. For example, for a fully-involved one-story dwelling, two 1.75-inch (45-mm) lines

with a weaker fire flow (150 gpm) can be used. For larger dwellings, firefighters should use 2.5-

inch (64-mm) lines to attack fires, while single-family house fires can be attacked by one such

line. As soon as the fire is extinguished, smaller lines can be used again, as they are more

maneuverable and, while reducing water damage, release personnel for other works

(Shackelford, 2009, p. 120). On the whole, it is crucial to ensure proper size and pressure of hose

streams, their effective advancement, and proper fire flow (bigger buildings and fires require the

use of stronger capacities) (Shackelford, 2009, p. 141). Obviously, offensive attacks require

stronger lines and fire flows to ensure immediate effect, while defensive attacks may need more

lines to limit exposure.

Herewith, firefighters can use water in different ways to limit fire spread, e.g. straight

stream and fog or spray applications (especially for offensive attacks), water mist systems (for

water sensitive areas with electronic equipment), and foams (for different fire classes, with

different expansion ratios, and in wet, dry, or fluid forms). Additionally, they can choose from

dry chemicals, carbon dioxide, and halogenated agents (Shackelford, 2009, pp. 83-94).

LIMITING OR SPREADING OF A STRUCTURE FIRE 3

As the possibility of fire localization in the area of origin decreases and the fire is gaining

headway after a twenty minute offensive attack, the strategy should become more defensive.

When the fire becomes so huge that water streams should be used outside collapsed zones or

from a certain distance, defensive attacks are taken. Herewith, exposure protection becomes the

major goal due to larger external risks (Avillo, 2002, pp. 134, 138).

Apart from fire attack strategies, firefighters should perform other activities to limit the

spread of fire and smoke. As fires may spread very fast and buildings may have very

complicated structures, command posts should constantly monitor the situation, including

interior conditions, the building’s roof, and sides. This enables them to react in time and change

their actions accordingly (Avillo, 2002, pp. 132-133).

The latter include the reduction of temperature, removal of heat and fuel, use of chemical

chain reactions, and oxygen depletion (Shackelford, 2009, pp. 79-80), as well as various

supportive activities, i.e. forcible entry, primary search of victims, and ventilation. Effective

ventilation requires the knowledge of the building layout and awareness of the presence of

materials creating toxic fumes and burning hotter. Modern buildings and dwellings are more

insulated and less ventilated and have increased fire load, greater subdivision into rooms, and

many openings and holes, unprotected with fire dampers (i.e. central heating, ventilation, and air

conditioning systems), all of which fosters the spread of fire and smoke. For instance, in large

stores and malls, most fires occur in ground floors and basements, where fire attacks can be

performed only through an opening in the ceiling (Shackelford, 2009, pp. 120-122, 138).

Natural openings, such as skylights, scuttle holes, elevator shafts, and stairwells, can be

used for ventilation. However, if they are in the wrong place, they are of little value and can even

worsen the situation (Shackelford, 2009, pp. 143-144). Thus, roof ventilation can be the best

LIMITING OR SPREADING OF A STRUCTURE FIRE 4

choice, ensuring the release of gases and prevention of their horizontal movement. As soon as

the location for roof ventilation is determined, the opening should be started. Firefighters may

cut a large hole (about 80 ft2) directly over the fire. Herewith, the roof should be sounded before

cutting holes to ensure that it is safe, especially in lightweight constructions, namely the

buildings created after 1960. Cutting a hole directly over the fire assumes that this is the hottest

and most dangerous spot on the roof. Moreover, there is always a risk of falling through the roof

and being killed. Therefore, holes can be cut within 20 ft of the fire base without significant

redirection of the fire and gases. Herewith, as some people may be trapped, fire and smoke

should be redirected with the help of ventilation to save them. Additionally, louvering can be

used to ventilate the roof, decrease smoke and heat streams, and direct them from the working

area (Shackelford, 2009, pp. 122, 144-145).

Also, firefighters can use cross ventilation, while opening doors, windows, and other

horizontal openings (or breaking them out), as well as smoke fans. In case they are large enough

and in a sufficient number, such horizontal ventilation can limit smoke, smoke damage, and life

hazards. However, wind, smoke, and fire direction should be determined first in order to avoid

their further spread to adjoining buildings and rooms or upper rooms.

Additionally, a burst of water at the ceiling will help to cool the heated gases in the upper

levels of the room and enable firefighters to use direct attacks, while water appliances can reduce

and redirect hot air and gas masses and cool larger surfaces. Also, the water steamed down the

side of an exposed building can limit exposure to radiant heat (Shackelford, 2009, pp. 104, 116).

On the whole, firefighting activities should be properly planned and assorted with fire,

building, and weather peculiarities, as inability to realize a fire attack and take supportive actions

properly can worsen the situation and foster the spread of fire.

LIMITING OR SPREADING OF A STRUCTURE FIRE 5

References

Avillo, A.L. (2002). Fireground Strategies: Fire Engineering. Tulsa, OK: PennWell Books.

Shackelford, R. (2009). Fire Behavior and Combustion Processes. Clifton Park, NY: Delmar

Cengage Learning.