Master Plan Nashua Fire Rescue, NH
The prompt arrival of at least four personnel is critical for structure fires. Federal regulations (CFR 1910.120)
require that personnel entering a building involved in fire must be in groups of two. Further, before personnel
can enter a building to extinguish a fire, at least two personnel must be on scene and assigned to conduct
search and rescue in case the fire attack crew becomes trapped. This is referred to as the two-in, two-out
rule. However, if it is known that victims are trapped inside the building, a rescue attempt can be performed
without additional personnel ready to intervene outside the structure. Further, there is no requirement that
all four arrive on the same response vehicle. Many fire departments rely on more than one unit arriving to
initiate interior fire attack.
Perhaps as important as preventing flashover is the need to control a fire before it does damage to the
structural framing of a building. Materials used to construct buildings today are often less fire resistive than
the heavy structural skeletons of older frame buildings. Roof trusses and floor joists are commonly made with
lighter materials that are more easily weakened by the effects of fire. “Light weight” roof trusses fail after
five to seven minutes of direct flame impingement. Plywood |-beam joists can fail after as little as three
minutes of flame contact. This creates a dangerous environment for firefighters.
In addition, the contents of buildings today have a much greater potential for heat production than in the
past. The widespread use of plastics in furnishings and other building contents rapidly accelerate fire spread
and increase the amount of water needed to effectively control a fire. All of these factors make the need for
early application of water essential to a successful fire outcome.
The next figure illustrates the sequence of events during the growth of a structure fire over time.
Figure 116. Fire Growth vs. Reflex Time
Fire Growth vs Reflex Time
Z™ lashover
CPAP AR POPP? PE? EEE? PEP EEE LP Po? ? PE? AAPL ES
Temperature
T
;
re Growth
Hl
T
5
Minutes
1 2 6 7 8 9 10
ime Varies > _
=
5s S
Fire System Response Time 2 =
Detection] Report SP
Ign of of + Ss 5
Fire Alarm | Dispatch | Turn Set fa 3
of Out Respond to Scene up ss
Units =
ui
Time indirectly Time directly manageable
manageable by Fire Service System
<< __ __—______. Reflex Time _
Emergency Services
ESC) Consulting International 165
