Ch 8 Flashcards
(44 cards)
In fire attack, the offensive versus defensive decision is based on:
Staffing available to conduct the interior attack, water supply, ventilation, and most importantly a risk versus benefit analysis.
Rate of flow is also a major factor in determining if resources are adequate.
Regarding rate of flow, the essential question to be answered when addressing extinguishment is
How many gpm are required to extinguish a given fire with properly placed hose lines
The capability of a hose stream to extinguish a fire will generally be determined
In about 30 seconds. If you don’t darken the fire within 30 seconds, you need more water.
This is included in the Royer/Nelson formula
The major assumption of Royer and Nelson is that structure fires are primarily ventilation control
When calculating rate of flow, the Royer/Nelson method is to
Determine the volume of the fire compartment divided by 100 or
V/100= GPM
This formula is based on the assumption that fuels will produce a given heat quantity per volume of air regardless of the fuel size and type
A “ residential mentality” refers to
The failure to recognize the need for larger fire streams. Always using the same size hose line even in large commercial buildings.
The “trial and error” method of fire attack is when
Firefighters use their favorite preconnected hose line, then when they are unsuccessful, they add more lines of the same kind/size.
The success rate of trial and error is dependent on the flow rate and size of the preconnected line
The national fire Academy method of calculating rate of flow is
Area in square feet divided by three equals GPM or
(A*A)/3=GPM
this factor determines whether fires are typically fuel controlled or ventilation control
The volume of the compartment or area.
Ventilation controlled fires require less water than free burning fires
Fires in large open areas require higher rate of flow.
The major difference between Backdraft potential and flashover potential is
Backdraft require an oxygen starving environment
Flashovers require an oxygen sufficient environment
The normal attack rate of flow for most departments is equal to
Equal to two standard preconnected hose lines. Usually 1.75”
The weakness in both the Royer/Nelson and national fire Academy formulas are that they…
Alternatively, sprinkler system calculations represent …
Ignore the fuel load and the fuel type. They only consider the size of the compartment.
Sprinkler system calculations typically include both fuel load and fuel type
In a compartment or segmented building, rate of flow should be calculated for
The largest single compartment on fire, not the entire floor area
Each compartment can be handled as a separate fire and can be extinguished in one room at a time.
Pre-incident planning the rate of flow in buildings that exceed… is highly recommended
Buildings that exceed the capability of two standard attack hoselines
The book recommends using the V/100 method for pre-incident planning when the rate of flow exceeds to standard attack hose lines
The national fire Academy method recommend a percentage of involvement modifier in its calculations. This is:
Divide the total flow by the percentage of involvement of the compartment of building.
Example, 25% of the floor area is involved then divide the total flow by 4.
The Royer/Nelson formula does not include a modifier in the volume calculations
According to the book, most fires that are in their ignition phase can be controlled by
Less than 1 GPM
The book recommends this calculation during pre-incident planning, and this calculation on the incident scene
During pre-incident planning the book recommends the V/100 method
On the incident scene, the A/3 method with a percentage modifier should be used
Both of these should render similar results
Sprinkler rate of flow calculations are not suitable for unseen use endless. They are preplanned. This is because the sprinklers are.
Much more efficient than manual operations in getting water onto the fuel
When estimating rate of flow, overestimation is best. Unless it causes.
A delay in aggressive, interior attack, or leads to a defensive or non-attack decision because of a perceived lack of resources
According to Royer/Nelson, the assumption is getting water into the immediate fire area at what percentage of efficiency
80% efficiency.
This is also the assumption that the flow should be sufficient to knock down a fire within 30 seconds.
Since the amount of work effort is similar in using a 1.5” vs a 1.75” hose line, the book recommends the
1.75” as a minimum for an attack line
When making the decision on which hose line to use, you should
Let the occupancy determine the hose line.
Commercial 2.5” versus residential 1.75”
In regard to nozzle pressure, pump, discharge pressure, and flow rates, the most important point is that
Departments should flow test or nozzles on a regular basis to ensure the expected flow rate is being achieved.
This should be done with a calibrated flow meter on the intake side, and a pressure gauge in the discharge hose line both behind the nozzle and 100 feet back from the nozzle.
1.75” hose layouts should be no longer than
No longer than 250 feet due to excessive friction loss. Larger diameter hoses should be used to lengthen the layout if needed 
NFPA 14 requires a sign to be posted at the main control valve stating the location of the two most hydraulically remote hose connections, and
The designed flow and pressure at those locations.
Standpipe outlets with residual pressure exceeding 100 psi or static pressure exceeding 175 psi are required to have pressure reducing valves
