Test your knowledge on calculating rate of flow for fire suppression

10 Questions

What is the purpose of pre-incident planning for rate of flow?

To determine the number and size of hose lines needed

What are the two main formulas for rate of flow calculation?

V/100 and A/3

What is the preferred formula for rate of flow calculation?

V/100

What should be the backup hose line size for a structure fire?

At least as large as the initial line

What is the recommended pre-incident planning rate of flow threshold?

250 GPM

What is the volume to be pre-incident planned?

25,000 ft3 or larger

What is the standard preconnected hose line for structure fire?

Four sections of 1¾-in. (44-mm) hose

What is the recommended approach for determining rate of flow?

Use a combination of methods, with pre-incident planning using the V/100 formula and sprinkler calculations for heavy fuel loads

What is the recommended modifier for rate of flow calculations by the National Fire Academy?

Percentage-of-involvement

What type of structures require interior 2½-in. (64-mm) hose lines or interior master stream appliances?

Undivided structures with a large area on fire

Study Notes

Calculating rate of flow is important in determining the amount of water needed to extinguish a fire.
Pre-incident planning for rate of flow is highly recommended to avoid estimating the size of the involved compartment.
A/3 and V/100 calculations are used to estimate the rate of flow needed, but they only provide rough approximations.
Undivided structures with a large area on fire require interior 2½-in. (64-mm) hose lines or interior master stream appliances.
Pre-incident planning by general occupancy type is useful in determining the number and size of hose lines needed to combat fires in dwellings, apartment buildings, and small businesses.
The successful use of 1-in. (25-mm) booster hose ("red line") tends to verify the V/100 formula.
The National Fire Academy recommends a percentage-of-involvement modifier in applying the A/3 rate of flow.
It takes less water to extinguish a smaller fire than a larger fire.
The first company advancing to the fire area will provide the reconnaissance needed to determine the fire area in terms of percentage of involvement and compartmentation.
Advancing small-diameter preconnected hose lines is faster than advancing 2½-in. (64-mm) hose.
Rate of flow calculation is important for determining the size and number of hose lines needed to extinguish a fire.
Two main formulas for rate of flow calculation are V/100 and A/3.
V/100 is preferred and based on a substantial body of research.
Sprinkler calculations can also be used to determine rate of flow.
NFPA 13 and NFPA 1142 provide standards for sprinkler systems and water supplies.
The National Fire Academy recommends a percentage-of-involvement modifier for rate of flow calculations.
Sprinkler flow densities should be applied to the entire compartment when used to determine rate of flow using hose lines.
The best approach is to use a combination of methods, with preincident planning using the V/100 formula and sprinkler calculations for heavy fuel loads.
The IC can more accurately determine the size and number of fire lines needed with the rate of flow calculated in advance.
Standard preconnected hose lines are four sections of 1¾-in. (44-mm) hose with an automatic nozzle and a predetermined pump discharge pressure of 150 psi (1034 kPa).
Preconnected line for structure fire is 125 GPM (473 L/min)
Backup hose line should be at least as large as initial line
Preincident plan rate of flow threshold is 250 GPM (946 L/min)
Volume to be preincident planned is 25,000 ft3 (708 m3) or larger
Auto parts store example has three floors with varying hazard levels
Rate of flow is one reason to preincident plan a building
A/3 formula may be used if fire flow has not been preplanned
IC may be at a disadvantage if calculations are not accurate
SOPs should require preincident planning for structure fires
Sprinkler calculations may be recommended for extra hazard areas.