Fire flows are used to rapidly gauge the expected amount of water needed for a given percentage of involvement of a structure fire.

Org Admins can control which fire flows are in use under Admin | Manage Organization:

Naturally, each structure and each circumstance is different. So you should use your own judgement.

If you have entered dimensions (at least Length and Width), you will see some automatic fire flow computed values appear.

Here is a good reference: "Determining Required Fireflow" (Rob Neale, Jan 2018)

Iowa State University Method

The Iowa State University (ISU) method was created in the 1950s after a series of studies of fire in enclosed spaces. The ISU “Ideal Rate of Flow” formula:

Using the ISU formula, an IC can assess the conditions at a burning noncombustible mercantile occupancy that measures 50 feet by 75 feet and is one story (12 feet) tall. The IC can quickly determine that the volume of the structure is 45,000 cubic feet. Using this number and the ISU formula, the required fire flow for this structure would be 450 gallons per minute (45,000 ÷ 100 = 450).

National Fire Academy Method

The National Fire Academy (NFA) formula, taught in the Managing Company Tactical Operations (MCTO) classes, is similar to the ISU method, but employs different values and is based on area, not volume. The NFA fire flow formula is:

Using the same example, an IC arrives at a burning mercantile occupancy that measures 50 feet by 75 feet and is one story (12 feet) tall. The IC quickly determines that the area of the structure is 3,750 square feet. Using this number and the NFA formula, the required fire flow for this structure would be 1,250 gallons per minute (3,750 ÷ 3 = 1,250).

More complicated formulas exist that take into account properties such as construction type, occupancy, rural water supplies:

Refer to the article mentioned above for additional information on these more complicated computations.
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