Burning Index Explained

Burning Index (BI) is a number used by the National Oceanic and Atmospheric Administration (NOAA) to describe the potential amount of effort needed to contain a single fire in a particular fuel type within a rating area. The National Fire Danger Rating System (NFDRS) uses a modified version of Bryam's equation for flame length – based on the Spread Component (SC) and the available energy (ERC) – to calculate flame length from which the Burning Index is computed.^[1]

The equation for flame length is listed below:

F_L=j\left[\left(

	SC
	60

\right)(25(ERC))\right]^0.46

where:

j is a scaling factor,

SC is the spread component,

and ERC is the Energy Release Component.

Consequently, the equation for the Burning Index is:

BI=j_1 F_L

where

j₁

is the Burning Index scaling factor of (10/ft). Therefore, dividing the Burning Index by 10 produces a reasonable estimate of the flame length at the head of a fire. A unique Burning Index (BI) table is required for each fuel model.

Notes and References

Web site: National Fire Danger Rating System: Indices . wrh.noaa.gov . 2011-05-19 . https://web.archive.org/web/20110519200326/http://www.wrh.noaa.gov/sew/fire/olm/nfdr_ind.htm . 2011-05-19 . dead . 2020-04-29.