The Burning Index is a number related to the contribution of fire behavior to the effort of containing a fire. The BI (difficulty of control) is derived from a combination of Spread Component (how fast it will spread) and Energy Release Component (how much energy will be produced). In this way, it is related to flame length, which, in the Fire Behavior Prediction System, is based on rate of spread and heat per unit area. However, because of differences in the calculations for BI and flame length, they are not the same.
The BI is an index that rates fire danger related to potential flame length over a fire danger rating area. The fire behavior prediction system produces flame length predictions for a specific location (Andrews, 1986). The BI is expressed as a numeric value related to potential flame length in feet multiplied by 10. The scale is open-ended which allows the range of numbers to adequately define fire problems, even during low to moderate fire danger.
A cross reference for BI to potential flame length, fireline intensity and descriptions of expected prescribed burning and fire suppression conditions is provided in Table 1 (adapted from Deeming et al. 1977). It is important to remember that a computed BI value is an index representing the near upper limit to be expected on the rating area. In other words, if a fire occurs in the worst fuel, weather and topography conditions somewhere in the rating area, these numbers represent the potential fireline intensity and flame length. These conditions are not expected throughout the entire fire danger rating area at any one time or under less severe conditions. Local relationships of fire danger outputs to fire activity are also portrayed effectively on Fire Danger PocketCards.
Burning Index/Fire Behavior Cross Reference