Ecology And Environment
NFDRS Levels

Determine Danger Level Forest Service Fire Hazard



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NFDRS Levels
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© www.fs.fed.us 2009 http://www.fs.fed.us/r8/boone/fire/wildfire/levels.shtml

The Daniel Boone National Forest estimates that nearly 7,000 acres of forest burn in an average of 150 fires every year (www.fs.fed.us, 2009).  Many of the annual fires are arson related, but not all of them.  In order to reduce the number of accidental fires, the public needs to have a better understanding of the National Fire Danger Rating System (NFDRS).   

The NFDRS  is a rating system put in place by the National Forest Service that estimates the probability that a fire will occur within a certain area.  It also determines how likely it is that a fire will spread  (http://fhsarchives.wordpress.com,  2008).  The current system uses adjectives ranging from low to extreme, mixed with a color coding system to represent the five levels of fire danger.  The level of fire danger is evaluated on an Ignition, Spread, Spotting, and Control  system.

IGNITION: A rating of the probability that a firebrand will cause an actionable fire.

SPREAD: A rating of the forward rate of spread of the head of a fire.

SPOTTING: Behavior of a fire producing sparks or embers that are carried by the wind and which start new fires beyond the zone of direct ignition by the main fire.

CONTROL: The completion of control line around a fire, any spot fires therefrom, and any interior islands to be saved; burned out any unburned area adjacent to the fire side of the control lines; and cool down all hot spots that are immediate threats to the control line, until the lines can reasonably be expected to hold under the foreseeable conditions.  (http://fhsarchives.wordpress.com, 2008). 

The following is a simple breakdown of each of the five levels:

Low—Fuels not readily ignitable, fires may burn freely in open grass after a rain, wood fires smolder and move slowly, little chance the fire will spot or spread, simple to control

Moderate—Fires easier to start by accident, grassland fires spread rapidly in wind, possible spotting,  usually not serious, easy to control

High—Fine dead fuels ignite easily, fires started by most causes,  spread rapidly, intense burning, short-distance spotting, may become serious with difficult control if not caught early

Very high—Fires very easy to start, spread immediately and rapidly, spotting danger constant, control difficult

Extreme—Fires start quickly, burn intensely, all potentially serious, spotting danger constant, very difficult to control—situational procedures to be followed  (http://www.fs.fed.us, 2009)

The origin of the NFDRS dates back to the 1940s, when a man named Harry T. Gisborne “developed a  simple slide rule–like device known as the Fire Danger Meter that foresters could carry with them in the field” (http://fhsarchives.wordpress.com, 2008).  From that initial design, other systems began to emerge, and in 1972 a “unified rating system was conceived, tested, improved, and subsequently made operational “ (http://fhsarchives.wordpress.com, 2008). 



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