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Lesson Objectives

• List three elements used to determine fire danger rating.

• List the five ‘standard’ fire danger rating levels.

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Introduction

• Fire Prevention/Mitigation Specialists should constantly be aware of the fire weather conditions and forecasts. The fire danger affects most of what these specialists do on a day-to-day basis.

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Introduction

• This is an overview of the fire danger ratings, and the NFDRS and is not intended to be a lesson in fire behavior.

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The National Fire Danger Rating System

• Determines fire danger in the area

• Managers may impose restrictions/closures

• Pre-position resources

• Make fire management decisions

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The Importance of Fire Behavior to Fire Prevention

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• The importance of the basic aspects of fire behavior – ease of ignition, rate of spread, and the rate of combustion – cannot be over emphasized since they dictate what is needed to control a fire.

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• Fire behavior components are principle keys to fire danger rating.

• It sets the numbers that managers can use for limiting use, setting restrictions, and for fire planning.

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Understanding Fire Danger

• Fire Danger is a description of the combination of both constant and variable factors that affect the initiation, spread, and difficulty to control a wildfire.

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Understanding Fire Danger

• Since 1974, five Adjective Fire Danger levels have been used in public information and signing. Recently, several areas have added another administrative element. This is not the normal application, and is used here as information only.

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Fire Danger Level

• Fire starts are unlikely. Weather and fuel conditions will lead to slow fire spread, low intensity, and relatively easy control with light mop-up. Controlled burns can usually be executed with reasonable safety.

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Fire Danger Level

• Some wildfires may be expected. Expect moderate flame length and rate of spread. Control is usually not difficult and light to moderate mop-up can be expected.

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Fire Danger Level

• Wildfires are likely. Fires in heavy, continuous fuel will be difficult to control under windy conditions. Control through direct attack may be difficult but possible, and mop-up will be required.

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Fire Danger Level

• Fires start easily and may spread faster than suppression resources can travel. Flame lengths will be long with high intensity, making control very difficult. Suppression and mop-up will require an extended and very thorough effort.

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Fire Danger Level

• Fires will start and spread rapidly. Every fire start has the potential to become large. Expect extreme, erratic fire behavior.

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Fire Danger Level

• Information only. This element is being used in several areas as a management and public relations tool. When conditions are critical, (major fires, extreme weather forecasts, resource drawdown, natural disasters, etc.) this level is used.

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Fundamentals of Fire Danger

Fuel Moisture

• Live Fuels

• Dead Fuels

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Fundamentals of Fire Danger

Live Fuel Moisture

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Fundamentals of Fire Danger

Dead Fuels

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Fundamentals of Fire Danger

• Dead fuels

• 1 hour

• 10 hour

• 100 hour

• 1,000 hour

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Fundamentals of Fire Danger

Relative Humidity

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Drought Indicator Systems

• Several drought map systems are in use, the Keetch - Byram Drought Index (KDBI) is a common one.

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Keetch – Byram Indicators

• KBDI = 0-200

• KBDI = 200-400

• KBDI = 400-600

• KBDI = 600-800

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Lower Atmosphere Stability Haines Index

• 2 – Very low potential

• 3 – Very low potential

• 4 – Low potential

• 5 – Moderate potential

• 6 – High potential

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Energy Release Component

• Based on the estimated potential available energy released per unit area in the flaming front

• Variations caused by changes in fuel moisture contents

• Derived from predictions of rate of heat release

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Energy Release Component

• Defined as the potential available energy per square foot of flaming fire at the head of the fire and is expressed in British Thermal Units (BTU)

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Ignition Component

• The ignition component is a number that relates to the probability that a fire will result if a firebrand is introduced into a fine fuel complex.

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Spread Component

• The spread component integrates the effects of wind and slope with fuel bed and fuel particles to compute the forward rate of spread at the head of the fire. Output is unit of feet per minute.

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Summary and Review Lesson Objectives

• List the elements used to determine fire danger rating.

• List the five ‘standard’ fire danger rating levels.

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