Fire Intensity: An In-Depth Guide

Dive into the science of fire intensity with the Western Fire Chiefs Association. Explore the factors that make fires rage, from fuel to weather conditions.

In the context of wildfires, understanding fire intensity is crucial to develop effective strategies for managing and mitigating wildfires. This comprehensive guide breaks down the details of the science of fire intensity, fire severity, and burn severity.

What is Fire Intensity?

Fire intensity serves as a metric to assess the power of a fire, taking into account factors like how much energy it releases and the features of its behavior, like how tall the flames are and how quickly they spread.

Is There a Fire Intensity Scale?

There is a fire intensity scale that serves as a measuring tool that helps determine the strength and severity of a wildfire. It considers factors such as how high the flames are, how fast the fire is spreading, and how much heat it is giving off.²

There are various levels on the scale to describe the intensity:

• Low Intensity: Flames are low, staying close to the ground making the fire spread slowly. Not much heat is produced which makes it more manageable.
• Moderate Intensity: Flames are a bit higher but only by a few inches so the fire spreads at moderate speed with moderate heat produced.
• High Intensity: Flames are high and can be tough to control. The fire moves considerably faster and can be a challenge. The heat coming from the fire has noticeably increased in temperature.
• Extreme Intensity: Flames are extremely high, towering above everything. The fire spreads extremely fast and is hard to predict. The substantial heat generated poses a significant threat to people and nature.

Why is Fire Intensity Important?

Fireline intensity is a crucial metric for gauging how likely a fire is to spread and how challenging it will be to control. It plays a significant role in fire behavior models that guide firefighting strategies. Firefighters and others rely on this scale to assess the seriousness of a fire and determine the best approach to manage it. This helps them decide where to concentrate their efforts and ensures they take the right steps to keep people safe. Understanding the intensity of a fire is essential for making informed decisions and minimizing its impact on both communities and the environment.¹

Fire Intensity vs. Fire Severity

Fire intensity is measured while the fire is actively burning. It considers things like flame size and how quickly it spreads. Fire Severity refers to the immediate impact the fire has on the ecosystem after the fire is no longer active. Specifically, fire severity assesses the amount of damage the fire did to trees, soil, wildlife, and the overall biodiversity of an area. Fire intensity helps firefighters deal with the fire at the moment, while fire severity helps them understand the long-term effects on the land and plan for recovery.³

What is Burn Severity?

Similar to fire severity, burn severity looks at the damage done after a wildfire has passed, but on a long-term and more direct scale. Burn severity focuses on the damage done to vegetation and the soil, measuring the extent of vegetation loss and the depth of soil damage.⁴