What is the definition of Moisture of Extinction (MOE)?

What is the definition of Moisture of Extinction (MOE)?

• A. Moisture content of a fuel which a fire will not propagate itself
• B. The moisture content at which fuels ignite
• C. The moisture content indicating when fuels become fully saturated
• D. The moisture content at which combustion becomes physically impossible

Answer: (A)

Moisture of Extinction measures the point at which a fuel’s moisture content is high enough that a spreading fire can no longer continue to propagate through the fuel bed. In other words, below this moisture level the fire can advance, but at or above it the flame cannot sustain forward spread under the given conditions. This threshold is specific to the fuel type and conditions (fuel size, arrangement, wind, temperature, etc.). It is not about the fuel igniting, nor about the fuel being fully saturated, nor about combustion becoming physically impossible in every sense. At MOE, ignition might still occur locally, and there can be some combustion, but sustained spread ceases. So the correct understanding is that MOE is the moisture content where propagation through the fuel is no longer possible, distinguishing it from ignition moisture, saturation moisture, or an absolute barrier to any combustion.

Moisture of Extinction measures the point at which a fuel’s moisture content is high enough that a spreading fire can no longer continue to propagate through the fuel bed. In other words, below this moisture level the fire can advance, but at or above it the flame cannot sustain forward spread under the given conditions.

This threshold is specific to the fuel type and conditions (fuel size, arrangement, wind, temperature, etc.). It is not about the fuel igniting, nor about the fuel being fully saturated, nor about combustion becoming physically impossible in every sense. At MOE, ignition might still occur locally, and there can be some combustion, but sustained spread ceases.

So the correct understanding is that MOE is the moisture content where propagation through the fuel is no longer possible, distinguishing it from ignition moisture, saturation moisture, or an absolute barrier to any combustion.