Why Do Fires Burn Differently at High Altitudes?

Lower Oxygen Levels Affect Combustion

At high altitudes, oxygen levels decrease by approximately 20-30% for every 1,000 feet of elevation gain. This reduction in oxygen affects the combustion process, as fires require a specific amount of oxygen to sustain themselves. In general, fires burn at a slower rate at high altitudes due to the reduced oxygen availability. For example, a fire that burns at 1,000 pounds per hour at sea level may only burn at 600-800 pounds per hour at 5,000 feet.

Lower Air Pressure Impacts Temperature and Flames

The lower air pressure at high altitudes also impacts the temperature and flames of a fire. In general, the temperature of a fire decreases with increasing altitude. For example, a fire that burns at 1,200 degrees Fahrenheit at sea level may only burn at 900-1,000 degrees Fahrenheit at 5,000 feet. Additionally, the lower air pressure can cause flames to become more disorganized and less intense.

Implications for Fire Management

Understanding the effects of high altitude on fire behavior is crucial for effective fire management. Firefighters and land managers must take into account the reduced oxygen levels and lower air pressure when assessing fire risk and developing fire suppression strategies. For example, fires that may appear less intense at high altitudes may still pose a significant threat due to the reduced oxygen levels and increased spread rates.