What is the preferred mixing height range?

What is the preferred mixing height range?

• A. 1,700-6,500 feet
• B. 500-1,000 feet
• C. 6,500-9,000 feet
• D. 0-500 feet

Answer: (A)

Mixing height is how high the air is stirred and mixed by convection, which determines how far and how quickly smoke from a burn will dilute before it reaches the ground again. For a prescribed fire, you want enough vertical mixing to dilute the smoke so it doesn’t linger heavily at ground level, but not so much that the plume rises and travels far beyond the burn area. The preferred range of 1,700 to 6,500 feet above ground level provides that balance. It’s high enough to allow substantial dilution of smoke, improving visibility and reducing ground-level concentrations near the burn, while not so high that the plume is carried unpredictably far by upper-level winds or escapes the local area entirely. If mixing height is too low (0–500 or 500–1,000 feet), smoke tends to stay near the surface and can create unhealthy conditions for people nearby and hinder firefighter safety. If it’s too high (6,500–9,000 feet), smoke disperses over a much larger area, which can complicate smoke management and visibility for nearby roads and communities.

Mixing height is how high the air is stirred and mixed by convection, which determines how far and how quickly smoke from a burn will dilute before it reaches the ground again. For a prescribed fire, you want enough vertical mixing to dilute the smoke so it doesn’t linger heavily at ground level, but not so much that the plume rises and travels far beyond the burn area.

The preferred range of 1,700 to 6,500 feet above ground level provides that balance. It’s high enough to allow substantial dilution of smoke, improving visibility and reducing ground-level concentrations near the burn, while not so high that the plume is carried unpredictably far by upper-level winds or escapes the local area entirely. If mixing height is too low (0–500 or 500–1,000 feet), smoke tends to stay near the surface and can create unhealthy conditions for people nearby and hinder firefighter safety. If it’s too high (6,500–9,000 feet), smoke disperses over a much larger area, which can complicate smoke management and visibility for nearby roads and communities.