Tecnobosque

Smoke Ventilation Calculator | Mixing Height × Transport Wind

Tecnobosque · Wildfire Smoke Engineering Tool

Smoke Ventilation Calculator

Calculate wildfire-smoke ventilation rate from mixing height and transport wind. The physical result stays separate from any agency-specific smoke-dispersion category.

Ventilation Rate = Mixing Height × Transport Wind

Atmospheric inputs

Use the vertical reference reported by the issuing weather service. AGL and MSL are not interchangeable.
Transport wind is a mixed-layer average, not the same quantity as surface wind.
Operational categories are jurisdiction-specific. The calculation itself does not change.
Ventilation rate 60,000 knot-ft
9,408 m²/s
Selected profileGoodNWS 40 / 60 / 100 / 150k knot-ft
MIXING HEIGHT4,000 ft AGL
TRANSPORT WIND15.0 kt
KNOT-FT ×100060.0
PHYSICAL MEANINGDispersion potential
Important: a higher ventilation rate indicates greater atmospheric potential to transport and dilute smoke under the selected convention. It does not directly predict PM2.5 at a community, prove that smoke disappears or authorize prescribed burning.

What does ventilation rate mean?

Ventilation rate combines the depth of the mixed layer with the average wind through that layer. The U.S. National Weather Service commonly expresses this product in knot-feet for smoke-dispersion planning.

Worked example

Mixing height = 4,000 ft AGL and transport wind = 15 kt. Therefore 4,000 × 15 = 60,000 knot-ft. Under the selected NWS profile, that enters the Good category.

Ventilation rate is not air quality

A high ventilation rate does not guarantee low PM2.5 at a particular community. Smoke can be transported rapidly downwind, and local concentration still depends on emissions, plume rise, stability, terrain, vertical structure and time.

Mixing height vs plume height

Mixing height describes the turbulent atmospheric layer. Plume height describes how high smoke from a particular fire reaches. They are related but not interchangeable.

Transport wind vs surface wind

Transport wind represents an average through the mixed layer. Surface wind describes near-ground conditions. Do not substitute one for the other when reconstructing smoke transport.

Wildfire Knowledge Graph

Fire Weather → Mixing Height → Transport Wind → Ventilation Rate → Smoke Dispersion → PM2.5

Interpretation checklist

  • Use mixing height and transport wind from the same forecast period.
  • Check whether mixing height is AGL or MSL.
  • Keep units consistent before multiplication.
  • Preserve the issuing agency and its category convention.
  • Do not convert ventilation rate directly into PM2.5 or AQI.
  • Consider terrain, inversions, plume buoyancy and transport direction.

Technical reference

National Weather Service — Smoke Dispersal and Ventilation Rates

Tecnobosque Engineering Tool · reviewed September 2026 · Educational and planning use. Not an operational burn authorization or public-health forecast.