N.C. Forest Service - Burning Categories
Mixing height x transport wind speed = ventilation rate
Example 1: Mixing height 6000 ft x transport wind speed 14mph = 84000 ventilation rate (category 4)
Example 2: Mixing height 4000 ft x transport wind speed 10mph = 40000 ventilation rate (category 2)
Ventilation Rate | Burning Category | Explanation of Category |
|---|---|---|
| 0 to 14,760 | 0 | No Burning |
| 14,760 to 33,499 | 1 | Inversion for most of the day. A short window may be available in mid-afternoon. DAYTIME BURNING ONLY |
| 33,500 to 44,999 | 2 | Inversion until early afternoon and very light transport wind. MID-AFTERNOON BURNING ONLY |
| 44,999 to 59,999 | 3 | Inversion until late morning. Light transport wind. DAYTIME BURNING |
| 60,000 to 111,999 | 4 | Little or no inversion. Moderate transport wind. BURN ANY TIME |
| 112,000 or greater | 5 | No inversion. Strong and gusty transport wind. BURN WITH CAUTION. GOOD SMOKE DISPERSION, BUT POTENTIAL SEVERE FIRE BEHAVIOR |
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This page was last modified on 01/09/2025