Atmospheric dispersion is the process by which the atmosphere mixes and transports particulates, such as smoke, away from their source. The Atmospheric Dispersion Index (ADI) was developed by the U.S. Forest Service to assess the impact of prescribed burning activity on atmospheric smoke concentrations and air quality. The same processes responsible for good smoke dispersion also contribute to erratic fire behavior and may present very hazardous conditions.

Interpretation of Daytime ADI Values

• 0–20: Poor dispersion, stagnant if persistent.
• 21–40: Poor to fair, stagnation may be indicated if accompanied by low wind speeds.
• 41–60: Generally good.
• 61–80: Very good dispersion. 75 and above, control problems likely.
• 80+: Excellent dispersion, control problems expected.

Interpretation of Nighttime ADI Values

• 0–2: Poor.
• 3–4: Poor to fair.
• 5–8: Good.
• 8+: Very good.