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Visibility Range Index

As an additional tool, a visibility range index can be used to assess air quality. This method was developed specifically for wildfire smoke and should be used during daylight hours and only if the relative humidity is less than 65%:

  1. Focus on the darkest object on the horizon (e.g., black is better than green).
  2. Determine the limit of visual range by looking for targets at known distances (miles). The visible range is the point at which even high-contrast objects like a forested mountain totally disappear.
  3. After determining the visual range in miles, use the chart to identify actions to take to reduce exposure.

Sensitivity to smoke can vary greatly, and individuals can become more sensitive to smoke after extended periods of exposure. Individuals should pay attention to the advice of a medical professional or local health officials and adjust activity accordingly.

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