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Visibility Ranges


Health Effects Categories
Visibility Ranges
(miles)3
  Hazardous < 1.3
  Very Unhealthy 2.1 - 1.3
  Unhealthy 5.0 - 2.2
  Unhealthy for Sensitive Groups 8.7 - 5.1
  Moderate 13.3 - 8.8
  Good > 13.4 +

The procedure for making personal observation to determine the forest fire smoke index value for local areas without National Weather Station (NWS) or Department of  Environmental Quality (DEQ) monitors is:

  1. Face away from the sun.
  2. Determine the limit of your visible range by looking for targets
    at known distances (miles).
  3. Visible range is that point at which even high contrast objects
    totally disappear.
  4. Use the values above to determine the local forest fire smoke
    category.