Because smoke conditions can change rapidly, it is best to use the Smoke Visibility Index for your specific location.
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:
Face away from the sun.
Determine the limit of your visible range by looking for targets at known distances (miles).
Visible range is that point at which even high contrast objects totally disappear.