How to Estimate Air Quality Only Using Your Eyes

The 5-3-1 index can help you understand and estimate the air quality at any time, from any location.

Posted: Jul. 23, 2018 7:52 PM

MEDFORD, Ore. -- Wildfires are burning in remote areas, sending smoke across almost all of southern Oregon.  While the Department of Environmental Quality monitors air pollution throughout the state, not every community has an official monitoring station. Even where there is an air quality monitoring site, smoke levels can rise and fall more rapidly than the monitoring sites can update.  Those are reasons why experts recommend visual observations for air quality health alerts.

Experts say the "5-3-1 visibility index is a simple way of estimating smoke levels and what precautions to take." While this method can be a useful tool, it's not 100% accurate.  You start by determining how many miles you can see, based on your knowledge of the distance to a mountain, signage, or other landmark. The DEQ suggests "a general rule of thumb: if you can clearly see the outlines of individual trees on the horizon it is generally less than five miles away."  They recommend positioning yourself so the sun is behind you.

Once distance has been determined, follow this simple guide:

5

If visibility is well over five miles, the air quality is generally good.

Even if visibility is five miles away but generally hazy, air quality is moderate and beginning to deteriorate, and is generally healthy, except possibly for smoke sensitive persons. The general public should avoid prolonged exposure if conditions are smoky to the point where visibility is closer to the 5-mile range.

If under five miles, the air quality is unhealthy for young children, adults over age 65, pregnant women, and people with heart and/or lung disease, asthma or other respiratory illness. These people should minimize outdoor activity.

3

If visibility is under three miles, the air quality is unhealthy for everyone. Young children, adults over age 65, pregnant women, and people with heart and/or lung disease, asthma or other respiratory illness. These people should minimize outdoor activity.

1
If under one mile, the air quality is unhealthy for everyone. Everyone should avoid all outdoor activities.

No matter how far you can see, if you feel like you are having health effects from smoke exposure, take extra care to stay inside or get to an area with better air quality. You should also see your doctor or other health professional as needed.

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