New "Radium-Containing Soil" graphic to include in your home inspection report

Here’s a new “Radium-Containing Soil” graphic to include in your home inspection report. Illustrated by Jackson.

The illustration shows the sources of radon that can accumulate in homes.

Most radon in homes comes from radon in the soil that seeps into homes through cracks in the foundation or slab. The amount of radon in the soil varies widely and depends on the chemical make up of the soil. There can be a large difference in radon concentrations in the soil from house to house. The only way to know is to test.

Radon is also found in the water in homes, in particular, homes that have their own well rather than municipal water. When the water is agitated, as when showering or washing dishes, radon escapes into the air. However, radon from water in the home generally contributes only a small proportion (less than 5%) of the total radon in indoor air in most housing. Municipal water systems hold and treat water, which helps to release radon, so that levels are very low by the time the water reaches our homes. But, people who have private wells, particularly in areas of high radium soil content, may be exposed to higher levels of radon.

EPA estimates that the national average indoor radon level in homes is about 1.3 pCi/l of air. We also estimate that about 1 in 15 homes nationwide have levels at or above the level of 4 pCi/l, the level at which EPA recommends taking action to reduce concentrations. Levels greater than 2,000 pCi/l of air have been measured in some homes. The only way you can know if there is radon in your home is to test for it.

Take InterNACHI’s free online radon course at

Our free inspection-related graphics library is really coming along: