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Radon Entry

Radon Reduction Techniques

Air pressure inside your home is usually lower than pressure in the soil around your home’s foundation.  Because of this difference in pressure, your house acts like a vacuum, drawing radon in through foundation cracks and other openings. Radon may also be present in well water* and can be released into the air in your home when water is used for showering and other household uses. In most cases, radon entering the home through water is a small risk compared with radon entering your home from the soil.  In a small number of homes, the building materials can give off radon, although building materials rarely cause radon problems by themselves.

*Note: In Illinois, Radon levels have never been found high enough in water to cause an indoor air problem.

Radon can enter through cracks, sumps, drains, block walls and open block tops.

Radon can enter through most surfaces in contact with the soil, even concrete. As concrete dries micro fractures occur throughout which allows the radon gas to pass through into the living area.

Remember radon is so small that we can’t see it, in turn the cracks and pathways for radon to enter can be so small that you can’t see them either.

If you understand the above, and don’t want to get confused don’t read any further.

Not every crack or sump pit is a source of radon
Here is the tough part, it is possible to seal the sump, seal visible cracks and have your radon levels increase. WHY? Let’s use the sump pit below as an example.  In most cases the sump pit will contribute to your radon problem but in a few cases (let’s say 1 in 8) the sump pit is a source of dilution air – air that will reduce your radon levels, notice I did not say fresh air, sump pits are usually a source of biological contaminates and should always be covered, but that’s another subject.


As shown in this illustration, the dilution air travels from outside, down through the window well drain and into the basement from the open sump pit.  It is impossible to know for certain if sealing the sump will reduce the radon levels or increase them, nevertheless the sump pit must be sealed for an active radon reduction system to work properly and for passive radon reduction also. This is just an example of one possible reason radon levels could increase after sealing alone has been performed. I warned you this could get confusing but more importantly it is an another example of why sealing alone does not work.