Does a Dehumidifier Help with Radon?

Radon In Homes How to Purify Air


Radon levels are a serious problem, regardless of whether you’re trying to sell your home or trying to stay in it.

We all know just how expensive it can get to try to remedy radon issues in a home, so it’s perfectly understandable for a homeowner to try to find less expensive, seemingly easier methods.

One idea floating around is that by reducing humidity levels in a home, somehow the radon levels would also decrease.

But can something like a dehumidifier really help with radon? No, buying a dehumidifier will not make radon go away. Research conducted by the US Environmental Protection Agency (EPA) has clearly disproved this idea. Radon must be removed by a remediation method like active soil depressurization (ASD), which ironically has been shown to be even more effective at removing humidity from a home than a dehumidifier in the same EPA study.


What the EPA’s Moisture Study Tells Us About Radon

In 2014 the EPA conducted a study to understand just what kind of effects active soil depressurization (ASD), the most effective method to reduce radon in homes thus far, has on the overall moisture levels inside a home.

The study was done on three Pennsylvania homes only, so it clearly leaves a lot more data and research to be desired. But still, it gives us clues on how to connect the dots between radon and humidity.

Here’s what the study tells us:

A radon remediation method like ASD will not only reduce radon levels in a home, but it will also dehumidify the home. A dehumidifier, on the other hand, won’t have any meaningful impact on radon levels.

In fact, a dehumidifier was only able to achieve 8% to 25% of the moisture capacity that the ASD did!

In other words, installing an ASD in your home not only removed radon, but it was doing the work of 4 to 13 dehumidifiers as well. But the reverse that a dehumidifier will also decrease radon levels wasn’t true.

So while radon remediation may cost $1,500 to $2,500 on average up front to be installed, compare that to the cost to run a dehumidifier that’s added on top of your yearly energy bill. And let’s not miss the obvious point here that it removes a dangerous carcinogen like radon.

Recommended reading: Does a Vapor Barrier Stop Radon?


How Radon Enters Your House

To understand why a dehumidifier won’t actively remove radon, we have to understand just how radon gets into your home and how it moves once inside.

Most radon enters the home through the soil. It seeps up through the pores and cracks of a foundation and walls. Block walls are more susceptible to radon entry since they’re more porous and as such, considered a weak water barrier. Radon also finds its way through sump pits and pumps.

(If you have a sump pump, now might be a good time to start looking into sump pump radon covers like this one from Amazon.)

As any other lightweight gas, radon is sucked into a home by means of negative pressure. The highest levels are in the basements and crawlspaces, and radon levels decrease with each new upper level of the house.


Why ASD Also Acts as a Dehumidifier

Most radon mitigation systems draw the air from underneath the slab through a hole, and then push the radon through vents that run up towards the roof to ultimately expel it to the outside with the help of a constantly running fan. This is known as sub-slab or active soil  depressurization, or ASD.

This method tends to achieve about a 90% success rate in most cases after installation when it comes to removing radon.

Naturally, the air from the soil is moist anyway. By applying enough fan pressure to move this air across several levels of a floor and to ultimately push it above a roof line, it makes sense that an ASD would be such a powerful dehumidifier in itself.

In fact, it was so powerful, the EPA moisture study showed that the ASD was also able to pull the air out from the building materials like the block walls to get the moisture out, while the dehumidifier only could extract moisture from the air that was already inside the home.


Why a Dehumidifier Won’t Decrease Radon

We’ve established that it takes a powerful fan, as well as closed, unidirectional vent system to push radon out of the home. A dehumidifier clearly isn’t strong enough to do this.

The image below demonstrates that running a dehumidifier clearly had no effect on the radon levels – see the red arrows.


(Source – EPA’s 2014 Moisture Study)


There’s a reason for this –

A dehumidifier is made of two main sections. The front part of it draws in the room temperature air and runs it across cold coils so that the water from the air can be condensed and collected into a container. After the air has been processed, it’s then reheated again and blown back into the room.

So the idea that a dehumidifier could remove radon doesn’t make much sense (as much as most of us would want this to be true). It’s a gas, so it clearly won’t end up in the water collection container or water hose. And even if somehow it were separated out inside the dehumidifier, it would just be pushed out into the same air on the back side.

So, this topic should be reworded to ask about humidity in general, not dehumidifiers.

Which leads me to how humidity levels impact radon levels inside the home, as well as short-term radon test kits.


Humidity and Short-Term Radon Test Kits

Generally speaking, radon can be tested with short-term or long-term tests. Short term tests usually require a minimum of 48 hours of data collection inside a home, although they may take as long as 7 days.

Tests lasting more than three months are considered long-term tests.

Even though short-term tests are convenient, they don’t tell the whole story. Radon levels naturally fluctuate, so it’s best to have as many data points that can be averaged out. Many radon test kits have also be found to be inaccurate by as much as 25% when tested in lab studies.

Another problem with those short-term tests is that many home sellers think that they can “trick” the radon test during a real estate transaction. Again, trying to time a radon test to barometric pressure, outside temperature, wind strength, and whether it rained that day can prove to be frustrating.

Radon readings are made up of many moving parts. Even scientists themselves haven’t worked this out, so any favorable results you get with your own test should be seen more as luck rather than deliberate.

Having said that, here are factors that are generally considered to be true:

  • Charcoal canister test kits are very sensitive to humidity levels, so they won’t be as effective when used as short-term tests.
  • Even though the EPA recommends that each home be tested for radon once every year, it’s a good idea to test a home for radon twice a year. That’s because radon levels tend to be at higher levels during the winter than the summer because the difference  in pressure between a heated home and frozen soil makes it easier for radon to move in.
  • Most radon test kits are calibrated to reflect wide ranges of temperature and relative humidity (RH) levels in a home, but many manufacturers recommend that a home not be tested at all until the RH levels are brought down to at least 55% or lower. This can be hard to do, especially in damp basements.
  • Outside barometric pressure can impact radon levels inside a home. Low barometric pressure typically signals precipitation, so it usually rains at low barometric pressure as well. Radon levels inside a home tend to rise several hours after low barometric pressure and high winds occur outside, so it’s not very wise to run a radon test right after a storm. Your radon levels will rise and appear to be abnormally higher than usual.



A single dehumidifier alone won’t help much with radon. Radon levels also rise and fall inside a home, so it can be difficult to gauge just how serious the issue is on your own.

Homes with serious radon issues will need to have a radon mitigation system installed throughout, which can be costly. There are alternative solutions like radon mitigation fans, although it’s preferable to have radon tested by professionals first.