When I go out to give an estimate to people who are selling their home, there are usually a couple of frequently asked questions...


How dangerous is radon?

Why does my house (but not my neighbor's) have radon?

How does a radon mitigation system work?

What does the fan do?

Why must the system reach beyond the house?

For houses with slabs, do you drill a hole? Where do you drill?

Are system fans noisy?

Why do fans have to be outside or in the attic?

Could a fan increase radon levels by drawing from the ground surrounding the house and into the basement?

How much does system maintenance cost?

Is there any difference between interior and exterior installation?

Do ceiling fans and humidifiers help to reduce Radon?


While viewing the house, usually we start in the basement by looking for holes and gaps, and I'll talk about the radon passages - where it's coming from and why it accumulates in your house. Often I take a piece of paper and draw the house and how air moves up from the soil and becomes trapped by the huge surface area that your house occupies.

The process where this air pressure (and Radon) that finds a release point into the house is called depressurization: air moves where there is the least resistance and where there's a vacuum. That's why a radon mitigation system is often called a sub-slab depressurization System.

Next, people want to know: how dangerous is Radon really?

Well, the fact is that radon is the second leading cause for lung cancer. The radiation of alpha particles in Radon are ten times stronger than x-rays!! And when a person is inside the house for many hours, working out in the basement, breathing in concentrated Radon in air, they can experience a radiation charge, that although minimal, can destroy lung cells. Then, when the body regenerates and reproduces lung cells, many things can go wrong and that's where cancer cell growth occurs.  This way, the gas can lead to cancer.

That being said, a lot of people are panicking about radon levels even if they are not significantly elevated. And they won't buy a house until it is reduced to comfortable level. It's important to remember that there are many other cancer causing agents to consider. Cancer is a very complex reaction in your body and other factors like chemicals, environmental hazards, fumes that we are so used to, food, exercise, our psyche…. everything plays a role. I'd like to spread the information a bit wider and not focus exclusively on radon regarding lung cancer. My advice is always to open or crack the window for fresh air, and movement, as much as possible. For example just a window cracked open for an inch or two can reduce radon levels in your home to a very safe level.

For some people radon is not a health concern, but they just wonder why their house has radon and the neighbor’s does not?

Here's how it happens: there is movement of air in the soil. You can have certain areas where air gathers, and that pocket might be just under your house and not the neighbors. And the only way to find out is through testing. I explain that there are different types of testing equipment: active and passive, the cheapest of which is the charcoal activated tests (from Lowe's), and the most expensive being the radon monitor, which is a Geiger counter that actively analyzes the air for radon content. It measures every hour and calculates an average an end of the testing period. This technology allows for exact measurements that only have a variation of 3 to 5% , whereas the charcoal canister can vary up to 25%, so you get what you pay for. With a charcoal test you will not be able to see the highs and lows shown by the hourly readings of the monitor, so the passive sample test can only absorb so much and usually is reflects the last 8 hours of testing.

Then the people want to know: how does a system work?

As explained earlier, we de-pressurize the soil or the sub slab by creating a vacuum and pulling the air towards the pipe. A Radon fan actively creates the vacuum and forces air to move into the system. Once there, it will be drawn away, above and beyond the house.

And that is the next question: what does the fan do?

The fan is the active part in that system, and there are different types of fans that can draw a lot of air by volume. 

Then why does the system have to reach beyond the house?

Because wind and air movements can bring the Radon gas back into the house through an open window.

(Sometimes...) We have a situation with high Radon levels in a slab-on-grade-house (there is no basement or crawlspace). Do you have to drill a hole in the slab? Where would you do that?

Good question! This is a common situation. Very often I access the sub-slab aggregate (the gravel layer beneath the floor) from outside. By drilling through the footer, below the floor level, I can access the gravel layer and install my pipe and fan. All this is done without going into the house. From inside one has to find a closet or utility space where a suction hole and pipe can fit.  

Are the fans noisy?

No they are not, they're usually less noisy than the AC unit outside, although I have not measured it in decibels. I always try to install the fan away from bedrooms. What you sometimes hear is the airflow coming from the pipe. If possible we install the fan in the Attic, or outside, or above the garage.

.. and why does a fan have to be outside or in the Attic?

Because the rubber couplings that are connected to the fan may dry rot and leek, and nobody will notice it.  So therefore it's safer to have the fans outside or in the Attic above Living Spaces.

Is it possible that a fan can draw from the ground surrounding the house and into the basement, actually increasing the radon levels?

I never thought of it that way and I don't think it's possible because the house has a footer that is 2ft. deeper, a foundation, and the fans are not that strong! They create a vacuum at the spot below the slab, which allows air to move towards it, but they are not powerful enough to draw radon in from the perimeter outside the house and penetrate the footer.

Another question is: what about costs and maintenance?

There is no maintenance to the system, except for regular testing every three to five years. The electrical bill is that of a 75 Watt light bulb. There's a visual design, the manometer in the basement, which tells you that the system is working.  This shows the airflow (not a measurement of Radon).

90% of the fans that were installed 15 years ago are still running today. I have not replaced a fan that I installed in the last 4 years. They are very reliable. I use fans exclusively from one company; their products and customer service is outstanding.

Is there any difference between interior and exterior installation?

The price tag! Interior installations are more labor intensive. For example, you are hiding the pipe in a shelf closet and cut holes in each board that lines up perfectly with the one above and below. Then there holes in the floor (hard wood or carpet) and the ceiling, on each story, that have to fit precisely.... and the roof with proper flashing. This usually amounts to $150 additional costs.

The advantage? The system completely disappears (except for the exhaust vent). The interior installation adds to the resale value of the house in the future.

Do ceiling fans and humidifiers help to reduce Radon in your home?

No they don't, and even your sophisticated and expensive air filters cannot filter out radon gas. They an ineffective in reducing Radon.

The cost of the system?

It is usually around $1,100 to $1,400 with re-testing. This is a one-time investment for your lifetime, then you don't need to think about it anymore. In case you sell your home again, you will have no problem - on the contrary, your house is better off than other homes without a system. Radon is not going away, and awareness of Radon is increasing. People will not buy your home when it has high radon levels. It may be smarter to install the system now and have the benefit of it while you live there. 

Most jobs can be completed in a day.