What Makes Radon Levels High?

Overview of the basics

Radon is the leading cause of lung cancer in non-smokers in the U.S. and is responsible for roughly 21,000 lung cancer deaths yearly. It is a colorless, odorless, naturally occurring radioactive gas that is made in the soil from decaying uranium. The decay process of those elements is very slow, so the production of radon gas in the earth and soil is constant and won’t stop in any of our lifetimes. Because of this, radon gas is constantly escaping from the soil below into the air above. 

If radon gas was orange (it is not), we would be able to see it coming out of the ground everywhere where there is uranium and radium in the soil. We would see orange gas coming up through the bottoms/foundations of our homes, and we would see it coming from fields, yards, streets, sidewalks, mountains, etc.

As a result, all of the air we breathe has radon gas in it. According to the EPA, the national  average concentration of radon in outdoor air is 0.4 pCi/L. While technically no radon is “safe”, 0.4 pCi/L is not considered a “high” or “actionable” concentration of radon. The national average concentration of radon in indoor air is 1.3 pCi/L, which is obviously higher and therefore “less safe” than outdoor radon levels, but is still nonetheless not considered “high” or “actionable”. 

Regarding radon in your home, because there is no known “safe” level of radon the EPA recommends that homeowners start considering action to reduce radon at 2.0 pCi/L.  On the other hand, the World Health Organization (WHO) has an action level of 2.7 pCi/L.  Regardless of which organization’s recommendation you choose to follow, one thing is certain: we want to expose ourselves to as little radioactive gas as possible.

What factors affect how high the radon levels are in a home? 

The million dollar question is: How much uranium is in the soil beneath the home? Decaying uranium (or its byproducts) is the source of radon gas. If there is no uranium at all in the soil below or near a house, that house wouldn’t have radon gas in it. It is really that simple. The opposite therefore is also true. If there is a high amount of uranium in the soil below a house, that house has a good chance of having an elevated radon level.

Assuming that there is a source of radon in the soil below a home, there are other factors that affect how high the radon concentration is:  

• How porous/permeable is the soil below the home? For example, radon gas travels more easily through gravel than clay to get into a house. That said, radon gas still travels through clay pretty easily so this won’t make or break whether there is radon in a home.
• What time of year is it? The driving force that brings radon from deep in the soil into a home is a pressure difference between the soil and the home. More negative pressure in a home = more aggressive pull on the soil gasses = higher radon levels. The pressures in homes will change with different seasons/conditions/weather patterns. 
• What is the ventilation rate of the home? Homes these days are being built more and more “airtight” to improve energy efficiency, but making homes more airtight can trap more radon gas into the home. It is like plugging a sink with the water on - radon gas keeps coming in and it can’t “drain out (air out)” fast enough - so the concentration rises. That said, the ventilation rate again doesn’t make or break if there is a high level of radon in the home, it is just one of the many variables that play a role.

How do you fix high radon?

Installing a radon mitigation system is the only permanent and cost effective solution to high radon. It typically consists of a 3 to 4 inch PVC pipe that runs from the soil beneath the home’s foundation up to the roof. There is a continuously running suction motor called a radon fan on the pipe. The fan should be mounted on the pipe in the attic or on the outside of a home, depending on what route the pipe takes to the roof. 

The system is designed to continuously draw radon from the soil beneath a home, and safely vent it above the roofline per building code. It is designed to stop most of the radon in the soil from entering the home in the first place; it is not trying to “suck the radon out of the house”. Once a system is installed, the radon levels should be retested to verify that the radon level has reduced sufficiently.

Summary

The only way to know if a home has high radon is to do a radon test.  The only cost effective and guaranteed way to fix a home with high radon is to install a mitigation system(s). Radon induced lung cancer is preventable when people take the proper action to test and fix the home early on. If you haven’t tested your home, or if your home has high radon but you haven’t yet fixed it, take action today!