Map of Radon gas levels in Portland, OR

Understanding Radon Gas as a Portland Home Buyer

Checking for Radon Gas as a Portland Home Buyer

The Oregon Health Authority released new information that confirmed long-held suspicions about the soil in Portland: it releases higher levels of radon gas than average.

According to the EPA, about 6% of homes in the US have elevated radon levels. However, in Portland, testing has revealed that 28% of homes have high levels of radon. Radon is a gas that is invisible, odorless, and radioactive. It is the second-leading cause of lung cancer in the country. The gas seeps out of the ground and enters homes and buildings through foundations and walls.
But what is the reason behind Portland’s high radon levels? The answer lies in events that occurred millions of years ago.

During a series of floods known as the Missoula floods, billions of gallons of water flowed from what is now western Montana into eastern Washington and then down into Oregon’s Willamette Valley. Within the rocks and boulders carried by the water were traces of uranium. Today, Portland is built on top of these rocks, and the uranium continues to decay into radium, which further breaks down into radon gas.

In recent years, the Radon Awareness Program of the Oregon Health Authority has been gathering data on radon levels in homes throughout the state.

It is important to note that the EPA advises mitigation when radon levels reach 4 pCi/L or above, although any level of radon is considered unsafe. In recent home tests conducted in the Portland area, some results showed levels as high as 128 pCi/L.

The OHA has created a Radon Risk Map for Oregon, which assigns a color to each zip code based on the level of risk. In Portland, there are 11 zip codes labeled as red, indicating a “high risk” of radon. 18 zip codes are labeled yellow, representing a “moderate” risk, and 4 zip codes are green, indicating a low risk. However, homeowners should not feel completely safe just because they reside in a “green” area, nor should they panic if their zip code falls in the red zone (which is the case for most of Northeast Portland, by the way).

Click here to see a list of all Oregon zip codes and their Radon risk levels.

While risk assessment maps are useful, it is important to understand that the nature of radioactive rocks is inherently unstable. An area that did not have radon emissions a decade ago may have them now, or vice versa. Additionally, radon levels can vary from one home to another depending on factors such as construction type and heating, ventilation, and air conditioning systems. Weather and season can also impact radon levels, with higher levels typically seen during winter.

Thinking about getting your house checked for radon? At we refer to the best inspectors who give you an independent radon report. The report will include suggestions on what steps to take if radon levels are found to be 4 pCi/L or higher.

What is Radon Gas?

Radon gas is a colorless, odorless gas that is produced naturally through the breakdown of uranium in rock, soil, and water. When radon gas is released into the air, it can easily enter buildings through cracks in the foundation, walls, and floors.

Why is Radon Dangerous?

Radon gas is the second leading cause of lung cancer after smoking and is responsible for about 21,000 lung cancer deaths each year. The danger arises from the fact that radon gas is radioactive and over time, exposure to high levels of radon can damage lung tissue and cause cancer.

How is Radon Measured?

Radon is measured in units of picocuries per liter of air (pCi/L). The U.S. Environmental Protection Agency (EPA) has set the action level for radon at 4.0 pCi/L. This means that if the radon level in your home is at or above 4.0 pCi/L, it is recommended that you take action to reduce the radon level.

How to Check for Radon Gas?

As a Portland home buyer, it is important to have the property tested for radon gas before purchasing. The most accurate way to test for radon gas is by a professional radon testing company. A radon test involves leaving a testing device in the lowest level of the home for a period of time, usually 2 to 7 days, depending on the type of test. After the testing period, the device is collected and the results are analyzed.

Another option is a do-it-yourself radon test kit, which can be purchased at most hardware stores. These kits come with instructions on how to conduct the test and then send the sample to a lab for analysis. However, it is important to note that these kits are not as accurate as professional testing.

What to do if Radon Levels are High?

If high levels of radon are detected, the EPA recommends that homeowners hire a certified radon mitigation contractor to fix the problem. There are several methods for reducing radon levels, including installing a radon reduction system, sealing foundation cracks, and increasing ventilation.


In conclusion, as a home buyer, it is important to ensure the overall safety of the property before making a purchase. The main safety concern when it comes to the indoor air quality of a home is radon gas, which can easily enter buildings through cracks in the foundation, walls, and floors. As such, it is highly recommended that buyers have the property tested for radon gas before making the final decision to buy.

At we help you navigate all the potential pitfalls of buying a home and  when representing buyers, we often help you put the cost of a mitigation system onto the seller.

Contact us today to get started!


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Harlan Mayer

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Harlan Mayer, Owner and Principal Broker
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About Our Brokerage: is a local Portland brokerage with over 20 years experience that is designed to help our clients build wealth and improves their lifestyle. We are prospecting and negotiation experts, and work towards trusting and  long-term relationships with our clients.

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