Real Estate Transactions

Understanding radon: A home buyer and seller's comprehensive guide

What radon is, why it matters for buyers and sellers and how to manage it in real estate transactions

Radon and Smoking: A Dangerous Combination. If you live in a home with high radon levels, smoking raises your risk of lung cancer by 10 times. Learn more by calling the National Radon Hotline: 1-800-SOS-RADON. (1-800-767-7236).

Published on

November 9, 2023


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Radon, sometimes referred to as a “silent threat,” is a critical but often overlooked consideration during home sale transactions. 

Radon is a colorless, odorless, and tasteless gas that can seep into homes and pose serious, potentially deadly, health risks. 

When a home is being sold, radon tests are often performed, though it is not required to complete a radon test for a real estate transaction in Connecticut. 

This leaves both buyers and sellers asking whether they should test radon — what’s the risk, what’s the cost, and what happens if radon is detected?

In this article, we will explore what radon is, why it matters for both buyers and sellers and how to manage radon-related issues in real estate transactions.

What is radon?

Radon is a radioactive gas that forms naturally from the decay of uranium in soil, rock, and water. 

It's present in varying concentrations in the earth, and when it escapes from the ground, it can enter homes through cracks, gaps, and other openings in the foundation. 

Radon is especially prevalent in regions with higher levels of uranium in the soil.

What are the potential health risks of radon?

Exposure to radon gas can pose significant health risks, the most significant and well-established is lung cancer. 

Radon is the leading environmental cause of cancer and the second leading cause of lung cancer in the United States, following smoking. It is estimated to be responsible for thousands of lung cancer deaths each year. 

The EPA estimates that radon causes 21,000 deaths of cancer deaths in the U.S. each year, more deaths than caused by drunk driving (17,400) and home fires (2,800) annually.

The risk of developing radon-induced lung cancer depends on several factors, including the concentration of radon, the duration of exposure, and individual susceptibility. Long-term exposure to elevated radon levels significantly increases the risk. It's important to note that there is no safe level of radon exposure. 

The risk of lung cancer increases with higher radon concentrations. Even at low levels, radon exposure can contribute to the development of lung cancer over time.

Learn more about radon’s health impacts on the CDC website

Radon levels in Connecticut homes

Radon levels can vary significantly from one house to another, even within the same neighborhood. 

The risk of elevated radon levels in homes is closely linked to geological factors. Connecticut has a mix of geological formations, including bedrock, which can contribute to radon issues. Areas with higher levels of uranium in the soil and rocks are more likely to have elevated radon levels.

Homeowners in Fairfield County should take extra precautions when assessing radon risk, as the county is considered to be in Zone 1 by the U.S. Environmental Protection Agency (EPA). Zone 1 is the highest potential for radon exposure, meaning there is a higher likelihood of elevated radon levels in homes in this zone. 

Among Connecticut towns, many in the Fairfield County area have been noted to have high levels on radon on average. Greenwich’s health department noted that the average indoor level of radon in the town was measured at 4.5 pCi/L or more, which is above the EPA's threshold of 4.0 pCi/L. 

Should I test for radon when buying or selling a home in Fairfield County?

As mentioned, testing for radon is not required by law in Connecticut to complete a real estate transaction. With that said, there are some factors to consider when deciding whether to test. 

The Residential Property Condition Disclosure Report also contains a section that informs the buyer of their right to conduct radon testing on the property. 

Though not required, sellers should consider testing for radon before listing. If elevated levels are detected, addressing the issue before listing can prevent potential buyers from walking away due to radon concerns. 

It's often more cost-effective for the seller to install a mitigation system. These can be installed to reduce radon levels to safe concentrations. This can be negotiated during the buying process, with the seller typically taking responsibility for installation and costs.

The Residential Property Condition Disclosure Report given to buyers contains a section that informs the buyer of their right to conduct radon testing on the property. 

Buyers should carefully review the disclosure report and, if necessary, request radon testing as part of their due diligence process. Keep in mind that sellers are only required to disclose what they are aware of, not test. 

Most buyers include radon testing as part of their due diligence process. Testing is relatively simple and can provide peace of mind. It is typically the buyer's responsibility to arrange and pay for the radon testing, unless otherwise negotiated.

How to get radon tested in Connecticut

Getting a radon test conducted in a home in Connecticut before buying is a straightforward process. 

You should make sure to work with certified radon measurement professionals and laboratories in Connecticut. You can find a list of qualified radon mitigation professionals on the Connecticut Department of Public Health's website

Once you schedule an appointment, the tests will be conducted using two primary methods: short-term tests and long-term tests.

Short-term tests, which are often used for real estate transactions, typically take a few days to a week and provide a snapshot of radon levels. Long-term tests, which last for 90 days to a year, provide a more extended evaluation of radon levels. They are useful for ongoing radon monitoring.

The radon testing professional will place a radon testing device, such as a charcoal canister or an alpha-track detector, in the lowest livable area of the home, such as the basement or first floor. 

What is the cost of radon testing in Connecticut? 

The cost of radon testing in Connecticut can vary depending on several factors, including the type of test, the location, and the specific service provider you choose. 

If you’re already getting a home inspection performed as part of your transaction, typically you can add a short-term radon test for a couple of hundred dollars. 

There are also DIY home radon test kits that can be purchased online or in department stores, typically priced between $15 and $40. Some local and state health agencies also make tests available for free for those who request one.

What happens if the house I’m purchasing has high radon levels?

The radon testing professional will analyze the test results and provide a report. If the radon levels are below the recommended action level (usually 4 picocuries per liter or pCi/L), no further action is needed.

If elevated radon levels are detected, you may want to negotiate with the seller regarding radon mitigation before completing the home purchase. A qualified radon mitigation professional can install a mitigation system to reduce radon levels. The terms of who pays for the mitigation and any potential credits or adjustments to the purchase price should be outlined in the negotiations.

The approximate cost of a radon mitigation system in Connecticut is $1,200, according to the state department of public health.

This system will include a vent pipe and fan that draws radon from beneath the home and releases it safely into the outdoor air. After the radon mitigation system is installed, it is advisable to conduct post-mitigation testing to ensure that radon levels have been effectively reduced to safe levels.


Radon may be a silent threat, but it's one that both home buyers and sellers should take seriously. 

Properly managing radon will ensure your closing is smooth and that your family is healthy. When it comes to radon, knowledge, testing, and professional guidance are your best allies.

About the author

Pederson Real Estate Law

Pederson Real Estate Law is a boutique law firm based in Greenwich, Connecticut. We provide experienced, efficient legal services for clients in residential real estate closings —purchases, sales, and refinances.