Radon Cheat Sheet

At Greenwood Estates Realty, we’ve been dealing with radon in real estate transactions for a combined 15+ years. Here are some tips we’ve learned over that time. As always, if you ever have a question about radon, let us know.


Radon Basics 1. Radon is a soil gas that enters the home from beneath and can cause lung cancer

2. Radon is common in Colorado and about 50% of homes have “elevated” radon levels 3. We recommend buyers get their home tested by an AARST/NRPP testing company, especially if the home has a basement 4. For detailed guidance on radon, visit this website

What is Radon?

Radon is a radioactive gas that enters homes through the soil beneath. Long term exposure to radon in homes can cause lung cancer.


Radon is the 2nd leading cause of lung cancer in the U.S. Like oxygen, radon is colorless and odorless.


Radon is present in Colorado – Every Colorado county is in EPA zone level one, which means every home has a decent possibility of high radon.


But don’t be afraid – Radon is common and any house can be fixed. Most houses can be fixed for about $1,000. It’s never a reason to not buy a house. Repeat, the presence of radon in a home is common and NOT a reason to forego a home purchase.


Is there a safe level of radon? Radon is measured in “picocuries per liter of air.” We commonly say “picocuries”. The current EPA recommendation is to fix houses that measure 4 picocuries and above.


How long does it take to test a house? – The minimum test duration is 48 hours. The doors and windows in the house should be closed for the duration of the test period and testing equipment should be left alone by the home’s occupants.


Measurement cost? A professional test costs $150-$200.


Can I use a DIY kit from Home Depot? – Technically yes, but practically no. Hardware store test kits work great but their laboratory turnaround time is usually longer than the inspection contingency period. Also, the test result won’t have professional credibility so it will be challenged by the seller. Professional testing companies use electronic equipment that provides credible, immediate results.


What if the house has a mitigation system already? – It’s not a bad idea to still test unless it’s been measured in the last year or two. Inspectors see many radon systems that visually appeared to be working but weren’t effectively mitigating radon to “safe” levels.


Radon Myths:

The house was closed up for a long time before the test, the test result is going to be skewed high and not valid.

False. Radon levels in the home reach a steady level after only a couple days so a house that has only recently been closed up will test close to the same as if it was shuttered for months.


My neighbor’s house has high radon, mine will too.

Not necessarily. Every house foundation is unique. Measure the house before paying for a mitigation system.