Indoor Air Quality – Testing For Radon
Radon was one of the topics covered in the Indoor Air Quality class we took recently. We understand that the concentration of radon gasses that naturally come out from the soil various from region to region and in some cases from house to house. Our instructor, Rich Prill, Washington State University’s Extension Energy Program, mentioned that one of his clients found higher level of radon compared to the neighbor’s houses because there is a subterranean stream running under the client’s house some 10-20 feet below surface that affects the gas composition of the soil under the house. So, even if the radon zone map of California show that we are in a moderate area (predicted average indoor radon screening level between 2 and 4 pCi/L), we should test for it.
What is radon?
Radon is a noble gas that doesn’t react with anything else. It’s present in our soils, rocks and sometimes water. The problem with radon is that it has a 3.8 day half life during which it goes through radio active decay, releasing alpha particles that can cause lung damage. So, if you breathe in radon, which is a colorless and odorless gas, these large alpha particles can damage and mutate cells in lining of your lungs. Radon is the second leading cause of lung cancer after smoking.
So where does it come from? You’ve heard of uranium, right? Uranium 238 is the most prevalent naturally occurring radioactive material in the ground. It has a half life of 4,500,000,000 years. Uranium 238 eventually turns into radium 226, which has a half life of 1590 years. Then radium 226 turns into radon, which has a half life of 3.8 days. At this point you may ask, “What is half life?” Half life means the period of time after which only half the mass of the original radioactive element remains. So, suppose a radioactive material starts with 100% of a radioactive material, after a single span of its half-life only 50% of that radioactive material would remain. The other 50% of the material would have converted either into energy or another element which may or may not be radioactive.
Why do you want to test for it?
Radon is a colorless, odorless gas and it occurs naturally and it’s in our soil at different concentration. The gas comes out of the ground and it can get into your house if the floor is not airtight. Most houses with crawl space like ours is not airtight. We know it’s not airtight because we can smell the dampness and mold from the crawl space when it rains. So, if there is any radon in the ground, it would certainly get into the house. In fact, when it rains the water in the ground acts like a air and vapor barrier so any radon gasses in the ground would look for path of least resistance, or dry soil to release. The dry area happens to be under the house so when it rains the crawl space may have extra concentration of radon.
The testing result could be different from day to day, depending on the season, rain and stack effect.
EPA gathers data from the various testing conducted by labs and publishes results (aggregated by zip codes) on a map. California Department of Health publishes a report that lists the number of tests conducted in a given zipcode as well as the number of tests that resulted in level above the EPA threshold of 4pCi/L. You can find the PDF here.
So, I just bought some short term radon test kits at the neighborhood hardware store and will test the house. If the results show a level higher than 4pCi/L then we would take measures to mitigate it by putting in a pipe under the plastic sheet used for sealing off the crawl space and venting it to the outside. You can find a PDF of radon resistant construction here.
UPDATE: Our result for the short term (96-hour) Radon test was .2pCi/L, which is quite low!
About the Author
Chie is one of the co-creator of Midori Haus. When she is not sharing her stories of transforming an old house and giving tours, she enjoys trail running and hiking.