Short Term Radon Test Results

Previously I wrote that I was testing my house for radon. I got the test results back this week, and the test results came back as an average radon level of 2.9 pCi/L. The good news is this is less than the 4 pCi/L action level. The bad news is this is still elevated above average house level of 1.3 pCi/L. This test involved collecting radon over four days. At work, I am currently working on a project that involves looking at the indoor air variability due to radon or volatile organic compounds intrusion from the soil and groundwater. Thus, I know better than most how variable indoor air concentrations can be. They can vary a lot. Therefore, before deciding what to do, I have considered the following items:

• The test was done in winter under proper closed house conditions. Closed house conditions means keeping the doors and windows closed except for normal entering and exiting the house through the doors. This is not an issue in the winter because it is cold. This is also one of the reasons winter is one of the best time to perform the test, but it also means that the test will lead to higher results than if more open house conditions are maintained. When the weather is nice, I like to open the windows and doors, so that would generally mean at least during those times, the radon concentrations in my house should be much lower.
• The test was performed over four days. As I stated, indoor air concentrations can vary a lot, and in terms of those fluctuations, four days is relatively short term. Even ignoring the seasonal effect of closed versus open house conditions, the long term average radon conditions could be much higher or lower than 2.9 pCi/L. The reasons are not fully understood, but exterior temperatures and precipitation can affect it. A long term test over several months or even better a year, will give a much better understanding of the average concentration. If the results had been 1.3 pCi/L or less, than given the conditions, I would probably not be at all worried that the long term concentrations would be higher.
• The EPA recommends that the test be performed in lowest habitable portion of the house. As such, I placed the test in the guest room for that and other reasons stated previously. However, I am almost never in the guest room. I don’t have guests that often, and the door to that room remains shut most of the time. Thus the only air exchange in the room is via the ventilation ducts and a little underneath the door. Furthermore, my bedroom and all the common areas of the house (kitchen, living room, etc.) where I spend most of my time are upstairs and should have lower radon concentrations than the guest room. Therefore, even if the results from the guest room do accurately represent average radon concentrations, they are borderline for taking mitigation action and probably represent the highest levels in the house. While I don’t want to expose my guests to undue risks, especially since my guests are generally people I like or love, do I want to mitigate based on the results from this room?
• Finally, I’m a scientist, and I believe in validation and replication. This was one test result, and home test kits are generally not considered the gold-standard of any type of test. There is no doubt at least of some amount of inaccuracy with it.

Therefore, I have decided to test the house again, but this time for a longer duration. I have also decided to run two tests simultaneously. I plan to place two testers in the house, one in the guest room again and one upstairs in my master bedroom. I have ordered a long term home test kit that can be used to test between 90 and 365 days. I plan to run the test over an entire year to get a much better indication of what the long term average radon concentrations are in the house. Also, by testing both the guest room and master bedroom, I can better understand what my average exposure is both in terms of the average annual concentration and in the rooms where I spend the vast majority of my time. I will also add that while the guest room is a guest room now, as it is bedroom, legally and real estate-wise speaking, and thus in the future it could be a normal bedroom if my life changes or if I sell the house. Therefore I still consider it important to know what the long term radon concentrations are.

Check back in a year, and I will let you know what happened and how I am proceeding.