How can a radon test show 2.4 a couple of months ago and now shows 30?

Question

During the contract period on a home purchase we had a 3 day radon test done by a professional back in 09/2006. The test showed that the radon was at 2.4 piC/L. We bought the home and had another short-term test done two weeks ago (we had an extra mail-in test kit and were curious). This test shows the level at 30! Do radon levels vary this much or is it more likely that one of the tests is in error? In October, we did have a bathroom put into the basement which required some concrete work to run the drain line. Can this be the reason? We are getting another test done to confirm the level but are very concerned that someone may have tampered with the initial test before we bought the home (the home was occupied by the sellers at that time). Thanks.

Answer 1

There are two distinct possibilities. The first test may have been erroneous. It has been my experience that with household gasses very few testers take it very seriously. I recently had firemen in my house testing for CO and natural gas. They turned on their handheld units, and they immediately squealed, then started ticking very rapidly.

I know how those devices work, and I commented that they were getting a reading. The firemen exchanged weary, knowing glances with one another and tried to talk to me like I knew nothing. "They always do that..." When I asked to look at the meters they refused to let me.

The next day I had an independent tester come in and he read tagged our oven as hazardous. The firemen were getting a reading and lying! If firemen, who are supposed to protect us can't take this kind of thing seriously, who can you trust? Just because you pay a professional doesn't mean they'll be any more thorough. Sounds cynical, but I see it that way now.

The other factor is that the early testing may have been done when the windows were open. If your house has been winterized and the air isn't moving that will boost the reading. But by the amount you mention, I suspect it may be a combination of these two factors.

Answer 2

DH -- If the first test was done by a professional, and the second test was done by you (and please take no offense) then most likely your test may not be valid. There are many testing protocals a professional must follow which you may be unaware.

However -- It is impertive that you get a follow-on test done right away. Even if your Radon level is above 10 piC/L, this requires remediation. Check this website below for a NEHA certified provider near you. Ask for a CRM test, which is a short term test that can provide you with an imediate answer.

Other posters are correct when they say Radon Levels go up in the winter, at night, and after construction. In fact, a new source may probably be the air coming through the orifice caused by the new drain.

And please understand that if a professional had two tests of 2.4 piC/L and 30 piC/L, he would have to invalidate the test because it fell outside statical levels of confience (i.e. most likely an error).

In my experience, the highest I've seen a false reading was 40 piC/L because the homeowner tested too close to the furnace and didn't maintain closed house conditions.

Feel free to ask me more questions from my website at www.honorbuilders.com

Answer 3

Radon is usually evident in basements with dirt floors. More than likely, if your concret project involved digging up the floor and exposed ground...you may have had Radon come up into your basement. Air out the basement before you run another test...and then after a little while do another. Keep records of the tests. If you didn't dig up the floor...I would talk to a lawyer and see what they suggest and options you may be able to take. Because I know you would not have purchased the home if you knew the Radon levels were that high.

Answer 4

I would expect that a professional would test the air outside of the house and than test the indoor air. During certain weather conditions the levels of radon will increase over large areas, this would be the "background" reading. The difference between the two reading would indicate the levels of radon being giving off by the materials in the house. A whole house vent fan may reduce the levels.

Answer 5

First, radon levels ALWAYS go up in the winter -- in the warmer months windows and doors are open more often, allowing airflow to carry the radon out of the house. In the winter, homes are usually shut up tight most of the time, allowing the radon to accumulate.

And yes, the concrete in the basement is probably a new source (new concrete always is). I'm betting that if you test again in the late spring or early summer, the levels will go down again.