Went through this last year when selling my house. The buyer's wanted it checked "just to know", and their engineer told me the level allowed was 2 and under. He instructed me to NOT open any windows or doors prior and during the test. Reading came back at 5.4 and everyone went crazy including my wife. Now because I had a realtor I had to remedy the situation before it could be sold.
Mistake #1 was not airing out the basement before the test.
Mistake #2 was 4 was the acceptable level or below not 2.
So at a cost of appro. $1800 I had to install a system (I opted for a larger fan than recommended) before the sale and re-test.
Now system test came back at almost nil. and installers told me if I wasn't misinformed by the buyer's engineer and aired my basement out prior to first test I would have passed fine.
***note also basements with french drains will alter the results also.
Ron
Well, of course "airing out the basement" will give you a low reading. You are basically doing what the exhaust fan will do--letting any Radon outside.
But unless you plan on leaving your basement windows open year round, that number means nothing.
