Just to kind of mirror what the poster you're replying to said, it is "unlikely" you could use this to accurately detect radon. This article[0] talks about some of the difficulties you may face and how much data you'd need to collect.

Considering how inexpensive and reliable radon test kits are, it may be advisable to stick to that.

[0] http://www.azomining.com/Article.aspx?ArticleID=192