A few years ago our next door neighbors put their house up for sale, and found they needed to put in a radon mitigation system in order to sell the house. To make a long story short, we wound up having a radon pump installed too. We paid just under $1,000 for it. If you have to get one, have it put outside, some people have them installed in the basement or in closets, but when it's running it sounds like a dryer, just going on...and on...and on.... Fortunatly our radon level was actually quite low according to the guy who installed the system, it's just that it was a tad higher than "acceptable levels". He said most houses where he installed systems the radon level was close to 200X "acceptable levels".

There is another product out, and I've been trying to talk my DH into it. Our house is just above the water table, and though you can't say our floor is ever wet, it's always very humid down there and there are always marks on the floor whenever you move something that's been sitting in the same spot for several weeks. I found out about it when I was looking at concrete sealers online. This sealer is only sold for do it yourselfers online, otherwise you have to have it done by a company. It works to seal out water that's in the ground below the concrete basement floor, but it was designed to seal out radon, and from everything I read, it does a good job too. It's also rather expensive, but it's an option to the pump.

These are sites I saved when I was looking for info
http://www.vseal.com/101/concrete_sealer.php
http://www.wetsealers.net/products.html
http://www.stonetechnologiesinc.com/specials.html
http://www.concretesealers.com/
http://www.radonloc.com/faq.html
http://www.radonseal.com/
The product they all sell, from what I've seen, is the same formula.

Check you code for placement of the radon system. The new subdivision around here all have them inside - basement that is.

So the fans seem to work? I had been interested in the sealers as well because our basement developed some mildew after we moved in--but I read somewhere that they stop working and that you need to re-apply. Is this true?
I will check if there is a code for radon fans here.
Have you had your level checked since you had the fan installed?
The radon really bothers me. I hope that we haven't lived here long enough for it to have hurt the kids. We did not have our own agent when we bought our house and the seller's agent said "as a science teacher, I can tell you that you have nothing to worry about with radon. It is an odourless gas that cannot hurt you and I think you should save money and not get the test." We got the test, but the results came in after we had made an offer. He was obviously knew the level was high and was not working in our best interest (although he took the cut as if he had been our agent too.) I can't imagine that the New York Realtor's association would condone that kind of talk about radon.

The radon mitigation guy also assured me that I had nothing to get panicky about just because my numbers were lightly higher than the government levels allowed. Usually if someone is in the business to sell and install a product, he's going to keep telling you how important it is that you have it, especially if it's expensive. This guy didn't seem to think I was in any desperate need of it.
He even mentioned how many of us have lived our lives in homes just chock full of radon gas all our lives, and we've had a great survival rate.
I saw a map once that showed that I've been living in high radon areas for my whole life, and I'm 54 and don't personally know of anyone who's died of cancer, except for a couple of heavy smokers.
Don't stay up at night worrying about it. If you know you have a radon issue you should tend to it, but you don't have to rush into it. Check out your options, get information, and don't believe the worst of what you may read or hear.

When my sister discovered radon in her house, she moved.

Here is a plain language publication on radon risk and mitigation from EPA that should help with your confusion:

Here is a link that might be useful: EPA - Radon

We did,We had some sort of piping around foundation,we had fan on it too.It did work.

We did, in this house and the last. There are three pipes that go from under the basement floor to the basement ceiling, then out a wall. Outside there is a fan which is practically silent and the pipe goes to the height of the second story chimney. There are alot of homes here with systems. The ground has alot of rock in it. I believe radon is related to uranium levels. In the warm weather adequate ventilation helps. Read the EPA link that the other person gave you. Our level was around 12 and it went down to 2. Oh, any holes, drains or cracks in the basement floor will allow the radon gas to seep in.

Um, you realize you replied to a thread that is 12 years old?

Plus, local codes require mitigation systems, either passive or powered after sealing.

As a former Radiation and also Asbestos Worker, I agree with I pinkmountain!