i believe Bob Wood from Mr. Radon has done this before with a stage smoke machine on a very large slab. I am pretty sure its an item that can be rented (although not exactly for its intended purpose). Just look for the smoke where there may be any leaks.............

Bob Wood might be sleeping, but i couldn't resist. I think that when we, as Canadians, developed our mitigation guidelines, we had the benefit of learning from our southern neighbors successes and failures. I can certainly see why the EPA would be overly cautious when developing their original standards, but technology certainly has changed as have material standards since the original US standards were implemented.

I know that Health Canada did extensive testing before giving the thumbs up to sidewall discharge. Personally, i am with Rob on this one. I haven't had any issues with re-entrainment with sidewall discharge. That being said, we also are not allowed to use anything less than sched 40 pipe and fittings or fans that are not certified for use indoors (must be sealed).

In cold climates, the outdoor fan and piping simply isn't an option for most houses (for many reasons, cost, esthetics, not to mention freeze-ups). We want more people to have these systems installed, so we have to make it more practical for it to be implemented. If i told all my clients that i had to run the pipe above the roof line, 90% would likely tell me to hit the road (simply because it would mean running the pipe through most of their living space; cannot run outside due to freeze-ups). Not to mention the costs would be prohibitive to many middle class working families.

Obviously, we don't discharge the system in areas where people gather outside (kids sandbox, decks etc). Not just because of radiation levels, but also because of the fan noise. We don't want people to turn these systems off because its bothering them.

I really think its time the EPA looked into changing their guidelines. It might encourage more people to test/mitigate as well as reduce mitigation costs. Especially in colder climates like Minnesota.