Reducing Radon Levels

If you've tested your home for radon and found elevated radon levels (levels greater than 4 picocuries per liter-4 pCi/l), and if you've confirmed those levels with a follow-up test, it is recommended that you take action to reduce your exposure.  This may mean simply changing your occupancy patterns (spending less time in the basement if levels down there exceed the guideline but levels on the first floor are acceptable), or taking action to prevent or reduce radon entry.  As a general rule, it's probably better to try to reduce the radon level, and then you won't have to worry about where you spend your time in your home.


The most common technique for reducing exposure is to prevent or reduce radon entry.  This can sometimes be achieved by caulking and sealing entry points such as the floor/wall joint; sump openings; cracks in the floor or walls; space around plumbing, wiring or ductwork; or openings at the top of a hollow block wall.  Unfortunately, caulking and sealing is rarely adequate as a stand-alone reduction technique, though it does sometimes work when the radon levels are only marginally elevated.


To achieve guaranteed results, a trained contractor should be hired to install a radon mitigation (reduction) system.  Almost any radon level, regardless of how high it is, can be brought down to below 4 pCi/l.  The most common technique used in Michigan is active soil depressurization (ASD).  This reduction method involves reducing the pressure under the house so radon isn't being pushed in through openings in the foundation floor or walls.


ASD systems are fairly simple.  They start with a four-inch PVC pipe that goes down through the foundation floor and runs up and out of the house.  A small in-line fan is attached to draw suction from under the slab, and additional PVC extends from the top of the fan to above the eave of the roof.  (This allows the radon to be exhausted in an area where it can be quickly dispersed and diluted by the atmosphere and won't be drawn back into the house through doors, windows, or other openings.)


ASD systems can utilize many different suction options.  Sometimes the contractor will take advantage of an existing sump opening, fit it with a special cover, and run the PVC pipe down into that hole.  Other times he/she might drill a four-inch hole through the cement and dig out a pit about the size of a five-gallon pail, or they might try to tie into an existing drain tile.  When dealing with a crawlspace, a vapor barrier would be used in place of the cement floor, and suction would be drawn from under the plastic/polyethylene sheet.


Though both of the above diagrams show the system going up through the house, it is actually quite common for the pipe to exit the house just above ground level.  The fan is mounted on a 90-degree elbow, and the exhaust stack runs up the side or back of the house.  The diagram at right shows such a system with the suction point being the sump opening.


Nationally the price of a radon mitigation system ranges from approximately $500 to $2,500, but here in Michigan they generally cost between $750 and $1,500, depending on where you are in the state and who you hire.  The systems can usually be installed in a day or less, and a reputable contractor will provide a guarantee that he/she will achieve results below 4 pCi/l.  Often the systems are so successful that they actually achieve results below 2 pCi/l.


The Michigan Department of Environmental Quality does not license or otherwise regulate radon mitigation contractors, and though it is not required in this state, it is suggested that you use trained and certified individuals when contracting for radon reduction services.  There are currently two national organizations (the National Radon Safety Board and the National Environmental Health Association) that offer certification for testers and mitigators.  Lists from these organizations are available on their websites ( and or they can be obtained from your local health department, or by calling the Michigan Department of Environmental Quality Indoor Radon Program at 800-RADON GAS/800-723-6642.