Radon

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Under-slab ventilation. Just as a suction fan can be used to ventilate sump pumps or block walls, one (or more) fans can remove radon from beneath a concrete slab floor, as long as there's an adequately permeable gravel bed beneath the concrete. This approach is particularly good for new construction, since a labyrinth of perforated pipes can be laid under the slab.

Other Techniques

Ventilation. Indoor radon concentrations can be reduced by diluting the air in the house. The relationship is direct but nonlinear: If you double the air change rate, radon concentration will be cut by 50%; quadruple it, and the level will be cut by as much as 75%.

Because of the limitations of comfort and energy cost, ventilation without heat recovery is likely to be acceptable in only one form. If you're willing to seal off a crawlspace or basement from your living area, insulate the floor and ventilate the area below, you may achieve significant radon reductions inside the house.

Heat recovery ventilation (with an air-to-air heat exchanger) can be used to good effect in houses with low natural rates of air change. A typical 250 cfm unit, for example, could change the air in a 900-square-foot basement about twice per hour. If the original air change rate had been one-half per hour, that appliance would provide the ventilation. Radon in the basement (the major source leading to the house) would be reduced by 75%.

Outside air for appliances. Part of the depressurization inside a house (which draw radon into the building) is caused by appliances that use air. Examples include furnaces, woodstoves, water heaters, clothes dryers and exhaust fans. Though supplying these items with outside air directly may not reduce radon concentrations dramatically; doing so will have the additional benefit o1 making the house more comfortable.

Coping with hot water. Granulated, activated carbon water filters will readily remove radon. However, high rates of flow may overwhelm smaller residential filters. If a test turns up high radon levels in your water, you should probably look into a substantial whole-house system.

In the Meantime

There are also a few very simple — though not necessarily easy — things you can do to reduce the risk of radon. First, test different areas of the house; radon levels are seldom consistent throughout a building. Try to spend most of your time in the areas where radon concentrations are lowest. Second, smokers should either quit or move. Recent information suggests that radon may have a synergistic effect with cigarette smoke, increasing the risk greatly for smokers. In fact, Dr. Edward Martell of the National Center for Atmospheric Research is convinced that current EPA risk figures overestimate the hazard for nonsmokers by 600% and underestimate it for smokers — by 50%.

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