When home radon levels trend down, this generally means chimney effects are not strong . Indoor and outdoor air temperatures ( and thus pressuress ) may be more in balance , or barometric pressure is steady or rising indicative of nice or clearing weather . In addition
, perhaps chimney effects have not been strong enough to reestablish the normal radon levels in your home , allowing some of it to naturally decay in accordance with its 3.8-day half-life ( one half of radon present decays and disappearss every 3.8 days ).
It ’ s easy to “ over think ” what is going on. The important thing is to find a long-term average characteristic of your home and the way you use your home
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Ventilation behavior is important , but overriding factors are more likely to be the geology on which your home sits , its design , and methods of constructionn .
Geology can be checked versus the EPA ’ s maps . Important design factors are whether there is a basement , whether footprint is large , whether there are multiple storiess to createe stronger chimney effects , and the tightness of the building envelope ( often tighter in newer homes for improved energy efficiency).