 Measurements over 10 pCi/L warrant only another short term test so that abatement measures are not unduly delayed.Purchasers of real estate are advised to delay or decline a purchase if the seller has not successfully abated radon to 4 pCi/L or less.Because the half-life of radon is only 3.8 days, removing or isolating the source will greatly reduce the hazard within a few weeks.