The EPA has recommended mitigation actions definitely be taken when radon,
as measured by its radioactive decay, exceeds 4 pico-Curies per hour per liter
of air (4 pCi/hr/l). Consideration of mitigation actions is recommended at
2 pCi/hr/l. Some 34 states have also put
in place various regulations. These mainly relate to testing upon the pending sale
of real estate (and civil and criminal penalties for non-disclosure) and mandatory testing in schools and certain civic buildings. The EPA has compiled a convenient guide to state-by-state resources on radon.
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