Illinois revised its radon disclosure law to incorporate disclosure requirements for radon in rental housing. Illinois Comp. Statutes Chap. 420, §46/25 . The law does not require testing, but establishes a landlord's duty to disclose known elevated radon levels in certain circumstances.
Duty to Disclose. Under the law, landlords must notify current and prospective tenants of a dwelling unit about any radon hazard revealed by the landlord's testing of that unit. The law also requires landlords to disclose to prospective tenants of a residential unit any radon hazard revealed by the current tenants' testing of that unit, unless the landlord's subsequent testing demonstrates that a hazard does not exist. The disclosure requirements apply only to dwelling units located below the third story above ground level.
The landlord is not required to provide this disclosure if the landlord has undertaken mitigation activities and a subsequent radon test indicates that a hazard does not exist in the dwelling unit.
The disclosure law defines "radon hazard" as "exposure to indoor radon concentrations at or in excess of" the recommended action level of the U.S. EPA or the Illinois Emergency Management Agency. 420 Il. Comp. Stat. § 420, 46/5.