State Laws Addressing Radon, Mold and Secondhand Smoke
Colorado
Colorado law was revised in 2023 to establish certain requirements regarding radon in rental housing. See Colorado S.B. 23-206; Colorado Rev. Stat. sec. 38-12-803.
Radon Disclosure and Warning. Colorado law requires that, before signing a residential lease, a landlord must provide the tenant a state-approved radon brochure, disclose any knowledge of radon levels in the property (including testing and mitigation records), and provide the tenant a written warning statement as specified in the law. The warning statement, which the tenant must sign to acknowledge receipt, includes the state recommendation that all tenants have a radon test performed before leasing and that elevated levels be mitigated.
Tenant Remedies. The states that failure to comply with these requirements constitutes a breach of the warranty of habitability. The law also provides that the tenant may void a lease and vacate the premises if the landlord fails to provide the written information specified in the law or make a “reasonable effort to mitigation radon” within 180 days of being notified of professional testing that reveals levels over 4 pCi/L. After January 1, 2026, this tenant remedy applies only to lease agreements longer than one year in duration.