The act requires a contract to sell residential real estate to contain, and a landlord of residential real estate to provide to prospective tenants, in writing:
A warning statement about the dangers of radon and the need for testing;
Any knowledge the seller or landlord has of the residential real property's radon concentrations and history, including tests performed, reports written, and mitigation conducted; and
The most recent brochure published by the department of public health and environment that provides advice about radon in real estate transactions.
If a landlord fails to provide the written disclosures or fails to mitigate an elevated radon level, the tenant may void the lease in accordance with the statutes governing the implied warranty of habitability; except that after January 1, 2026, the tenant may void the lease only if the lease is greater than one year in duration.
The real estate commission is required to promulgate rules requiring that these warnings and disclosures are made in real estate transactions that use a broker.
Colorado law requires a radon professional to be licensed. The act exempts a tenant from needing a license when the tenant is testing the property leased by the tenant.
APPROVED by Governor June 5, 2023
EFFECTIVE August 7, 2023
NOTE: This act was passed without a safety clause and takes effect 90 days after sine die. (Note: This summary applies to this bill as enacted.)

Statutes affected:
Preamended PA1 (04/05/2023): 12-165-107
Engrossed (04/13/2023): 38-12-503, 12-165-107
Reengrossed (04/14/2023): 38-12-503, 12-165-107
Revised (04/19/2023): 38-12-503, 12-165-107
Rerevised (04/21/2023): 38-12-503, 12-165-107
Final Act (04/27/2023): 38-12-503, 12-165-107
Signed Act (06/05/2023): 38-12-503, 12-165-107