Montgomery County Rental Radon Requirements

The County states that its requirements apply to ground-contact or basement units of residential rentals in single-family homes or multifamily dwellings, including condominiums. The County also describes the requirements as applying to multifamily and single-family rental housing.

The effective date listed in the County’s enacted Bill 26-22 materials is July 1, 2023.

County housing guidance states that a landlord must have a radon test performed within three years before leasing a unit to a prospective tenant, and that the landlord is responsible for testing cost.

For new leases and lease renewals, the County describes providing test-result information and required lease certification or addendum materials. Use the current County page and sample addendum rather than a generic form.

County/DHCA guidance identifies 4 pCi/L as the action level. An existing tenant with a result at or above that level must notify the landlord in writing and provide the result within 14 days. Within 14 days after notice, the guidance says the landlord must hire a licensed radon professional to retest and confirm the result.

After a confirmed elevated result, the County guidance provides 90 days to mitigate the unit below 4 pCi/L and requires disclosure of the final third-party professional results. The guidance also describes lease-termination protection when a landlord does not mitigate as required. Review the current County materials or seek legal or housing advice for a compliance question.