The Montgomery County Code amended required radon testing and mitigation in specific rental units on July 1, 2023. The City of Rockville has also adopted a radon bill (see second link below). Radon testing is only required for the following rental units: ground floor and basement units in single- family homes, multifamily apartments, and condominiums. Landlords must conduct a radon test before leasing a unit to a prospective tenant, within three years before the date of the lease. The landlord is responsible for the cost of testing and must provide the tenant with certification that the test verifies radon below 4 pCi/L, the EPAs recommended action level.

Tenants may at any time during their tenancy (at their expense), conduct a radon test or hire a professional to test a dwelling. If test results indicate a radon hazard at a level 4 pCi/L or higher, the tenant must notify the landlord in writing within 14 days and provide a copy of the test results. The landlord must perform a follow up test in accordance with EPA standards. Within 90 days after a confirmed test, the landlord must mitigate the premises to reduce radon below the action level of 4 pCi/L and provide the tenant with a final copy of third-party professional test results.

If the landlord fails to mitigate, the tenant may terminate a lease without loss of security deposit or any other financial penalty. If exercising this option, the tenant must provide in writing to the landlord, a notice of intent to terminate and vacate premises. The notice may be effective either immediately upon receipt by the landlord, or as agreed upon by both parties, to allow the tenant time to find alternative housing. Online users may contact the Office of Landlord Tenant Affairs by submitting a service request. Click "Create Service Request" .