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Montgomery County Maryland Radon Testing Law

As of October 1, 2016, County law requires that "a single-family home located in the County must be tested for radon before completing a sale of the home."  This requirement is contained in Chapter 40 of the County Code, as amended by County Bill 31-15.


Where Does the Law Apply?

The radon testing requirement applies throughout the County, except in the Town of Barnesville, the City of Rockville, the Town of Kensington, and the Town of Poolesville.


What Homes Must Be Tested?

The law requires the testing of single-family homes, which includes detached single family homes and townhomes, except those units that are part of a condominium regime or a cooperative housing corporation.  In addition, the law does not apply if the sale of the home is:


  -Exempt from the transfer tax under Md. Tax-Property Code, §13-207, as amended;

  -By a lender or an affiliate or subsidiary of a lender that acquired the home by foreclosure or  deed in lieu of foreclosure;

  -A sheriff's sale, tax sale, or sale by foreclosure, partition, or by court appointed trustee;

  -A transfer by a fiduciary in the course of the administration of a decedent's estate, guardianship, conservatorship, or trust; or

  -A transfer of a home to be converted by the buyer into a use other than residential or to be demolished. Home must be tested even if buyer does not want the test.


Who Must Do the Radon Test?

The law requires the seller to perform the radon test, or permit the buyer to perform the radon test.  If the seller offers the buyer the opportunity to do the test, and the buyer chooses not to, the seller must perform the test to meet the statutory requirement that a test be performed.  Both the seller and the buyer must receive a copy of the results of the radon test.


The test may be done by the seller, buyer, or third party (for example a home inspector or radon testing professional) using an approved testing device.


When Must the Test Be Performed?

A radon test must be done within a year of the settlement date in order to comply with the law. The test must be done with an approved testing device.


Which Testing Devices Can Be Used?

The radon test must be done using a testing device approved for use by the Montgomery County Department of Environmental Protection (DEP).  Each device has its own directions that must be followed to ensure accurate results.


Devices approved for use by DEP include:

  -Any test device included on the list of approved devices found on the National Radon Proficiency Program at


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