Montgomery County Home Sale Radon Testing Requirements
Montgomery County Code § 40-13C requires most single-family homes and townhomes to be tested for radon before sale, performed up to one year before settlement — plus what's exempt, and why not every home inspector is qualified to satisfy a standard GCAAR radon contingency.
Direct answer
Yes. Montgomery County Code § 40-13C, "Radon test — single-family home," requires that a single-family home located in the county be tested for radon before completing a sale, with the test performed up to one year prior to the settlement date. The requirement applies to sales settling on or after October 1, 2016. Both the buyer and the seller must receive a copy of the results.
Who is required to test
§ 40-13C puts the obligation on the seller, and it doesn't go away depending on what the buyer does: the seller must either perform the radon test, or permit the buyer to perform it. If the seller offers the buyer that option and the buyer declines, the seller must still have the test performed — the statutory requirement doesn't disappear because the buyer passed on it. In every version of that sequence, the party actually placing the monitor should be a certified radon professional, not a DIY kit — see below. The code itself is silent on who pays; that's typically settled in the purchase contract.
What's excluded
The law's definition of "single-family home" includes detached homes and townhomes, but excludes units that are part of a condominium regime or a cooperative housing corporation — those sales aren't covered by this particular mandate. It also exempts foreclosures, sheriff's sales, tax sales, fiduciary transfers of an estate, and conversions to non-residential use or demolition. And per Montgomery County's own Department of Environmental Protection, the law does not apply within the Town of Kensington, the Town of Poolesville, or the Town of Barnesville — those three incorporated towns are specifically exempted from the county requirement.
Can a buyer or seller just use a DIY test kit?
Effectively, no — not for a real estate transaction that has to hold up in a sale. § 40-13C doesn't name a specific device or require a certified tester for the bare county requirement, but that's not the same as a DIY kit working in practice. If the contract includes a GCAAR Radon Inspection Contingency — the case in most Montgomery County-area resale contracts — the contingency itself requires the test to come from an NRSB- or NRPP-listed firm; a hardware-store kit does not satisfy that clause. Even outside a contingency, a mail-in DIY kit has practical problems a real estate deal can't absorb: lab turnaround runs days to weeks against a contract deadline measured in days, and passive results are easier to dispute than a professional continuous monitor's tamper-resistant, time-stamped data. A DIY kit might be legal to buy, but it is not a workable way to satisfy a real estate radon requirement or contingency.
Can a home inspector perform this test?
Not automatically. Maryland does not have a state law requiring general home inspectors to hold radon certification, so a validly licensed Maryland home inspector may or may not also be certified to test for radon. Most Montgomery County-area resale contracts use Greater Capital Area Association of REALTORS® (GCAAR) forms, and GCAAR's optional Radon Inspection Contingency specifically requires testing to be "done by a testing firm listed with the National Radon Safety Board ('NRSB') or the National Radon Proficiency Program ('NRPP')" using an EPA-approved method. A radon reading from an inspector who isn't separately NRSB- or NRPP-listed doesn't satisfy that contingency, even if the inspector is a fully licensed general home inspector. See our real estate radon testing page for the full breakdown of the GCAAR contingency.
How RADON & CO helps
RADON & CO provides 48-hour professional radon testing for real estate transactions, including fast scheduling, authorized access coordination, and electronic reporting — performed under NRPP certification #115300-RMP, which satisfies the GCAAR contingency's testing-firm requirement.
Official sources
- Montgomery County Code § 40-13C, Radon test — single-family home
- Montgomery County DEP: Radon and Buying or Building a Home
- EPA: Health Risk of Radon
Disclaimer: This page is educational and reflects our reading of the county code, county guidance, and GCAAR's publicly described contingency terms as of this writing. It does not replace legal, lender, HUD program, or environmental consultant guidance.
Quick answers
Can a buyer or seller just use a DIY radon test kit for a Montgomery County home sale?
No. Whether the seller is arranging the required test or the buyer is exercising a GCAAR Radon Inspection Contingency, the test needs to come from a certified radon professional listed with NRSB or NRPP — a consumer DIY kit doesn't satisfy the contingency and creates practical problems (slow lab turnaround, easily disputed results) for the bare county requirement too.
Is radon testing legally required to sell a home in Montgomery County?
For most single-family homes and townhomes, yes — Montgomery County Code § 40-13C requires a radon test within one year of settlement, performed by the seller or by the buyer with the seller's permission. Condos, co-ops, and homes in the Town of Kensington, Poolesville, or Barnesville are exempt.
Can my home inspector do the radon test during a Montgomery County home sale?
Only if that specific inspector is separately listed with the National Radon Safety Board (NRSB) or National Radon Proficiency Program (NRPP). Maryland does not require general home inspectors to hold radon certification, and GCAAR's standard Radon Inspection Contingency requires testing by an NRSB- or NRPP-listed firm and technician — an inspection by a non-listed inspector does not satisfy that contingency.