Real Estate Radon Testing for Buyers, Sellers and Agents

Built for contract timelines

We focus on fast scheduling, clear communication, and clean electronic reports that help keep your transaction moving.

Agent-friendly access

Sentrilock access may be available when authorized. We can also coordinate with listing agents, homeowners, tenants, or property managers depending on the property.

Montgomery County's home-sale radon law: Section 40-13C

Montgomery County Code § 40-13C, "Radon test — single-family home" (Chapter 40, Article III), requires that a single-family home located in the county must be tested for radon before completing a sale, with the test performed up to one year prior to the settlement date. It applies to sales settling on or after October 1, 2016.

Who performs the test

The code 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 opportunity and the buyer chooses not to test, the seller must still have the test performed — the statutory requirement that a test happen belongs to the seller by default, and it doesn't disappear just because the buyer passed on doing it themselves. Both the buyer and the seller must receive a copy of the results. In every version of that sequence, the party actually placing the monitor should be a certified radon professional: it's what the region's standard contingency requires when one is in play (below), and it's the only version of "the test happened" that a buyer, a title company, or a lender will treat as settled rather than disputable. The county code itself doesn't say who pays for the test; that's negotiated in the purchase contract.

What's excluded

§ 40-13C's definition of "single-family home" covers detached homes and townhomes, but specifically excludes units that are part of a condominium regime or a cooperative housing corporation — a condo or co-op sale is not subject to this particular testing mandate. The law also exempts sales that are foreclosures, sheriff's sales, tax sales, fiduciary transfers of an estate, or conversions to non-residential use or demolition. And — a detail specific enough that most radon or real estate content misses it — homes in the Town of Kensington, the Town of Poolesville, and the Town of Barnesville are exempted from this county law entirely, per Montgomery County's own Department of Environmental Protection.

The GCAAR Radon Inspection Contingency

Separately from the county's own testing mandate, most Montgomery County, DC, and Northern Virginia resale contracts are written on Greater Capital Area Association of REALTORS® (GCAAR) forms, and GCAAR's standard purchase agreement includes an optional Radon Inspection Contingency that buyers commonly add. That clause gives the buyer a window — at the buyer's discretion and expense — to have the property tested for radon, and it's specific about who is allowed to do that testing: an NRSB- or NRPP-listed firm only. The full contingency language, as it appears in the standard form, reads:

RADON INSPECTION CONTINGENCY:

A. This Contract is contingent until 6 p.m. on the ____ Day after the Date of Ratification ("Deadline") to allow Buyer, at Buyer's discretion and expense, to have the Property inspected for the presence of radon. Inspection to be done by a testing firm listed with the National Radon Safety Board ("NRSB") or the National Radon Proficiency Program ("NRPP") using a U.S. Environmental Protection Agency ("EPA") approved testing method. Testing and retesting devices, if applicable, to be placed and retrieved by an NRSB or NRPP-listed technician or their authorized subcontractor. This contingency will terminate at the Deadline unless by the Deadline, Buyer Delivers to Seller a copy of the radon testing report which confirms the presence of radon that equals or exceeds the action level established by the EPA together with either 1 or 2:

1) Radon Testing Notice (GCAAR Form "Radon Testing Notice and/or Addendum/Release") requiring Seller at Seller's expense prior to Settlement to remediate the radon condition; or stipulating a dollar credit, as allowed by the Lender, to be paid at Settlement by Seller towards Buyer's charges to buy the Property. In the event that Seller agrees to remediate the radon condition, such work shall be performed by a NRSB or NRPP-listed remediation firm who will provide written verification that the required remediation has been performed, including test results demonstrating that the presence of radon is below the action level established by EPA.

If Seller elects not to perform in accordance with the Radon Testing Notice or makes another offer, Seller will Deliver Notice to Buyer of such decision within 3 Days after Delivery of the Radon Testing Notice.

Within 3 Days after Delivery of Notice from one party, the other party may:

• Deliver Notice accepting the terms contained in the other party's Notice; OR
• Deliver Notice continuing negotiations by making another offer; OR
• Deliver Notice that this Contract will become void at 6 p.m. on the 3rd Day following Delivery, unless the recipient Delivers to the other party Notice of the acceptance of the last Delivered offer prior to that date and time, in which case this Contract will remain in full force and effect. Seller may not exercise this option as the first response to Buyer.

Failure of either party to respond within 3 Days after Delivery of a Notice from the other party will result in acceptance by both parties of the terms of the most recent Notice.

2) Notice declaring this Contract void.

Reproduced as standard GCAAR contract language for reference. Always confirm the current, effective version of this form with your agent or GCAAR directly before relying on it in a transaction — forms are periodically revised.

Can a buyer or seller just use a DIY test kit?

No — for a real estate transaction, the radon test needs to come from a certified radon professional, not a DIY kit. That's true whether or not a GCAAR contingency is in the contract. When the contingency above is in play, it says so explicitly: testing "done by a testing firm listed with the National Radon Safety Board ('NRSB') or the National Radon Proficiency Program ('NRPP')" — a consumer kit from a hardware store does not satisfy that clause, full stop. And even on a sale that's only meeting the bare § 40-13C requirement with no contingency attached, a DIY kit creates problems a real estate deal can't absorb: mail-in lab turnaround typically runs days to weeks against a contract deadline measured in days, the passive results are far easier for the other side to dispute than a professional continuous monitor's tamper-resistant, time-stamped data, and most agents, lenders, and title companies expect a report from a certified tester, not a self-administered kit. Whether the seller is the one arranging the test or the buyer is exercising a contingency, the practical answer is the same: it needs to be a licensed radon professional, every time.

Why this means a general home inspector usually can't do it

Maryland does not have a blanket state law requiring radon measurement to be performed by a certified technician — a home inspector can be fully, validly licensed to perform a general home inspection in Maryland without holding any separate radon certification. NRPP and NRSB certification is a distinct credential on top of that general home-inspector license, earned through its own training and testing. That gap matters directly under the GCAAR contingency: if a home inspector who is not separately listed with NRSB or NRPP places a radon monitor during a routine inspection, that reading does not satisfy a GCAAR Radon Inspection Contingency as written, regardless of how experienced or well-licensed that inspector is as a general home inspector. Buyers, sellers, and agents relying on the contingency should confirm the specific individual (not just the company) is NRSB- or NRPP-listed before treating a result as contract-satisfying. RADON & CO's founder holds NRPP certification #115300-RMP, satisfying that requirement directly.

What happens if results are elevated?

RADON & CO specializes in independent radon testing. If levels are elevated, we explain the report and recommend speaking with a qualified mitigation professional for mitigation options.

Official sources

• Montgomery County Code § 40-13C, Radon test — single-family home
• Montgomery County DEP: Radon and Buying or Building a Home
• RADON & CO Knowledge Center: full breakdown of the home-sale radon law

This section is educational and reflects our reading of the county code, county guidance, and GCAAR's publicly described contingency terms as of this writing. It is not legal advice — confirm current contract language and obligations with your agent, title company, or counsel.

Frequently asked questions