Montgomery County Radon Test for Home Sales
Montgomery County requires a radon test before most single-family homes and townhomes settle. We run it with an NRPP-listed continuous monitor and send both sides a written report with the hourly readings.
Test within a year of settlement.
Since October 1, 2016, Montgomery County Code Section 40-13C (Bill 31-15) has required a radon test before a covered home is sold.
- Timing. The test must be done less than one year before the settlement date.
- Who tests. The seller either runs the test or lets the buyer run it. Either side can hire a professional.
- Both get the results. The buyer and the seller each receive a copy.
- Approved device. The test must use a County-approved device. Devices on the National Radon Proficiency Program list qualify, and our SunRADON 1028 XP is on it.
- No required fix. The law sets no pass or fail level and does not require mitigation. A high result becomes part of the negotiation.
Which homes and sales are covered.
Covered
Single-family homes, detached or attached. That means most houses and townhomes in the County.
Not covered
Units in a condominium or a housing cooperative.
Exempt sales
Sales exempt from Maryland transfer tax; foreclosure and lender-owned sales; sheriff's, tax, partition and court-trustee sales; transfers by an estate, trust or guardian; and homes the buyer will demolish or convert to non-residential use.
Book it early, not at the deadline.
Sellers
Test before you list. The result is good for a year, and a high number leaves time to mitigate and retest instead of negotiating under a deadline.
Buyers
If the seller lets you run the test, call as soon as the contract is signed. The test needs 12 hours of closed-house conditions and 48 hours of readings, so we schedule it to report inside your contingency.
If the result is high
We refer you to licensed mitigation contractors and run the post-mitigation retest. We do not install systems, so the number is the number.
Common questions.
Can I use a test kit from the hardware store?
The County allows any approved device, including some short-term kits. A professional continuous monitor logs every hour, shows whether the house was kept closed, and gives buyer and seller a report from an independent party, which tends to settle questions faster.
Does a high result stop the sale?
No. The County law does not set a pass level or require mitigation. Buyers and sellers usually agree on mitigation or a credit in the contract. The EPA recommends fixing a home at 4.0 pCi/L or above.
Who pays for the test?
The County law does not say. It is usually settled in the sales contract, so ask your agent.
Is my town included?
The rule covers most of the County. A few municipalities, such as Barnesville, Kensington and Poolesville, are not covered, and Rockville may also be excluded. Ask your agent if your home is inside a town or city limit.
Can you test for mold on the same visit?
Yes. The lowest level is where radon is measured and where moisture problems usually start.
Where does this come from?
Montgomery County Code Chapter 40, Section 40-13C, added by Bill 31-15, effective October 1, 2016. This page is a plain-language summary, not legal advice.
Selling soon? Get the test on the calendar.
Weekdays 8 to 5. Tell us your settlement date and we will schedule around it.