Home Inspector Radon Testing: Rules, Devices, Pricing

Short answer: Radon is outside the standard home inspection, so it is an add-on. EPA's guidance for real estate tests is a minimum of 48 hours, using either two passive devices or a continuous monitor, under closed-house conditions, with steps to prevent or detect interference, and a fix recommended at 4 pCi/L or higher. EPA does not credential testers. Your state might: some license radon testers themselves, some accept NRPP or NRSB certification, and many set no rule. Check your state radon office before your first paid test.

Radon is one of the most common add-ons inspectors sell, and one of the few where the method is spelled out in federal guidance. That makes it easier to do well than most services. It also means a test done carelessly is easy to challenge.

This guide covers EPA's real estate protocol, the devices, interference, the state credentialing picture as of September 2026, NRPP and NRSB certification, how to price it, and how to deliver the result as its own report.

Radon is an add-on, not part of the standard inspection

Standards of practice generally exclude radon. The InterNACHI Standards of Practice, for example, say the inspector is not required to determine "the presence of airborne hazards, including radon."

So a radon test is a separate service, with its own scope in your inspection agreement and its own fee. It also carries its own credential question, which most other add-ons do not.

EPA estimates radon causes about 21,000 lung cancer deaths a year in the United States, citing its 2003 risk assessment. Clients and agents know radon matters. What they need from you is a result they can rely on in a negotiation.

EPA's real estate protocol

EPA's guidance for testing during a sale is in the Home Buyer's and Seller's Guide to Radon (EPA 402/K-24/001, revised March 2024). The key points:

Your state may publish its own protocol that goes further. Where it does, the state's version is the one you follow. EPA's guide itself tells people testing to follow the protocol for their area.

Where the protocol trips inspectors up

Placement and timing cause most problems. A device on the kitchen counter, a test started the moment you arrive without 12 hours of closed-house conditions, or a two-day test during a storm all give the other side of the negotiation a reason to reject the result. Write down where you placed the device, when you started and stopped, and what conditions you observed. That record is the test.

Device types

EPA groups radon test devices into passive and active.

For a real estate practice, the practical choice is usually between lab-analyzed passive devices, which cost little per test but add shipping and lab time, and a continuous monitor, which costs more to buy and maintain but gives a result when you pick it up. Whichever you use, follow the manufacturer's calibration requirements and any state requirement for device approval or calibration, and keep the records.

Interference: prevent it and detect it

EPA says tests in real estate transactions should prevent or detect interference. Its guidance lists ways to do both:

• A device that records radon or decay product levels frequently, so unusual swings show up
• A motion detector, to show whether the device was moved or conditions changed
• A proximity detector, to show people in the room during the test
• Recording barometric pressure and temperature, to spot weather effects and opened doors or windows
• Tamper-proof seals on windows
• A signed non-interference agreement from the seller or occupant

EPA also notes that interfering with a test device or with closed-house conditions may invalidate the result "and is illegal in some states." Give occupants written instructions at placement. Record what you find at retrieval: windows open, device moved, fans running. If the data or the site suggests interference, say so in the report and recommend a retest rather than reporting a number you do not trust.

Who can test: EPA, states, NRPP and NRSB

EPA does not credential radon testers. States that receive EPA radon grants must list credentialed providers, meaning a state license or NRPP or NRSB certification, and EPA points residents to their state radon office.

That leaves the credential question to your state. The American Lung Association's 2023 summary of state programs is the most complete public list we found:

ALA reports that twenty states with 48% of the nation's population have adopted some form of radon industry regulation, and that Florida alone runs its own exam. Two caveats matter. The list is from August 2023 and states change their rules. And it does not separate testing from mitigation, so a state on the list might regulate only one of them. Confirm with your state radon office before you sell a test. NRPP gives applicants the same advice.

If your state is not on the list, you may not need any credential to test. Many inspectors certify anyway, because agents and relocation companies ask, and because the course teaches the protocol.

NRPP and NRSB measurement certifications

The two national programs each offer an individual-level and an entry-level measurement credential. Figures from their own pages, as of September 2026:

NRSB's pass mark is 70% with a virtual proctor and a wait of 14 days before a retest. NRPP requires a 30-day wait between attempts, allows at most four attempts in 12 months, and keeps a passing score valid for one year.

NRPP's field technician credential needs a supervising certified RMP, so a solo inspector certifying through NRPP needs the RMP level. Since September 1, 2025, an RMFT has seven business days to report a change of supervisor before the certification is inactivated. NRSB works the same way: its RMT places and retrieves devices under the supervision of a certified RMS or an accredited laboratory. A multi-inspector firm can certify the owner at the higher level and field staff at the technician level under that supervision. Check that your state accepts the credential you choose. For how radon fits alongside other credentials, see home inspector certification and indoor air quality certification.

Pricing a radon test

There is no national price list, and forum figures are not a sound basis. Price from your own costs, as with any ancillary service.

Then work out how many tests a year you need to break even. In some markets radon is requested on most transactions and a monitor pays for itself quickly. In others it sits in a cupboard. How to price ancillary services has the full method, and how much a home inspector should charge covers the base fee it sits on.

Two pricing traps are specific to radon. First, do not discount it into a bundle below its own break-even, since it is the add-on with the extra trip. Second, if a retest is needed because of interference, decide in advance, in your agreement, who pays for it.

Tell your E&O carrier before you start. See home inspector insurance.

Delivering radon results as their own report

A radon result arrives days after the home inspection report, and it is often read by different people for a different purpose. It works better as its own document.

In Binsr, one inspection can produce multiple reports, such as the main inspection plus a radon report, each with its own template. Each report can be locked or hidden from the client. That lets you deliver the home inspection report the same day, keep the radon report hidden while the test runs, and release it when the result is in, all under the same inspection record.

Build the radon template around the protocol: device type and serial number, placement location and height, start and stop times, closed-house and weather observations, interference measures used, the result and EPA's action level. When every test fills the same fields, the record is complete even on a rushed day.

You can also sell radon at booking. Binsr's booking pricing rules work on any custom booking question, so a "Add a radon test?" question can add the fee and extend the scheduled time automatically.

Frequently asked questions

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