ANSI/AARST Radon Standards: What Each One Covers

ANSI/AARST radon standards are the written rulebooks that radon professionals in the United States follow when they test a building, install a mitigation system or build radon controls into a new home. Different documents cover different jobs: MAH-2023 for measuring radon in homes, SGM-SF-2023 for mitigating existing homes, and CCAH and RRNC for new construction. They are voluntary, but they are the benchmark a careful contractor works to, and the one you can hold a contractor to in writing.

TL;DR

• ANSI/AARST standards are voluntary, consensus-based documents for radon measurement, mitigation and radon-resistant construction, developed by the AARST Consortium on National Standards.
• MAH-2023 covers measuring radon in single-family homes. SGM-SF-2023 covers reducing soil gas entry in existing homes. CCAH and RRNC cover rough-ins in new homes.
• MS-QA and MS-PC set the quality and instrument requirements behind the measurement devices and labs.
• EPA says use of the standards is not required, but where a state has no mitigation rules, it recommends systems conform to the current voluntary consensus standards.
• Ask any contractor which standard and which edition they work to, and how they will verify the result after installation.

Table of Contents

• What ANSI/AARST standards are and who writes them
• Which standard covers what
• Measurement: what MAH-2023 is for
• Quality assurance behind the device
• Mitigation: what SGM-SF-2023 governs
• New construction: CCAH, RRNC and CC-1000
• Are the standards legally required?
• What to ask before you hire
• How we put this to work
• FAQ
• Sources

What ANSI/AARST standards are and who writes them

AARST is the American Association of Radon Scientists and Technologists. It is accredited by the American National Standards Institute (ANSI), and the standards are developed through the AARST Consortium on National Standards, which publishes them for measuring radon, mitigating it and building to prevent it. That is why you see the two names joined: ANSI accredits the process, and AARST runs it.

The word "consensus" matters. These documents are not written by one company or one regulator. They come out of a process with committees, public review and balloting. ANSI accreditation adds ongoing oversight and audits to make sure that process is followed and keeps improving. For you as a homeowner, the practical meaning is simple: the minimum requirements are public, written down and reviewed, not a contractor's private habits.

The standards also sit comfortably inside federal policy. Under the National Technology Transfer and Advancement Act and OMB Circular A-119, reliance on privately developed voluntary consensus standards is generally preferred over agencies inventing their own. EPA's own program guidance says the agency has moved from developing its own technical guidance toward participating in the voluntary consensus standards process to deal with technical issues. So when you read EPA material on radon testing or mitigation, you are often reading guidance that points back to these standards.

Which standard covers what

The names look like alphabet soup, but each one has a narrow job. This table matches the common ones to the situation you are probably in.

The descriptions above come from AARST's standards page, which also lists the current editions. Editions change, so always check the year in the name. A contractor quoting an older edition is not necessarily wrong, but you should know which one governs your job.

Measurement: what MAH-2023 is for

If you are testing a house, MAH-2023 is the one that matters. It sets out how to measure radon and radon decay products in single-family homes so the result is reliable enough to decide whether you need a mitigation system. The 2023 revision also clarifies professional qualifications, onsite documentation and reporting, which is the part buyers, sellers and agents care about most. A result you can't document is a result nobody will rely on at closing.

Closed-building conditions and test length

Testing conditions drive accuracy more than anything else. EPA's home buyer's and seller's guide recommends for short-term tests that you keep closed-building conditions for at least 12 hours before the test and throughout it, with a minimum test duration of 48 hours. In practice that means windows and exterior doors shut apart from normal entry and exit, and no whole-house fans or open fireplace dampers running.

Two things follow from that. First, a test that was run with a window cracked for a spring breeze is not a test you can trust. Second, 48 hours is a floor, not a target. If you want to understand why a longer window can give a steadier number, our article on radon test duration walks through it. Where you place the device matters as well, and we cover that in radon test placement.

Why documentation is part of the standard

In a home sale, the number is only half the product. The other half is the paper trail: who placed the device, where, when, under what conditions, and which device and lab produced the result. A tester working to the standard produces that record as a matter of routine. If you are a seller handing a report to a buyer's agent, or an agent reviewing one, that record is what prevents a retest. For how the numbers play out in a contract, see our piece on radon contingency clauses.

Quality assurance behind the device

You will rarely read MS-QA or MS-PC yourself, but they matter because they sit under every result. MS-QA sets minimum quality-system requirements for radon measurement systems. MS-PC sets the performance criteria and testing procedures for instruments and systems that quantify radon gas in air. Together they answer a question homeowners rarely think to ask: is the device on my basement shelf actually accurate?

A professional who works within this framework is using calibrated, properly handled equipment and keeping the records to prove it. That is a quiet but real difference between a professional test and a result nobody can defend.

Mitigation: what SGM-SF-2023 governs

When a test comes back elevated, SGM-SF-2023 is the standard that applies to fixing an existing single-family home. It specifies practices, minimum requirements and general guidance for reducing soil gas entry into existing homes, which covers radon as well as chemical vapors and other hazardous gases from the soil.

EPA's buyer's and seller's guide describes the typical outcome: most systems use vent pipes and fans to draw radon from beneath the home and release it above the roofline. The same guide notes that EPA does not recommend sealing alone to limit radon entry. Sealing cracks has a role as part of a system, but it is not a substitute for one.

System design follows the foundation

The standard is a framework, not a one-size-fits-all blueprint. A slab-on-grade house, a basement with a sump, a block wall foundation and a crawl space each call for different suction points, pipe routing and sealing. That is the reason we measure and design for the specific house rather than quoting from a template. If you want to see how the approaches differ, read about radon mitigation methods, and for crawl spaces specifically, crawl space radon mitigation.

Verification is how you know it worked

Installing a fan is not the finish line. The finish line is a follow-up measurement showing the home is below your target. A system with no verification test is a system you are trusting on faith. Ask for the post-installation result in writing, with the testing conditions recorded. If a system you already have seems to be underperforming, our list of checks to run when mitigation isn't working is a good first stop, and a fan that has failed is a repair job rather than a reason to start over.

New construction: CCAH, RRNC and CC-1000

Building radon controls into a new house costs far less than retrofitting one later, and the standards reflect that. CCAH and RRNC specify minimum rough-in requirements for radon control components in new homes under construction. ANSI/AARST CCAH-2020-0523, revised in May 2023, covers rough-in for new one- and two-family dwellings and townhouses. It also addresses verifying radon levels once the house is built and, if needed, activating the system.

That last point is the one buyers of new homes miss. A rough-in is passive plumbing: a pipe through the slab and up through the roof. It is not a working mitigation system until a fan is added, and you only know whether you need one after testing the finished house. Our articles on radon in new homes and new construction radon testing explain the sequence.

For commercial, multifamily and school buildings, CC-1000 is the relevant document. If you own apartments or an office, the practical question is usually how to get a compliant result without disrupting tenants. See radon in apartments and commercial radon mitigation.

Are the standards legally required?

Not by themselves. EPA's program guidance states that use of the standards is not required, and it encourages people to review state and tribal standards too. The same guidance calls citing or incorporating current radon consensus standards in state and tribal programs a best practice.

That leaves a gap worth understanding. A standard becomes binding when a state, a county, a building code or a contract adopts it. Where a state has no mitigation regulations, EPA's buyer's and seller's guide recommends that systems conform to its most current voluntary consensus-based standards. So even when no law demands it, the recommended benchmark is the same.

Three practical ways to make a standard enforceable on your job:

1. Put it in the contract. Name the standard and the edition in the written quote.
2. Ask for documentation that matches it: a design based on measurements of your foundation, and a post-installation test result.
3. Check your state and local rules. Ohio, Kentucky and Indiana homeowners in the Cincinnati area should confirm what their own state and municipality require for testers and mitigators before hiring.

To confirm the current edition of any standard, EPA recommends checking the ANSI Bookstore, the AARST standards site and EPA's own standards page for updates.

Our perspective

We treat the ANSI/AARST standards as the floor, not the finish line. A standard tells you the minimum a system must do. It can't tell you how to route a pipe through a particular 1950s block foundation or where the suction will actually reach under a slab that was poured in three sections.

That is why radon mitigation is the only thing we do. Every job starts with measurements of the specific house, and the design follows what we find. We quote in writing at a fixed price, with no added costs after the quote, and every mitigation includes post-installation verification testing so the result is a number you can see, not a promise. Our installations are ANSI/AARST certified, and we give you documentation suited to a real estate transaction.

Our advice to homeowners is simple. Don't ask a contractor whether they follow the standard, because everyone says yes. Ask which standard, which edition, what the design is based on, and what the verification test will show. A contractor who answers those plainly is a contractor worth hiring.

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What to ask before you hire

You do not need to read a standard cover to cover to use it. These questions put it to work.

For testing

• Which standard and edition do you test to?
• How will you maintain closed-building conditions, and for how long before and during the test?
• Where will the device go, and why there?
• What documentation will I receive, and will it hold up in a sale?

For mitigation

• What did you measure or inspect to design the system for my foundation?
• Is the quote fixed and in writing, and does it say what happens if the design has to change?
• Will you run a verification test after installation, and will I get the result in writing?
• Who do I call if the fan stops working?

For new construction

• Is the rough-in installed to CCAH or RRNC, as applicable?
• Who tests the finished house, and who activates the system if the number calls for it?

Answers to these tell you more than any certificate on a truck door.

How we put this to work

We test, design and install radon systems across the Greater Cincinnati area, a region where geology makes radon a real concern for homeowners. Our work covers residential mitigation, verification testing, testing during a home sale, rough-ins for new builds, commercial and multifamily properties, and repair or fan replacement for systems that have stopped doing their job.

If you need a test, start with our radon testing service. If a result is high and you want a design based on your own foundation, see our radon mitigation systems and mitigation cost guide.

Already have a system with a failed fan or a reading that never dropped? We handle radon system repair and fan replacement. You can see everything we offer on our services page.

FAQ

What does ANSI/AARST stand for?

ANSI is the American National Standards Institute, which accredits standards-developing organizations. AARST is the American Association of Radon Scientists and Technologists, which develops the radon standards through its consensus process. Together, ANSI/AARST on a document means it was developed under an accredited process.

Which ANSI/AARST standard applies to testing my home?

MAH-2023 is the standard for measuring radon and radon decay products in single-family residences. It sets the protocols and minimum requirements used to determine whether mitigation is needed. It also covers professional qualifications, onsite documentation and reporting.

Do I have to use a contractor who follows these standards?

Use of the standards is not required by EPA, and whether they are binding depends on your state, locality and contract. EPA does recommend that mitigation systems conform to the current consensus standards where a state has no rules of its own. The easiest way to be protected is to name the standard and edition in your written quote.

How long should a radon test run?

For short-term tests, EPA's guidance recommends closed-building conditions for at least 12 hours beforehand and throughout, with a minimum of 48 hours of testing. Longer tests can smooth out day-to-day swings. Your tester should tell you in advance how long the device will stay and what you need to do.

Does a rough-in mean my new home is protected from radon?

Not yet. A rough-in installs the pipe and components, and the standards call for verifying radon levels in the finished house and activating the system with a fan if needed. Test the home after you move in, or before closing, to know where you stand.

Sources

• AARST Radon Standards
• EPA State Indoor Radon Grants voluntary consensus standards program guidance (EPA 402/B-19/080)
• EPA Home Buyer's and Seller's Guide to Radon
• 2023 ANSI/AARST Soil Gas and Radon Standards Released

Recommended

• Radon Test Placement: Where to Put Your Test in the Home
• At 4 pCi/L, Homeowners Should Confirm Radon Test Results First