Radon Mitigation System Diagram: Labeled Parts and Required Clearances

What are the key radon mitigation system statistics?

Each line stands alone: figure, year, qualifier, and named source. The clearest conflict in the verified sources is the vertical window clearance — see stat 1.

1. 1ANSI/AARST SGM-SF-2023 §6.4.6(b) requires a radon exhaust to be at least 4 feet from an operable opening below it — double the 2-foot vertical relationship in EPA's 2025 Consumer's Guide to Radon Reduction, ANSI/AARST CCAH-2020-0523 §601.3, and the 2021 IRC Appendix AF §AF103.5.3.
2. 2A radon exhaust must be at least 10 feet above the grade nearest the discharge under ANSI/AARST SGM-SF-2023 §6.4.5, ANSI/AARST CCAH-2020-0523 §601.2(2), and EPA's 2025 consumer guide. The 2021 IRC Appendix AF requires roof termination but does not state a 10-foot-above-grade minimum.
3. 3Clearance from a wall that rises above the roof is 4 feet under ANSI/AARST SGM-SF-2023 §6.4.10(d), 10 feet under ANSI/AARST CCAH-2020-0523 §601.2(3), and 5 feet under Pennsylvania's 25 Pa. Code §240.308(b)(5).
4. 4ANSI/AARST SGM-SF-2023 states exhaust placement as geometry: a 45-degree directional spread must not encounter an opening, building material, or occupied breathing space within 10 feet, and an 11-degree straight-line trajectory must remain clear for 20 feet (§6.4.3 and §6.4.4).
5. 5ANSI/AARST SGM-SF-2023 sets a minimum vent-pipe capacity equal to a 3-inch inside-diameter pipe, raises the minimum to 4 inches where pressure-field analysis indicates more than 80 cubic feet per minute, and permits 2-inch pipe only where analysis verifies 40 cfm or less (§6.3.1 through §6.3.3).
6. 6ANSI/AARST SGM-SF-2023 §6.1.1 requires a suction pit to contain a cleared void of at least 0.25 cubic feet — approximately 2 US gallons of excavated material — unless excavation is impracticable.
7. 7Iowa's rewritten radon mitigation rule took effect July 1, 2026 and requires credentialed mitigators to follow the applicable ANSI/AARST mitigation standards as amended through August 1, 2025, naming SGM-SF-2023 for existing homes and SGM-MFLB-2023 for multifamily, school, commercial, and mixed-use buildings — Iowa Administrative Code 641—44.3(3)"c."
8. 8The Iowa rule in force before July 1, 2026 instead required EPA's Radon Mitigation Standards (EPA 402-R-93-078, October 1993, revised April 1994) and ASTM E2121, and converted every “should” in those documents into a “shall.” That clause is absent from the current chapter.
9. 9Iowa Administrative Code 641—44.10(3), effective July 1, 2026, exempts passive-system installers from credentialing, while 641—44.1(1) requires a credentialed specialist for passive-to-active conversion and modification of an existing active system.
10. 10Iowa's 2026 rule defines a passive mitigation system as a vertical vent pipe routed through conditioned space from the suction pit to 12 inches above the roof, relying solely on convective airflow and using no in-line fan — 641—44.2.
11. 11A credentialed Iowa mitigator must install a system that reduces radon below 4 pCi/L in the area or level where it is installed — 641—44.3(4)"e" — and accepting compensation for a system that fails to do so is an enforcement ground under 641—44.7(21).
12. 12EPA's 2025 consumer guide lists typical radon reduction of 50 to 99 percent for active sub-slab suction and 30 to 70 percent for passive sub-slab suction. These are published technique ranges, not predictions for an individual house.
13. 13ANSI/AARST SGM-SF-2023 §6.5.2 prohibits the fan in conditioned or occupiable space and directly beneath such space, including a basement, crawl space, or enclosed garage beneath living space; EPA's 2025 guide states the same principle in consumer language.
14. 14Every fan-equipped system needs two monitoring functions under ANSI/AARST SGM-SF-2023: a continuously viewable operating-range indication and an active failure alert that is audible, vividly visible, or electronic (§8.2.1 through §8.2.3). The functions need not be two separate physical devices.
15. 15The manometer on a radon pipe does not measure radon concentration. Michigan EGLE's January 29, 2025 guidance explains that it indicates pressure or airflow condition; only a radon test measures the concentration in the building.
16. 16EPA's 2025 guide recommends starting a post-mitigation radon test no sooner than 24 hours after the system is operating and within 30 days of installation. Iowa's 2026 rule uses the same window when the building owner has not waived the state testing requirements before mitigation begins — 641—44.3(4)"d."
17. 17Iowa HHS identified 11 jurisdictions with radon-resistant new-construction requirements before the 2026 state legislation, including Linn County, Bremer, Johnson, and Polk counties, and the cities of Altoona, Bondurant, Carroll, Iowa City, North Liberty, Norwalk, and Pella.

What does a radon mitigation system diagram show, and how does the system work?

A radon mitigation system lowers the air pressure in the soil under a building so soil gas moves into a pipe instead of into the house. A collection point below the slab, below a crawl space membrane, or inside a drain-tile loop connects to a vent pipe; in an active system, an in-line fan pulls on that pipe continuously and discharges the gas outdoors above the roof. EPA describes active sub-slab suction — also called sub-slab depressurization — as the most common and usually the most reliable method for homes with a basement or slab-on-grade foundation.

The physics is a pressure difference. Indoor air pressure is normally slightly lower than the pressure in the soil around a foundation, so the building draws soil gas in through cracks, joints, and openings. A mitigation system reverses that relationship under the slab. It is not a filter and it does not neutralize anything; it intercepts and redirects.

The path, in order

1. Collection. Soil gas gathers in a permeable zone — crushed rock under a slab, the space under a sealed crawl space membrane, a perforated drain-tile loop, or the void network inside a hollow block wall.
2. Suction point. A pipe penetrates the slab or membrane into that zone. Under the slab, material is excavated to create a void so the pipe draws from a pocket rather than pressing against dirt.
3. Vent pipe. Rigid pipe carries the gas upward, sloped back toward the suction point so condensation drains down rather than pooling.
4. Fan. In an active system, an in-line fan sits on a vertical run, outside conditioned space.
5. Exhaust. The pipe discharges outdoors, above the roof, away from anything that could draw the gas back in.
6. Monitoring. A viewable operating-range monitor shows whether the fan-equipped system remains within its established range. An active notification function warns when the fan or another mechanical component fails.
7. Verification. A radon test — not the gauge — establishes whether indoor concentration actually dropped.

Reading the labels on any radon diagram

Diagrams vary, but the vocabulary is consistent. Suction point and suction pit are the opening and the excavated void beneath it. Soil-gas retarder is the sheeting over crawl space soil. Riser is the vertical run of pipe. Manometer is the U-shaped fluid gauge. Termination or discharge point is where the pipe ends outdoors. Sub-slab depressurization and soil suction describe the same family of methods.

What are the parts of a radon mitigation system, and what governs each one?

This reference tracks 22 components that can appear in a residential radon mitigation diagram. Nearly every one carries a published requirement — a minimum size, spacing, prohibited location, or required label. The table pairs each component with the governing provision without turning the data into an installation sequence.

★ Directly checked in a current issuer publication or the standards publisher's official technical bulletin reproducing the current clause. ● Directly checked in the official 2021 IRC model-code publication; local applicability depends on adoption and amendment.

Table 1. Radon mitigation system component reference

Source: ANSI/AARST current standards catalogue; AARST Consortium, February 2024 SGM technical bulletin reproducing the harmonized clauses required by reference to SGM-SF-2023; International Code Council, 2021 IRC Appendix AF. Requirements are paraphrased because standards text is copyrighted. Verified July 24, 2026.

What are the required clearances for a radon vent pipe?

Four current primary references address radon exhaust placement, and they do not all set the same numbers. SGM-SF-2023, CCAH-2020-0523, and EPA's 2025 guide require at least 10 feet above grade; the 2021 IRC Appendix AF requires roof termination but does not state that grade-height minimum.

The clearest conflict is the opening below the exhaust. EPA, CCAH, and the 2021 IRC use a 2-foot vertical relationship in their respective provisions, while SGM-SF-2023 requires 4 feet from operable openings below the discharge; Iowa's current Chapter 44 incorporates SGM-SF-2023 for applicable credentialed existing-home work.

Table 2. Radon exhaust and termination clearances, four authorities compared

Source: AARST Consortium's February 2024 SGM technical bulletin, SGM-SF-2023 §§6.4.1–6.4.13; ANSI/AARST CCAH-2020-0523 §§601.1–601.4 in the official publisher viewer; International Code Council, 2021 IRC Appendix AF §AF103.5.3; EPA, 2025 Consumer's Guide to Radon Reduction. Verified July 24, 2026.

What does the clearance comparison show — and what does it not show?

How was this radon mitigation system dataset compiled?

This dataset is an editorial synthesis of primary-source requirements, not a field measurement, performance study, or survey. Each published value is paired with its authority, section, applicability, verification tier, source URL, and July 24, 2026 verification date so the tables and downloads can be reproduced.

How does the diagram change by foundation type?

Foundation type determines the collection method, and the collection method is what actually differs between one radon diagram and the next. EPA groups the basement and slab-on-grade approaches into four soil-suction methods — sub-slab, drain-tile, sump-hole, and block-wall — and describes sub-membrane depressurization as the most effective approach for crawl space homes. Homes with more than one foundation type may need a combination.

Table 3. Collection method by foundation, with the constraint that governs the drawing

Source: EPA, 2025 Consumer's Guide to Radon Reduction, “Radon Reduction Techniques”; ANSI/AARST SGM-SF-2023 clauses as cited. Verified July 24, 2026.

Foundation-system diagram set

Schematics, not to scale; they do not determine suction-point count, fan sizing, pressure-field extension, or code compliance. Verified July 24, 2026.

What EPA publishes for typical reduction by technique

These are published ranges for the method, taken from EPA's table. They describe what the technique has typically achieved, not what any particular installation will achieve.

Table 4. Typical radon reduction by mitigation technique

Source: EPA, Consumer's Guide to Radon Reduction: How to Fix Your Home, 402/K-10/005 (2025 printing), “Radon Reduction of Various Mitigation Techniques.” Verified July 24, 2026.

What is the difference between an active and a passive radon system?

The passive system, as Iowa defines it

Iowa's Chapter 44 defines a passive mitigation system as one that reduces radon without an in-line fan, relying solely on convective airflow upward in the vent pipe for sub-slab depressurization, and consisting of a vertical vent pipe routed through conditioned space from the suction pit to 12 inches above the roof. That dimension is part of Iowa's current regulatory definition and should not be generalized to every jurisdiction.

The credentialing asymmetry in Iowa

Under Iowa's current rule, installing a passive radon mitigation system — whether standalone or as part of radon-resistant new construction — is exempt from credentialing (641—44.10(3)). But converting a passive system to active operation, or modifying an existing active system, must be performed by a credentialed radon mitigation specialist (641—44.1(1)). The rule defines “radon system modification” as any change altering an active system's design, configuration, or operation — adding or relocating piping, fans, or suction points — and expressly excludes routine replacement of parts with equivalent components that don't affect function or layout.

What changes in the drawing

A passive diagram shows the collection layer, the sealed retarder, the T-fitting or equivalent connection, and the vertical vent stack — but no operating fan and no active-system fan monitor. New-construction rough-ins instead reserve what later activation would need. ANSI/AARST CCAH-2020-0523 §701.1 requires an accessible fan-clearance space at least 21 inches in diameter and 36 inches high, and §§701.3–701.4 address access and electrical supply. Section 501.11 requires labeling on the pipe and within 12 inches of the electrical panel to state that the rough-in has not been activated with a fan and cannot be verified without testing.

EPA's guidance closes the loop: even homes built with radon-resistant features should be tested after occupancy, and a qualified mitigator can add a vent fan to an existing passive system if the result is 4 pCi/L or higher.

Is the manometer on the pipe a radon meter?

No. The U-shaped gauge on a radon vent pipe measures air pressure inside the pipe, which indicates whether air is moving — that is, whether the fan is pulling. It tells you nothing about the radon concentration in the house. Michigan's Department of Environment, Great Lakes, and Energy addressed this directly in January 2025, with indoor radon specialist Leslie Smith III stating that the mitigation system manometer does not measure radon concentrations and that the only way to know a building's radon concentration is to conduct a radon test.

This is a common misreading of a radon system, and it matters because a normal-looking gauge can be mistaken for evidence of a low radon concentration.

How to read the gauge

EGLE describes the two states plainly. When air is moving in the system, the fluid sits offset — one side higher than the other, forming a shape like the letter J. When there is little or no air moving, the fluid levels out on both sides into a U shape, which typically means no electricity, a failed fan, or a blockage in the pipe from ice, debris, or an animal. EGLE notes that a zero reading can reflect loss of power, fan failure, or a blockage, and directs readers to have the system evaluated when an electrical cause is not apparent.

Table 5. What each device establishes

Source: Michigan Department of Environment, Great Lakes, and Energy, “Even homes with radon mitigation systems should test for radon every two years,” January 29, 2025; ANSI/AARST SGM-SF-2023 §8.2.1–8.2.2. Verified July 24, 2026.

Which standard actually governs a radon mitigation system?

Four documents are in play, and they occupy different roles. ANSI/AARST publishes the consensus standards — SGM-SF-2023 for existing one- to four-unit homes, SGM-MFLB-2023 for multifamily, school, commercial and mixed-use buildings, and CCAH-2020-0523 for new one- and two-family construction. The International Residential Code supplies Appendix AF as a model code that jurisdictions may adopt. EPA publishes consumer-facing guidance rather than a design standard. And the state decides which of these, if any, is legally binding.

• EPA's current consumer guide still points readers at ASTM E2121 — it advises verifying with the contractor that the radon mitigation standards, ASTM E2121 in particular, are properly met, and to check with the state radon office for state requirements. Iowa's rule, as of July 1, 2026, names the ANSI/AARST standards instead.
• Iowa's rule uses “IEA” for the Indoor Environments Association, formerly known as AARST. Iowa's rule defines both names and treats them as the same body.
• SGM-SF-2023 does not apply retroactively, with two exceptions: portions of an older system that are altered, and portions of an older system that don't comply with the exhaust-discharge requirements of §6.4 or the safe fan-location requirements of §6.5.2 (§2.2). Those two provisions reach backward.

What are Iowa's radon mitigation requirements in 2026?

Iowa rewrote Chapter 44 in 2026. The current rule was adopted by ARC 0290D, published May 13, 2026, and became effective July 1, 2026; it now incorporates the applicable ANSI/AARST mitigation standards as amended through August 1, 2025.

The rule change and the separate new-construction statute are different legal events. Chapter 44 governs credentialed mitigation work, while Iowa Acts Chapter 1124 directs the State Building Code Commissioner to adopt a passive Appendix AF method for specified new construction after the code requirement is adopted.

Table 6. Iowa's radon mitigation rule, before and after July 1, 2026

Source: Iowa Administrative Code 641—Chapter 44, edition in force immediately before July 1, 2026, and the current chapter adopted by ARC 0290D, both read as published PDFs at legis.iowa.gov. Verified July 24, 2026.

What can a radon mitigation system diagram not prove about a real system?

A labeled diagram tells you what the parts are and where they go. It cannot tell you whether a particular installation works. A diagram cannot establish:

• Whether the negative pressure field actually extends across the area it needs to reach, which is measured, not drawn
• How many suction points a given house needs — EPA notes the number depends on how easily air moves in the material under the slab and on the strength of the source
• Whether a drain-tile loop communicates well enough to serve as a plenum
• Whether the fan is correctly sized for the airflow and vacuum the design requires
• Whether the exhaust actually meets the clearances in Table 2 on that building
• Whether the electrical work meets code
• Whether the radon concentration indoors has come down

Only a radon test answers that last one. EPA recommends a post-mitigation test within 30 days of installation and no sooner than 24 hours after the system is running, suggests a two- to seven-day measurement with windows and doors closed for 12 hours before and during the test, and recommends an independent follow-up measurement.

What are the limitations of this reference?

• These tables and figures are reference data drawn from published requirements. They are not a design manual, installation guide, permit determination, code interpretation, engineering drawing, or substitute for a credentialed professional's building-specific diagnostics.
• Standards are copyrighted. Every requirement is paraphrased and cited to a section path rather than reproduced; readers who need the exact normative language should obtain the standard from its publisher.
• ANSI/AARST maintains its standards continuously, and values here reflect the designations and sources checked on July 24, 2026. The IRC is revised on a three-year cycle and adopted by jurisdictions with amendments.
• Where a cell in Table 2 says “not addressed” or “not specified,” that means the cited source does not state a value for that row. Silence is not permission.
• Rows marked ★ were directly checked in a current issuer publication or the standards publisher's official technical bulletin. Rows marked ● were directly checked in the official 2021 IRC model code, but local applicability depends on adoption and amendment.
• Nothing on this page is a measurement. We did not test, inspect, or measure a system. The EPA percentages in Table 4 are published technique ranges, not predictions or guarantees for an individual home.
• The SVG diagrams are original editorial schematics. They are not to scale and do not specify fan selection, pipe routing for a particular building, wiring, flashing, firestopping, drainage design, suction-point count, pressure-field extension, or project-specific discharge compliance.

Which claims were excluded because they could not be verified?

The publication gate removes rather than hides unsupported claims.

• No claim that Iowa Acts Chapter 1124 was already incorporated into the July 8, 2026 published Chapter 301. That edition still deletes residential-code appendices AA through CH and contains no radon provision.
• No claim based on unpublished or secondary descriptions of agency guidance. The page relies on the enacted act and the published administrative code.
• No claim that a public-review draft is the final purchased SGM-SF-2023 edition. The current designation comes from AARST's catalogue; the clause values come from the publisher's official February 2024 technical bulletin.
• No claim that the 2021 IRC Appendix AF governs every Iowa project. The model-code values are identified as model-code values, and applicability remains jurisdiction-specific.
• No national count of installed systems that meet these specifications. No primary dataset was found, and no estimate was created.
• No Cedar Rapids retrofit-permit conclusion. A permit determination requires the current issuing authority and the facts of the project.

Where can the dataset and diagrams be downloaded?

The files below are the machine-readable distributions of the visible tables and the versioned original diagram library. The specifications dataset contains one row per source-specific component, clearance, EPA performance, Iowa rule-comparison, or legal-status record.

How should this page be cited?

This block is a neutral bibliographic reference for editors, researchers, and data users. It does not request a citation or a link.

What are the most common radon mitigation system questions?

These answers restate the most searched component, clearance, monitoring, testing, and Iowa-status questions in standalone form.

What does a radon mitigation system look like?

An active system typically has a soil-gas collection interface, rigid vent piping, an in-line fan in a permitted non-occupied location, viewable operating-range monitoring, an active failure alert, outdoor discharge, and a separate radon test. A passive system has collection and vent piping but no operating fan or active-system pressure monitor.

How high does a radon vent pipe have to be?

At least 10 feet above the grade nearest the discharge under ANSI/AARST SGM-SF-2023 §6.4.5, ANSI/AARST CCAH-2020-0523 §601.2, and EPA's consumer guide. Above the roof itself, SGM-SF-2023 requires at least 1 foot above a pitched roof at the point penetrated, at least 18 inches above a flat roof, and at least 6 inches above the roof edge where the piping runs up the side of the building.

How far does a radon vent have to be from a window?

The answer depends on the authority. SGM-SF-2023 requires at least 10 feet horizontally to the side and at least 4 feet from an operable opening below the discharge; EPA's 2025 guide, CCAH-2020-0523, and the 2021 IRC Appendix AF use a 10-foot relationship that is relieved when the exhaust is at least 2 feet above the opening under their respective provisions.

What size pipe is used for radon mitigation?

At least the cross-sectional equivalent of 3-inch inside diameter under SGM-SF-2023 §6.3.1. It rises to 4-inch where pressure-field analysis shows the system needs more than 80 cfm, and 2-inch is permitted only where analysis verifies 40 cfm or less. The 2021 IRC Appendix AF §AF103.5.3 specifies gas-tight ABS, PVC, or equivalent pipe at least 3 inches in diameter for new construction.

Can the radon fan go in the basement?

No. SGM-SF-2023 §6.5.2 prohibits installing the fan in conditioned or occupiable space and directly beneath it, which rules out a basement, crawl space, or enclosed garage under living space. Permitted locations are attics, building exteriors, and garages that are not beneath occupiable space. The reason is containment: if a joint fails on the pressure side of the fan, that failure should not vent into the house.

Is the U-tube gauge on the pipe a radon meter?

No. It measures air pressure inside the pipe, which indicates whether air is moving. Michigan EGLE states that the manometer does not measure radon concentrations and that the only way to know a building's radon level is to conduct a radon test.

What does it mean when both sides of the manometer are level?

Michigan EGLE describes a level U shape as indicating little or no airflow, with possible causes including power loss, fan failure, or pipe blockage. A separate radon test is still needed to determine the indoor concentration.

What is the difference between an active and a passive radon system?

An active system uses an in-line fan; a passive system relies on convective airflow in a pipe routed through conditioned space. EPA lists typical reduction of 50 to 99 percent for active sub-slab suction and 30 to 70 percent for passive, and describes passive systems as generally less effective at high radon levels.

Can a passive system be converted to an active one?

Yes — EPA notes a qualified mitigator can add a vent fan to an existing passive system. In Iowa, that conversion must be performed by a credentialed radon mitigation specialist under 641—44.1(1), even though installing the passive system in the first place is exempt from credentialing under 641—44.10(3).

How many suction points does a system need?

It depends on the building. EPA states that the number and location depend on how easily air moves through the material under the slab and on the strength of the source, and that often only a single suction point is needed. It is determined by diagnostics, not by a rule of thumb.

When must the post-mitigation radon test happen?

EPA's 2025 guide recommends no sooner than 24 hours after the system is operating and within 30 days of installation. Iowa's 2026 rule uses the same window when the owner has not waived the state pre- and post-mitigation testing requirements before work begins; EPA recommends a two- to seven-day measurement and an independent follow-up test.

Does Iowa require a radon system in a new house?

Iowa Acts Chapter 1124 directs the State Building Code Commissioner to adopt a passive method from 2021 IRC Appendix AF for new one- and two-family construction commenced after adoption. The published July 8, 2026 edition of Iowa Administrative Code 481—Chapter 301 still deletes appendices AA through CH and contains no radon provision, so project-specific status must be confirmed in the current code and with the authority having jurisdiction.

Which primary sources support this page?

Every consequential value on this page traces to an issuing agency, standards publisher, model-code publisher, enacted statute, or official state publication.

1. AARST Consortium on National Standards. Current standards catalogue, including SGM-SF-2023, SGM-MFLB-2023, and CCAH-2020-0523
2. ANSI/AARST. SGM-SF-2023 — Soil Gas Mitigation Standards for Existing Homes, official online viewer
3. AARST Consortium on National Standards. SGM 2023 Technical Bulletin and Migration from RMS-MF, February 2024
4. ANSI/AARST. CCAH-2020-0523 — Reducing Radon in New Construction of 1 & 2 Family Dwellings and Townhouses — Rev. 5/23, official online viewer
5. ANSI/AARST. CCAH-2020-0523, Section 501, labels and rough-in requirements
6. ANSI/AARST. CCAH-2020-0523, Section 601, exhaust discharge requirements
7. ANSI/AARST. CCAH-2020-0523, Section 701, fan-clearance, access, location, and electrical provisions
8. International Code Council. 2021 International Residential Code, Appendix AF — Radon Control Methods
9. U.S. Environmental Protection Agency. Consumer's Guide to Radon Reduction: How to Fix Your Home, EPA 402/K-10/005, 2025
10. Iowa Administrative Code. 641—Chapter 44, Radon Mitigation Requirements, published May 13, 2026, effective July 1, 2026
11. Iowa Administrative Code. 641—Chapter 44, Minimum Requirements for Radon Mitigation, edition in force immediately before July 1, 2026
12. Iowa Administrative Rules. ARC 0290D notice detail
13. Iowa General Assembly. Iowa Acts Chapter 1124, House File 2297, approved May 19, 2026
14. Iowa Administrative Code. 481—Chapter 301, State Building Code, published July 8, 2026
15. Iowa Department of Health and Human Services. Radon Resources
16. Michigan Department of Environment, Great Lakes, and Energy. Even homes with radon mitigation systems should test for radon every two years, January 29, 2025
17. Pennsylvania. 25 Pa. Code §240.308, Radon mitigation standards for detached and attached residential buildings three stories or less in height

What changed in this version?