- The Official Six-Domain Blueprint
- How the Weights Compare
- Domain 1: Communicate with the Client (14%)
- Domain 2: Identify Radon Entry Points (17%)
- Domain 3: Maintain Jobsite Safety (15%)
- Domain 4: Implement Mitigation Installation Strategy (30%)
- Domain 5: Perform Post-Installation Tasks (17%)
- Domain 6: Operate in an Ethical and Professional Manner (7%)
- How the Blueprint Shows Up on Exam Day
- Sequencing Your Prep Around the Weights
- Frequently Asked Questions
- The Radon Mitigation Installer exam has six official domains whose weights add up to exactly 100%.
- Implement Mitigation Installation Strategy carries 30%, nearly double any other single domain.
- Ethics is only 7%, but Domains 1 and 3 together add another 29% of content.
- You face 95 delivered questions: 85 scored plus 10 unscored trial items, within two hours.
The Official Six-Domain Blueprint
If you are preparing for the Radon Mitigation Installer (RMI) credential from the National Radon Proficiency Program (NRPP), the single most useful document you can read is the exam blueprint. It tells you what the test measures and how heavily each area counts. The six headings and percentages below come from Appendix A of the NRPP Candidate Handbook (document 3-007-4 V7, revised May 4, 2023), and the weights total 100%.
This is the published blueprint for the supervised installer credential. It is not the outline for the radon measurement exams or for the mitigation supervisor credential, and it should not be mixed with them. If you are still sorting out what the credential is and how it differs from related ones, start with What Is RMI Certification? and then return here for the domain-level detail.
One honest caveat: this guide describes the verified published blueprint. It does not claim a separate 2026 revision of the RMI outline, because none is documented. When you read "2026" in this guide's title, treat it as "current as of our latest verification," not as a new blueprint.
How the Weights Compare
| Domain | Weight | Character of the content |
|---|---|---|
| 1. Communicate with the Client | 14% | Scope, expectations, documentation, homeowner interaction |
| 2. Identify Radon Entry Points | 17% | Diagnosing how and where radon enters a building |
| 3. Maintain Jobsite Safety | 15% | Hazard awareness, combustion safety, worker protection |
| 4. Implement Mitigation Installation Strategy | 30% | System design choices, materials, installation methods |
| 5. Perform Post-Installation Tasks | 17% | Verification, labeling, documentation, handoff |
| 6. Operate in an Ethical and Professional Manner | 7% | Professional responsibility, standards, integrity |
Two patterns stand out. First, Domain 4 alone is worth almost a third of the exam, so weakness there is very hard to offset elsewhere. Second, the remaining 70% is spread across five domains that are surprisingly close in size (14%, 17%, 15%, 17%, 7%), which means no one of them can be safely skipped. A candidate who only studies the hands-on installation material and ignores communication, safety and post-installation work is giving up a large share of the available points.
Domain 1: Communicate with the Client (14%)
It may seem odd that a technical trade credential tests communication, but installers work inside people's homes and are often the only company representative the homeowner sees. This domain checks that you can explain what you will do, what it will and will not accomplish, and what the client needs to know afterward.
What candidates must understand
Expect scenario-style questions about how an installer should interact with a client before, during and after a job.
- Explaining the proposed mitigation approach in plain language without overpromising results
- Setting expectations about disruption, access needs and system placement (for example, where a pipe or fan will be visible)
- Describing what the installed system requires from the occupant, such as noting and reporting a change in the system's operating indicator
- Handling documentation the client should receive and retain
- Recognizing when a question falls outside the installer's role and needs to go to the supervisor
Because RMI certification requires working under an NRPP-certified radon mitigation supervisor, some of the "who answers what" logic is baked into this domain. Know the boundary of your own role. If you want to see how that supervision requirement affects eligibility, read RMI Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Domain 2: Identify Radon Entry Points (17%)
You cannot design a good system for a house you have not diagnosed. Domain 2 covers the building-science reasoning behind radon entry: how soil gas moves, what drives it into a structure, and how to spot likely pathways on site.
High-value topics
This is where foundation type and construction details become exam material.
- The role of pressure differences and stack effect in drawing soil gas into a building
- Common entry routes: slab cracks, control and expansion joints, the cove joint where wall meets floor, utility penetrations, sumps, and openings in block walls
- How foundation types differ, including slab-on-grade, basement, and crawlspace, and why each calls for different diagnostics
- Recognizing conditions that complicate mitigation, such as poor sub-slab communication or competing exhaust appliances
- Using a visual inspection and simple diagnostic checks to inform the design
A useful way to study this domain is to mentally walk a house from the footing up and ask at every surface, "Could soil gas get through here, and what would I do about it?" Questions often present a building description and ask which condition is most likely contributing to radon entry, or which diagnostic step should come next.
Domain 3: Maintain Jobsite Safety (15%)
Radon installers cut concrete, work in crawlspaces and attics, handle electrical connections and operate around combustion appliances. Domain 3 tests whether you can do all that without hurting yourself, the occupants or the property.
What the domain targets
Safety questions tend to be practical and consequence-driven.
- Personal protective equipment appropriate to concrete cutting, dust, and confined or low-clearance spaces
- Dust control practices during coring and drilling
- Combustion appliance awareness, including backdrafting risk when a mitigation fan changes house pressures
- Electrical safety when wiring fans and disconnects
- Ladder, fall and general worksite hazard awareness
- Recognizing situations that require stopping work and consulting the supervisor
Backdrafting deserves special attention. A mitigation system changes how air and gases move in a building, and a candidate who understands why combustion appliances matter in that context will handle a whole family of scenario questions correctly. This domain sits close to Domain 4 in practice, since installation choices have safety consequences, so treat them as connected rather than separate silos.
Domain 4: Implement Mitigation Installation Strategy (30%)
This is the heart of the exam and the largest domain by a wide margin. At 30%, it is where passing and failing are most often decided. It covers choosing and executing an installation approach that follows the applicable mitigation standard.
Core content to master
Think in terms of the full system, from suction point to discharge point.
- Active sub-slab depressurization as the foundation for many installations, and the principles that make it work
- Suction point selection, pit size and placement, and how sub-slab material affects fan performance
- Pipe sizing, routing, slope and support, including condensation drainage considerations
- Fan selection and placement, with attention to location restrictions and the system's operating indicator
- Discharge point requirements, including height and distance from openings and other features
- Sealing: why cracks, joints and penetrations are sealed and which materials suit which conditions
- Alternatives and additions for other foundations, such as sub-membrane depressurization in crawlspaces and approaches for block walls
- Electrical connections, labeling and system identification
The exam supplies reference material in the testing platform, including SGM-SF-2023 and MAH-2023, along with a calculator and formulas. That is helpful, but do not mistake it for permission to skip preparation. Reference documents save you from memorizing exact figures, yet you still have to know where to look and how to apply what you find under time pressure. Practice navigating those documents quickly before test day.
When you drill this domain, work from installation scenarios rather than flashcards of definitions. A question might describe a basement with a particular sub-slab condition and ask which design adjustment is appropriate. Our RMI practice tests are organized so you can concentrate repetitions on exactly this kind of applied question.
Domain 5: Perform Post-Installation Tasks (17%)
The job is not finished when the last fitting is glued. Domain 5 covers the verification, documentation and handoff that turn an installation into a defensible, usable result.
What to know
Think of this as proving the system works and leaving a clear record behind.
- Verifying system operation after installation, including confirming the operating indicator reads as expected
- Confirming that sealing and connections are complete and that nothing was missed
- Labeling the system and recording the information that should be posted and retained
- Providing the client with documentation and operating guidance
- Understanding the relationship between installation and post-mitigation radon testing, and the installer's role in coordinating or recommending it
- Cleanup and restoring the work area
Be careful about role boundaries here. Testing and installation are different disciplines, and candidates sometimes lose points by assuming the installer performs or interprets work that belongs to a measurement professional. Read each question for who is responsible for what.
Domain 6: Operate in an Ethical and Professional Manner (7%)
Ethics is the smallest domain, and that tempts candidates to skim it. Resist that. Seven percent of 85 scored items is still a meaningful handful of questions, and they are typically among the most winnable because they reward sound judgment and familiarity with the credential's own rules.
Where the questions come from
Think about the commitments you make when you certify.
- The Statement of Professional Responsibility every candidate signs as part of the process
- Honest representation of qualifications, services and results
- Working within the limits of your certification and under proper supervision
- Following the applicable standards and regulations rather than cutting corners to save time or money
- Respecting client confidentiality and property
Ethics also connects to renewal, since maintaining certification involves ethics compliance. If you want the longer-term picture of what staying certified looks like, the details are covered in our cost breakdown at RMI Certification Cost 2026: Complete Pricing Breakdown.
How the Blueprint Shows Up on Exam Day
Knowing the domains is only half the picture. You also need to understand the container they arrive in. The exam is currently delivered through Certiverse with live remote proctoring. You receive 95 questions in total: 85 are scored and 10 are unscored trial items, a structure in place since October 1, 2024. You cannot tell which ones are the trial items, so treat every question as if it counts. The testing limit is two hours.
Remote proctoring brings its own logistics. You need photo ID, a live proctor will be present, and you will be asked to complete a room scan. One bathroom break of up to five minutes is permitted. Inside the platform you have the reference documents and calculator noted above, but personal reference books are not allowed.
| Exam detail | Current specifics |
|---|---|
| Delivery | Certiverse, live remote proctoring |
| Questions | 95 delivered: 85 scored, 10 unscored trial items |
| Time limit | Two hours |
| Exam fee | $125 |
| Retake rule | 30-day wait; at most four attempts in 12 months |
| Validity of results | Examination results usable for one year |
Note that the older Candidate Handbook mentions a different delivery vendor and an 85-total-item statement. The current Certiverse logistics above supersede those older handbook details, which is why it is worth checking the NRPP exam page before you schedule. The blueprint percentages, however, come from the handbook appendix and remain the verified published weights.
For the money side, the exam fee is separate from training, and initial certification and biennial renewal each carry their own fee. The full arithmetic is laid out in the pricing breakdown. If you are wondering how the exam compares to others in difficulty, see How Hard Is the RMI Exam? Complete Difficulty Guide 2026, and for how scoring works, see RMI Passing Score 2026: Exactly What You Need to Pass. Passing follows the issuer's competency standard, and no unsupported numerical cut score should be assumed.
Key Takeaway
Because retakes require a 30-day wait and are capped at four attempts in 12 months, a failed first attempt costs you time as well as the $125 fee. Preparing against the weighted blueprint the first time is the cheapest route.
Sequencing Your Prep Around the Weights
Training requirements already give you a head start: candidates complete approved measurement training of at least 12 hours and mitigation training of at least 20 hours, and those certificates are usable for two years. Use your course materials as the content source and the blueprint as the allocation guide. A sensible order is to begin with the heaviest domain, because it needs the most repetition, and to pair related domains so the connections reinforce each other.
Domain 2 and Domain 3 together
- Learn entry pathways and pressure principles first; they underpin every design decision
- Pair them with jobsite safety, especially combustion appliance and backdrafting concepts
Domain 4 deep dive
- Work through suction points, piping, fans, discharge and sealing in system order
- Practice locating answers quickly in SGM-SF-2023 and MAH-2023
Domains 5, 1 and 6
- Cover verification, labeling and documentation, then client communication
- Finish with ethics and professional responsibility, then take a full timed practice exam
Adjust the pace to your own schedule and prior experience; the point is the proportion, not the calendar. For a broader plan and technique advice, see the RMI Study Guide 2026: How to Pass on Your First Attempt, and for a compact last-day review, the RMI Cheat Sheet 2026: One-Page Review of Must-Know Facts.
Frequently Asked Questions
They are Communicate with the Client (14%), Identify Radon Entry Points (17%), Maintain Jobsite Safety (15%), Implement Mitigation Installation Strategy (30%), Perform Post-Installation Tasks (17%), and Operate in an Ethical and Professional Manner (7%). The weights total 100% and come from the NRPP Candidate Handbook's Appendix A.
Implement Mitigation Installation Strategy, at 30%, is the largest. It covers system design and installation methods, so it should receive the biggest share of your study time, though the other five domains still collectively make up 70% of the exam.
No. The platform provides SGM-SF-2023, MAH-2023, a calculator and formulas, but personal reference books are not permitted. Practice using the provided documents so you can find information efficiently within the two-hour limit.
You will see 95 questions, of which 85 are scored and 10 are unscored trial items. You cannot tell them apart, so answer every question carefully. For more on scoring, see our RMI pass rate discussion, which stays qualitative rather than citing unverified figures.
Yes. This blueprint applies specifically to the supervised Radon Mitigation Installer credential. The measurement and mitigation supervisor credentials have their own outlines, so do not substitute their material when studying. Related background is in What Is RMI?, and state licensing rules, where they exist, are separate from this exam.
Mastering the six domains means matching your effort to the published weights, leaning hardest on installation strategy while still respecting the smaller areas. When you are ready to test yourself against realistic scenarios, head back to the main RMI practice site and start working through questions domain by domain.