- Which Blueprint Are You Studying For?
- The Six Domains and Their Weights at a Glance
- Domains 1 and 2: General and Inspection
- Domain 3: Diagnostics (28%)
- Domain 4: System Design (24%)
- Domain 5: ASD Mitigation System Installation (23%)
- Domain 6: Post-mitigation (8%)
- The Legacy Section Weights You May Still See
- Exam Mechanics, Fees and Prerequisites
- Sequencing Your Prep by Domain
- Frequently Asked Questions
- The announced NRPP six-domain blueprint weights Diagnostics 28%, System Design 24%, and ASD Mitigation System Installation 23%, totaling 75% of the exam.
- The six published weights sum to 100%: General 4%, Inspection 13%, Diagnostics 28%, System Design 24%, Installation 23%, Post-mitigation 8%.
- Question counts conflict: the live page states 165 total (150 scored) while the May 2026 update specifies 175 total (160 scored); both allow three hours.
- The announced blueprint was not confirmed as the form every candidate currently receives, so verify your version with NRPP before booking.
Which Blueprint Are You Studying For?
The Radon Mitigation Specialist (RMS) credential is issued by the National Radon Proficiency Program (NRPP). Before you build a study plan around any domain list, you need to understand a wrinkle that most prep sites gloss over: there are two descriptions of the RMS exam in circulation, and they do not match.
The first is the operational form described on NRPP's live exam page, effective October 1, 2024. The second is the announced revision, labeled "2025 RMS" in NRPP's Credentialing Updates presentation of May 2026 and reported in The Radon Reporter (2026 Issue 1). That revision approved in February 2026 carries the six-domain blueprint this article covers. The published reporting describes an intended mid-2026 implementation but gave no firm go-live date, and the checked live exam and registration pages still described the older form.
The practical upshot: the technical content (soil gas, pressure fields, fan and pipe sizing, installation, verification) is stable across both versions. What shifts is how the material is grouped and weighted. Study the engineering fundamentals deeply and the version question matters far less.
The Six Domains and Their Weights at a Glance
These six examination domains come from the announced blueprint. They are exam domains, not preparation-course time allocations, so do not assume a 28% course module on diagnostics.
| Domain | Name | Weight |
|---|---|---|
| 1 | General | 4% |
| 2 | Inspection | 13% |
| 3 | Diagnostics | 28% |
| 4 | System Design | 24% |
| 5 | ASD Mitigation System Installation | 23% |
| 6 | Post-mitigation | 8% |
Notice the concentration. Diagnostics, System Design, and Installation together carry 75% of the blueprint. General and Post-mitigation combined carry only 12%. A candidate who masters the middle three domains and is merely competent on the rest is positioned far better than one who spreads effort evenly. For a broader view of how demanding the material is, read How Hard Is the RMS Exam?
Domains 1 and 2: General and Inspection
Domain 1: General (4%)
The smallest domain covers foundational context: radon basics, the role of the specialist, and professional conduct. At 4% it rewards a quick, clean review rather than a long study block. Do not ignore it, though, because ethical and professional-conduct items are easy points if you have read the relevant terms and standards.
Domain 1: General
Low weight, low effort per point. Cover it early and move on.
- Basic radon science vocabulary and how radon enters buildings
- Professional and ethical responsibilities of a certified specialist
- Where the governing ANSI/AARST standards fit into everyday practice
Domain 2: Inspection (13%)
Inspection is where a specialist reads the building and the pre-mitigation data before touching any tools. Expect scenario thinking: given a foundation type, a set of observations, and a measurement result, what does it tell you about likely entry points and how hard the job will be?
Domain 2: Inspection
Connect what you see in the structure to what you will need to do about it.
- Identifying radon entry points: slab cracks, control joints, sump pits, floor drains, crawlspace soils, block walls, utility penetrations
- Evaluating pre-mitigation measurement results and their limitations
- Recognizing foundation types and the construction details that complicate sealing and suction
- Communicating findings and expectations to the client
The older legacy structure carried similar themes under headings such as identifying radon entry points and evaluating pre-mitigation measurement, so reference material built on the earlier scope still transfers well here.
Domain 3: Diagnostics (28%)
Diagnostics is the heaviest domain on the announced blueprint, and it is the one where hands-on reasoning separates strong candidates from memorizers. This is where you determine how well suction will communicate beneath the slab and what that means for system layout.
Domain 3: Diagnostics
Think like a technician troubleshooting an unknown sub-slab environment.
- Pressure-field extension: what it is, how it is tested, how to interpret communication readings, and what poor extension implies
- Sub-slab communication testing: the purpose of diagnostic suction tests and how results inform suction point placement and count
- Soil and aggregate considerations: how permeable fill, tight clay, and footings or interior walls change communication
- Airflow and pressure relationships: why suction and flow trade off, and how that shapes fan selection later
- Competing depressurization and combustion safety: recognizing building conditions that can affect system performance and safety
Study diagnostics as a decision chain: observation, test, interpretation, design implication. Exam items in this area are likely to reward candidates who can say what a given reading means and what to do next, not merely define terms. Because diagnostics feeds directly into design, plan to study these two domains back to back.
Domain 4: System Design (24%)
System Design converts diagnostic findings into a specification: where suction points go, what piping runs, what fan, and how the system exhausts. In the legacy blueprint's specialist section, designing the radon mitigation system was the single largest heading at 25% of that section, which hints at how central design thinking is to the specialist role.
Domain 4: System Design
Know the math and the rules, because you will be supplied with standards and formulas on the live exam but still have to apply them.
- Radon fan and pipe sizing: matching fan performance curves to expected static pressure and airflow, and understanding friction losses in piping
- Suction point selection: number, location, and pit size based on diagnostic results
- Piping layout: routing, slope for condensation drainage, support, and penetrations
- Exhaust and discharge requirements: termination location relative to windows, openings, and roof lines per the governing standards
- Alternatives to sub-slab depressurization: when other approaches apply and their limitations
- Electrical and monitoring components: disconnects, system-status indicators such as manometers or alarms
The standards NRPP currently lists for the exam are SGM-SF-2023 and MAH-2023. Make sure your study materials reference these editions. Work through numeric design problems by hand until the sizing logic feels automatic, then rehearse it with the on-screen calculator you will actually use.
Domain 5: ASD Mitigation System Installation (23%)
Active soil depressurization (ASD) installation is the physical craft: building the system as designed, safely and durably. The exam draws from installer competencies because the 2021 issuer launch explicitly folded installer competencies into the RMS examination. That is a key difference between the RMS and a standalone installer-level credential, which you can compare in our overview of the RMS certification.
Domain 5: ASD Mitigation System Installation
Know the sequence of work and the reason behind each step.
- Suction pit creation and sub-slab prep: excavation, pit sizing, and restoring the slab opening
- Sealing: sealants and methods for slab cracks, joints, sump covers, and other openings, and why sealing supports system performance
- Pipe installation: materials, joints, supports, fire-stopping and penetrations, and condensation management
- Fan installation: location restrictions, mounting, vibration and noise considerations, and electrical connection safety
- Jobsite safety: protective equipment, dust control, electrical and ladder hazards, and worker safety planning
- Labeling and homeowner information: system labels, monitoring devices, and documentation left at the property
At 23% this domain nearly matches System Design. If you come from a field background, you may find installation intuitive and design harder. If you come from an inspection or measurement background, expect the reverse. Be honest about which side you are weaker on and adjust.
Domain 6: Post-mitigation (8%)
After the system is running, the specialist verifies that it works and that the building remains safe. In the legacy structure, post-installation tasks and validating post-installation data appeared as distinct headings, and the new blueprint rolls the idea into a compact domain.
Domain 6: Post-mitigation
Short, but it ties the whole process together and shows up in scenario questions.
- Post-installation radon testing and interpreting results against action levels
- Verifying system operation, such as pressure or flow indicators and fan function
- Quality assurance and quality control practices
- Troubleshooting a system that is not delivering expected reductions
- Documentation, client communication, and follow-up
Troubleshooting questions often straddle this domain and Diagnostics. If a post-mitigation reading is high, the right answer usually traces back to a diagnostic or design cause. Reading across domains this way mirrors how real service calls unfold.
The Legacy Section Weights You May Still See
Older study materials, handbooks, and the issuer's 2021 launch describe the exam using two separate sections, each totaling its own 100%. These percentages are not a single combined whole-exam blueprint, and they should not be merged into one distribution. The older form is described in the May 2026 comparison as Part 1 and Part 2, with different item counts.
| Legacy installer sections | Weight within section | Legacy specialist sections | Weight within section |
|---|---|---|---|
| Communicate with the Client | 14% | Communicate Basic Radon Science | 9% |
| Identify Radon Entry Points | 17% | Evaluate Pre-Mitigation Measurement | 8% |
| Maintain Jobsite Safety | 15% | Design Radon Mitigation System | 25% |
| Implement Mitigation Installation Strategy | 30% | Validate Post-Installation Data | 12% |
| Perform Post-Installation Tasks | 17% | Troubleshooting System Problems / Implement Corrective Actions | 17% |
| Operate in an Ethical and Professional Manner | 7% | Develop / Maintain Worker Health and Safety Plan | 8% |
| Maintain Mitigation Quality Assurance Plan | 12% | ||
| Operate in an Ethical/Professional Manner | 9% |
Why does this matter? Because it explains a common source of confusion. The specialist-section tasks total fewer items than the whole exam, since the installer competencies sit in the other section. The older handbook's RMS table labels 150 questions without clearly separating those denominators, which is a limitation to keep in mind when reading older guides. The eight specialist headings alone are not a complete whole-exam blueprint.
Exam Mechanics, Fees and Prerequisites
Question count and timing: the 165 versus 175 conflict
The live operational page states 165 total questions: 150 scored at one point each, plus 15 unidentified unscored trial questions, over three hours, effective October 1, 2024. The May 2026 update instead specifies 175 total, with 160 scored plus 15 pilot questions, still three hours. Because the active-form conflict is unresolved, we do not give one definitive number. Either way, you cannot tell which items are unscored, so treat every question as if it counts. Course hours, lab work, and field experience are not exam time.
Delivery and conduct
- Computer-delivered through Certiverse with live remote proctoring on the operational route
- Photo ID and a room scan are required; the session is monitored and recorded
- Supplied resources include ANSI/AARST standards, an on-screen calculator, and formula resources
- One break of up to five minutes is allowed with proctor permission
- Purchase must be scheduled and completed within 30 days
- Retakes require a 30-day wait, with no more than four attempts in 12 months
NRPP describes a criterion-referenced competent-performance standard set through expert judgment, and a current numeric cutoff is not publicly specified. Do not import another organization's percentage threshold. For the full picture, see RMS passing score.
Cost and prerequisites at a glance
| Item | Operational route |
|---|---|
| Exam fee | USD 175 per attempt |
| Initial two-year certification | USD 275 |
| Exam plus initial certification | USD 450, before training and other costs |
| Renewal | USD 275 every two years |
| Required coursework | NRPP-approved 16-hour measurement course plus 24-hour RMS mitigation course, valid for two years |
| After passing | Apply within one year of passing and agree to ethics and terms |
The announced revision instead specifies a 32-hour mitigation course that includes the requisite measurement content, plus lab and field experience, without the former separate 16-hour measurement course. Field-assessment implementation was still being developed, so no field-hour minimum is established here. Passing the exam alone does not confer certification, and state licensing is separate. Details live in our guides to RMS requirements and RMS certification cost.
Renewal: 12 versus 24 CE hours
The operational term is two years with 12 continuing education hours, at least eight Category I and no more than four Category II, with the mandatory four-hour mitigation standards overview included in the 12. The announced replacement requires 24 CE hours per two years, including four standards-review hours, and introduces work-sample and experience documentation. Which applies to you depends on your renewal cycle, so confirm with NRPP.
Sequencing Your Prep by Domain
Because the weights are lopsided, order matters more than total hours. Here is one way to sequence the material, built around the dependency between domains rather than generic study habits.
Foundations and Inspection (Domains 1 and 2)
- Review radon science vocabulary and professional conduct quickly
- Map entry points by foundation type and practice reading pre-mitigation data
Diagnostics into Design (Domains 3 and 4)
- Work pressure-field extension and communication test interpretation first
- Then do fan and pipe sizing problems that depend on those results
- Practice locating provisions in the supplied standards
Installation (Domain 5)
- Walk through the build sequence from pit to fan to labeling
- Review jobsite safety and sealing rationale
Post-mitigation and mixed review (Domain 6)
- Cover verification, QA/QC, and troubleshooting chains
- Take timed mixed sets in the RMS practice test and revisit the weakest domain
Dedicated materials help here. Pair this sequence with the RMS study guide and the one-page RMS cheat sheet for last-day review. You can also drill each domain in the main practice test to see where you actually stand before booking the exam.
Key Takeaway
Put roughly three-quarters of your effort into Diagnostics, System Design, and Installation, and study the first two together because design decisions depend directly on diagnostic readings.
Frequently Asked Questions
The announced NRPP blueprint lists six: General, Inspection, Diagnostics, System Design, ASD Mitigation System Installation, and Post-mitigation. Older materials describe separate installer and specialist sections instead, so confirm which form applies to your booking.
Diagnostics at 28%, followed by System Design at 24% and ASD Mitigation System Installation at 23%. Together those three account for 75% of the announced blueprint.
It depends on the active form. The live operational page states 165 total (150 scored plus 15 unscored trial items), while the May 2026 update specifies 175 total (160 scored plus 15 pilot items). Both allow three hours, and the conflict was unresolved when we checked.
No. Outside books, notes, and personal calculators are prohibited. The exam supplies ANSI/AARST standards, an on-screen calculator, and formula resources, so practice using those tools.
The operational exam fee is USD 175 per attempt and initial two-year certification is USD 275, totaling USD 450 before training and other costs. For a fuller breakdown, see our RMS certification cost guide, and weigh the investment in Is the RMS certification worth it?