- The Number: 70% of 50 Questions
- How the Score Is Delivered
- What the Questions Draw On: Four Reference Areas
- 70% Threshold vs. the Reported Cohort Result
- What Has to Happen Before You Can Test
- What a Miss Costs: Fees and Retakes
- Allocating Prep Time Across the Four Reference Areas
- Passing-Score Claims to Treat With Caution
- After You Pass: Validity and Renewal
- Frequently Asked Questions
- The Council-certified Structural Mold Investigator exam has 50 multiple-choice questions and a stated passing score of 70%.
- You get two hours, closed book, with results delivered immediately on screen and by email.
- The 70% threshold is not the same thing as the reported 91% cohort pass ratio for 2025.
- Study the full ACAC reference list; highlighted study-guide sections do not mark the boundary of examinable material.
The Number: 70% of 50 Questions
The passing score for the Council-certified Structural Mold Investigator (CSMI) exam, administered by the American Council for Accredited Certification (ACAC), is 70%. The exam consists of 50 multiple-choice questions with at least four answer choices each, delivered in a closed-book, two-hour session.
A 70% threshold on a 50-question exam works out to 35 correct answers, which means you can miss up to 15 questions and still pass. That arithmetic is a straightforward reading of the published figures. ACAC's materials state the percentage; they do not publish a scaled-score conversion, so treat "35 of 50" as a planning shorthand rather than an official cut-score statement, and confirm the operative scoring details with ACAC if precision matters to you.
How the Score Is Delivered
Results are immediate. When you finish, you see your outcome electronically, and a copy follows by email. There is no multi-week wait for a score report, which also means your first indication of a miss arrives while you are still at the testing center or in your proctored online session.
Two format details affect how you experience the scoring:
- Randomized order. Both question order and answer order are randomized. You cannot rely on memorized answer positions, and a classmate's sitting may look different from yours.
- Closed book. The reference works are for study, not for the exam room. Two hours for 50 questions is a comfortable pace for prepared candidates, roughly 2.4 minutes per question, so the time limit is rarely the binding constraint. Knowledge gaps are.
The two-hour figure is the written examination duration. It is not a statement about course length or practical-assessment hours, so do not read it as a measure of how much training the credential implies.
What the Questions Draw On: Four Reference Areas
ACAC's CSMI study guide organizes preparation around four references. These are unweighted preparation categories, not four official weighted exam domains. ACAC has not published percentage weights per area, so any claim that "Domain 3 is 40% of the test" is invented. The body of knowledge broadly addresses structural mold sources, potential health effects, and methods of locating and identifying microbial contamination. For a deeper walk through each area, see the CSMI exam domains guide.
AIHA, Field Guide
The AIHA Field Guide for the Determination of Biological Contaminants (second edition, 2005) is the field-investigation reference.
- Methods of locating and identifying microbial contamination
- Sampling approaches and how results are interpreted in context
- Recognizing how sample data relates to building conditions
ACGIH, Bioaerosols: Assessment and Control
The ACGIH reference (first edition, 1999, or second edition, 2024) covers assessment and control of airborne biological contaminants.
- Bioaerosol assessment concepts and strategy
- Control approaches and the reasoning behind them
- Health-effects education at the level a mold investigator needs (this is education about potential effects, not medical diagnosis)
IICRC, S500-2021
ANSI/IICRC S500-2021 (fifth edition) is the standard for professional water damage restoration, and moisture is the engine behind structural mold.
- Water-damage categories and classes and why they matter to microbial growth
- Drying principles and building-system behavior
- The public study guide cites reading locations including sections A, B, and 1 through 8, plus glossary pages 99-118
IICRC, S520
The ANSI/IICRC S520 standard covers professional mold remediation. The references list S520-2015 with R520-2015 (third editions) or S520-2024 (fourth edition).
- Conditions 1, 2, and 3 concepts and how they frame a contamination assessment
- Remediation process logic from an investigator's perspective
- Terminology you must read precisely under closed-book conditions
70% Threshold vs. the Reported Cohort Result
These two numbers answer different questions and are easy to confuse:
| Figure | What it is | What it is not |
|---|---|---|
| 70% passing score | The per-candidate threshold you must reach on the 50-question exam | A statement about how many people pass |
| 91% (29 of 32 in 2025) | A cohort figure ACAC reportedly rounded from 29 passes across 32 exam administrations in its 2025 Exam Pass Ratio report | A first-attempt rate, a guarantee for you, or a figure freshly reverified for this article |
Treat the cohort figure carefully. It is preserved from a prior review; the source PDF could not be re-fetched when this article was prepared, although ACAC's current-statistics page still links the report. The report is described as including retakes and state-licensing-only exams, so it is not a clean first-attempt measure. The sample is also small, only 32 administrations, so one or two results move the percentage noticeably. For the fuller discussion, read what the CSMI pass-rate data shows, and for a candid look at difficulty, see how hard the CSMI exam is.
What Has to Happen Before You Can Test
Passing the exam is one step in a sequence. The eligibility path involves:
- Attestation of current employment in structural mold investigation.
- Application and identity verification.
- A successful examination.
- Certification-board approval.
No minimum experience duration and no compulsory preparatory course are specified, and CSMI applicants are explicitly exempt from project sheets. But current employment is still required, so it would be wrong to describe this credential as having no prerequisites. The full breakdown is in CSMI requirements: eligibility and how to qualify.
Testing is provided by Kryterion, Inc., either at authorized testing centers or through secure online video proctoring. An instructor-proctored vocational option is available by arrangement. On timing, the current online application gives six months, while the handbook retains 90-day and notarized-paper wording. Follow the current application instructions and confirm the operative deadline directly with ACAC. For scheduling logistics, see CSMI exam dates, windows, and scheduling.
What a Miss Costs: Fees and Retakes
| Item | Fee (USD) |
|---|---|
| Examination | $100 |
| Certification | $300 |
| Total, initial | $400 |
| Retake | $100 |
| Renewal | $300 |
The retake fee is the number that matters most for passing-score strategy. Missing 70% costs you $100 plus the time to prepare again, not the full $400, because the certification fee attaches to the credential rather than to each attempt. That is a modest penalty compared with many professional exams, but it is still money and scheduling friction you can avoid with focused preparation. Current fee details live on ACAC's fees page, and the complete picture is in the CSMI certification cost breakdown.
Allocating Prep Time Across the Four Reference Areas
Because the four areas are unweighted, a sensible plan distributes effort by how foundational each is and how dense the reading is, not by invented percentages. One reasonable ordering, offered as a suggestion rather than an ACAC requirement:
IICRC S500-2021
- Moisture and water-damage fundamentals come first because they explain why structural mold occurs at all
- Work through sections A, B, and 1-8 plus the glossary, then read beyond them
IICRC S520
- Learn the remediation vocabulary precisely; closed-book questions reward exact terminology
- Stay with one edition throughout so definitions do not blur
AIHA Field Guide
- Focus on locating and identifying contamination and on interpreting sampling results in context
- Write your own scenario questions; interpretation is learned by applying it
ACGIH Bioaerosols + review
- Cover assessment, control, and health-effects education
- Finish with timed 50-question sets across all four areas
The point of that ordering is dependency: moisture understanding supports remediation logic, which supports sampling interpretation. Adjust it to your own background. A candidate with years of field sampling experience might compress the AIHA block and spend longer on the standards. For a fuller plan, see the CSMI study guide for first-attempt success, and when you want exam-style repetition, use the CSMI practice test. A one-page recap of terminology is available in the CSMI cheat sheet.
Key Takeaway
Aim well above 70% in practice. Your practice scores are an imperfect proxy for the real exam, and a comfortable margin over the threshold protects you against unfamiliar phrasing and the randomized question order. Review every missed question by tracing it back to the specific reference section it came from, not just the correct answer.
Passing-Score Claims to Treat With Caution
Several kinds of third-party content circulate around this credential, including flashcard sets, exam-prep marketplaces, and document-sharing sites. Their existence does not verify their quality.
- Pooled material. Some content mixes questions from other mold credentials or from different credentials that happen to share the same acronym. The CSMI covered here is specifically the Council-certified Structural Mold Investigator from ACAC. Material built for CMI or CMC candidates is not a CSMI question bank.
- "Actual exam" claims. Listing access to a document tells you nothing about whether its contents are accurate, current, or genuinely representative of the exam.
- Guaranteed-pass advertising. No preparation vendor controls your result. ACAC publishes a policy on independent preparation courses; read it before paying for any program, and remember that course completion alone does not confer ACAC certification.
- Accreditation confusion. This vocational designation is not CESB-accredited, unlike the separate CMI and CMC credentials, and passing an exam solely for state licensing does not confer ACAC certification. Check ACAC's accreditation page if this distinction matters for your jurisdiction or employer.
If you are comparing the CSMI to other mold credentials, the differences in scope and accreditation are substantial, and it is worth reading the official program pages before choosing a path. Wondering what the credential even covers at a basic level? Start with what CSMI certification is.
After You Pass: Validity and Renewal
The credential is valid for two years. Current renewal procedures require an updated photo and 40 recertification credits, split into 10 for continued field activity and 30 professional-development hours. Keep supporting records, because they can be audited. The renewal fee is $300. Certificants are also bound by the ACAC Code of Conduct.
Whether the investment pays off depends on your situation. Mold inspection is an occupation with its own pay patterns, and no published figure here isolates a pay premium caused by holding the certification. For an honest look at earnings and return, see the CSMI salary guide and the analysis of whether the CSMI is worth it, and for the job side, CSMI jobs.
Frequently Asked Questions
The passing score is 70%. The exam has 50 multiple-choice questions, so 70% corresponds to 35 correct answers by simple arithmetic, though ACAC states the percentage rather than a scaled-score conversion.
No. The reported 91% reflects 29 passes from 32 exam administrations in 2025, as preserved from a prior review of ACAC's pass-ratio report. It reportedly includes retakes and state-licensing-only exams, so it is not a first-attempt rate and not a guarantee for any individual.
You have two hours, and the exam is closed book. You see your result immediately on screen, and it is also emailed to you.
A retake costs $100. The initial total is $400, made up of the $100 examination fee and the $300 certification fee. Confirm current amounts on ACAC's fees page before paying.
No percentage weights have been published or verified. The four areas (AIHA Field Guide, ACGIH Bioaerosols, IICRC S500-2021, and IICRC S520) are unweighted preparation categories, and ACAC expects study of the full references rather than only highlighted sections.
The passing score itself is simple: 70% on 50 questions. The harder work is mastering four dense references well enough to clear it in a closed-book setting, so build your preparation around the references themselves and use the CSMI exam prep practice questions to check your readiness before you schedule.