- Confirm You Have the Right CMC
- Exam Snapshot: Format, Scoring, and Logistics
- Fees, Timeline, and Renewal at a Glance
- Eligibility Pathways in One Table
- The Six Official Domains, Condensed
- Reference Books and Edition Alternatives
- What the 2025 Pass Data Does and Does Not Say
- Where ACAC's Own Sources Disagree
- Mapping the Domains to a Study Calendar
- Quick Answers
- The exam is 120 multiple-choice questions in three hours, closed book, with a 75% passing score.
- ACAC publishes six unweighted domains, so no domain can be called the heaviest.
- Initial cost is $500 for a two-year term: $100 exam plus $400 certification.
- Renewal needs 40 RCs: 10 for field activity and 30 for professional development.
Confirm You Have the Right CMC
Before memorizing anything, confirm which credential this sheet covers. "CMC" is shared by several unrelated certifications in management, nursing, and other fields. This cheat sheet covers only the Council-certified Microbial Consultant credential, issued by the American Council for Accredited Certification (ACAC) through its CMC Certification Board. The program carries accreditation from the Council for Engineering and Scientific Specialty Boards (CESB).
If you need a plain-language orientation first, see What Is CMC Certification? or What Does CMC Stand For?. If you are ready to test your recall, the main practice test site is built around this specific exam.
Exam Snapshot: Format, Scoring, and Logistics
| Item | What ACAC specifies |
|---|---|
| Question count | 120 multiple-choice questions |
| Answer options | At least four per question |
| Time | Three hours, computer-delivered |
| Book policy | Closed book |
| Passing score | 75%, set using a Modified Angoff method |
| Scored vs. unscored items | Not published |
| Practical component | None described |
| Delivery | Testing center or online video proctoring, scheduled through ACAC |
| Results | Immediate electronic score, with results emailed |
Test-day mechanics worth memorizing
- Question order: The handbook describes the same question set with randomized question and answer order. Adaptive testing is not described.
- Calculator: Permission is unverified. Confirm with ACAC when you schedule rather than assuming either way.
- Testing-center ID: Bring two government-issued IDs, including one photo ID.
- Online setup: You supply the computer, an approved webcam, and a private location. ACAC specifies at least 2 Mbps upload and download and excludes phones and tablets.
- Arrival: The current Examinations page says 15 minutes early; the handbook says 30. Plan for the longer buffer.
The 75% passing score and the 94% pass ratio are different things. One is the cut score on your exam; the other is a historical outcome statistic. For a deeper treatment, read CMC Passing Score 2026.
Fees, Timeline, and Renewal at a Glance
| Cost item | Amount (USD) |
|---|---|
| Examination fee | $100 |
| Certification fee | $400, including $100 nonrefundable processing |
| Total for initial two-year term | $500 |
| Retake | $100 |
| Renewal | $400 |
ACAC publishes no separate member and non-member fee schedule. The fee source is ACAC's Fees and Payments page, so check it again before paying. For a fuller breakdown, see CMC Certification Cost 2026.
Renewal rules to retain
- Certification is valid for two years.
- The current Recertification Procedures call for 40 RCs: 10 for continued field activity and 30 for professional development during the term.
- You submit an attestation and retain evidence in case of audit. A current photo is requested.
Eligibility Pathways in One Table
ACAC allows three routes. In each, the experience must be documented microbial sampling or consulting experience, and candidates must demonstrate designing, conducting, and interpreting sampling regimens.
| Education background | Experience required |
|---|---|
| Related four-year postsecondary degree, or 30 qualifying college credits | Four years of documented microbial sampling |
| Related two-year degree, or 15 qualifying credits | Six years of documented microbial sampling |
| High school diploma or GED | Eight years of consulting experience in microbial sampling |
- Qualifying fields include microbiology, engineering, science, architecture, and industrial hygiene. ACAC's FAQ defines qualifying coursework and excludes social sciences.
- You must submit four project sheets, applicable transcripts, and experience verification.
- The handbook says experience should come from Building Sciences, Microbiology, and Microbial Risk Analysis. Treat that as guidance on the nature of your experience, not as a separately enforced three-area rule.
- No mandatory preparation course or minimum training-hour requirement is published.
The Six Official Domains, Condensed
ACAC's current linked domain chart (approved February 21, 2024) lists six domains. No percentage weights are published, so any site claiming a "heaviest domain" is guessing. Some third-party resources split practice material into roughly equal categories; those are publisher choices, not official weights. Because the chart's numbered columns describe subdomains, do not confuse them with extra domains. For the full walk-through, see CMC Exam Domains 2026.
Domain 1: Scientific knowledge of biological agents
The biology underlying everything else. Expect questions on what organisms are, how they grow, and what conditions favor them.
- Fungi, bacteria, and other biological agents relevant to indoor environments
- Growth requirements and moisture relationships
- Bioaerosol behavior and why airborne and surface results can differ
Domain 2: Potential health effects and risks associated with exposure
Connecting exposure to human outcomes, with appropriate caution about what evidence can and cannot show.
- Exposure pathways and susceptible populations
- Risk concepts versus causal certainty
- Communicating limits of what sampling data can say about health
Domain 3: Principles of Microbial Investigation
The structured approach to figuring out whether a problem exists and where it comes from.
- Building-science context: moisture sources, pathways, and building envelope
- Visual and instrument-assisted assessment
- Forming hypotheses and deciding what to sample, if anything
Domain 4: Principles of Microbial Sampling
The heart of the credential's eligibility requirement: designing, conducting, and interpreting sampling regimens.
- Sampling design, including controls and outdoor comparison
- Method selection and equipment calibration
- Data limitations and defensible interpretation
Domain 5: Principles of Microbial Remediation
What remediation should accomplish, how it is documented, and how success is verified.
- Containment, removal, and drying concepts, tied to the IICRC S520 reference
- Remediation documentation
- Post-remediation verification logic
Domain 6: Health & Safety
Easy to overlook because the shorter handbook text omits it as a standalone topic, but the formal chart includes it as a full domain.
- Respiratory protection program basics and respirator selection
- Worker and occupant protection during investigation and remediation
- Regulatory guidance cited in the OSHA and NIOSH references
Reference Books and Edition Alternatives
The handbook lists the following references. Where it allows alternatives, either edition is acceptable to name in your preparation, but the listing does not establish an exam revision date.
| Reference | Edition(s) listed |
|---|---|
| ACGIH, Bioaerosols: Assessment and Control | First edition (1999) OR second edition (2024) |
| AIHA, Field Guide for the Determination of Biological Contaminants | Second edition (2005) |
| ANSI/IICRC S500 | 2021, fifth edition |
| ANSI/IICRC S520 and R520 | S520-2015 and R520-2015, third editions, OR S520-2024, fourth edition |
| OSHA, Small Entity Compliance Guide for the Respiratory Protection Standard | 2011 |
| NIOSH, Respirator Selection Logic | 2004 |
Key Takeaway
The handbook warns that its study-guide sections and page references are examples, not exhaustive exam preparation, and that the exam assumes comprehensive knowledge of the listed references. Read these sources in full instead of studying only the sample pages. See the CMC study guide for a structured approach.
What the 2025 Pass Data Does and Does Not Say
ACAC's 2025 Exam Pass Ratio reports 94%, which is 16 passes from 17 attempts. Treat this carefully:
- The sample is tiny. One additional failure would change the percentage noticeably.
- Attempts include retakes and state-licensing-only candidates, so this is not first-attempt-only data.
- No 2026 rate has been verified.
- ACAC's accredited certification activity as of December 31, 2025 lists 17 applicants, 99 recertifications, and 288 current CMC certifications. These counts describe the credential's size, not exam difficulty.
Some third-party pages claim ACAC does not publish CMC pass rates; that is contradicted by ACAC's 2025 report. For interpretation, read CMC Pass Rate 2026 and How Hard Is the CMC Exam?. Note too that applicants are screened through experience review and board approval before they ever sit the exam, which shapes who reaches the test.
Where ACAC's Own Sources Disagree
Good cheat sheets flag uncertainty. These are the conflicts to verify with ACAC before you rely on any one figure:
| Topic | Source A | Source B |
|---|---|---|
| Application window | Current application page: six months including the exam; board meets every four to six weeks | Handbook: 90 days, with notarized forms and employer affidavits |
| Arrival time | Examinations page: 15 minutes early | Handbook: 30 minutes early |
| Renewal credits | Recertification Procedures: 40 RCs (10 field activity, 30 professional development) | Handbook: general 40-RC wording; program page: 20 professional-development hours per year |
| Body of knowledge | Formal domain chart: six domains including Health & Safety | Handbook: shorter five-topic text without standalone Health & Safety |
In each case, the more specific and more current document (the procedures page, the examinations page, the formal domain chart) is the safer working assumption, but a quick confirmation with ACAC costs nothing.
Mapping the Domains to a Study Calendar
This is the one place generic planning belongs, and it is tied to the credential's structure. Because no domain is officially weighted, give each domain real time, and front-load the biology that later domains depend on. Sampling gets the longest block because the eligibility rules themselves center on designing, conducting, and interpreting sampling regimens.
Domains 1 and 2
- Biological agents, growth conditions, and exposure-to-health reasoning
- Start the ACGIH bioaerosols reference
Domains 3 and 4
- Investigation workflow, then sampling design, methods, calibration, and interpretation limits
- Work through the AIHA field guide
Domains 5 and 6
- S500 and S520 remediation principles, documentation, and verification
- OSHA respiratory protection guide and NIOSH respirator selection logic
Timed integration
- Full-length closed-book practice at 120 questions in three hours
- Review misses by domain, not by question number
Use a timed run to practice pacing: three hours for 120 questions averages out to about a minute and a half per item. Try the CMC practice tests to build that rhythm.
Quick-Hit Facts for the Night Before
- Issuer: ACAC; program accredited by CESB.
- 120 questions, three hours, closed book, 75% to pass.
- Six domains, no published weights.
- $500 initial ($100 exam plus $400 certification); $100 retake; $400 renewal.
- Two-year term; 40 RCs to renew.
- Four project sheets plus transcripts and experience verification.
- Bring two government-issued IDs (one with a photo) to a testing center; online candidates need a webcam and at least 2 Mbps.
No reliable salary survey specific to ACAC CMC holders has been verified, so be skeptical of any precise earnings figure attached to this credential. To weigh the investment honestly, read Is the CMC Certification Worth It?, the CMC salary guide, and CMC jobs.
Quick Answers
None can be identified. ACAC's domain chart lists six domains without percentage weights, so prepare across all six rather than betting on one.
No. ACAC publishes no mandatory preparation course or minimum training-hour requirement. It does maintain a provider directory, but listing there is not a requirement for candidates.
The $500 total is a $100 examination fee plus a $400 certification fee (including $100 nonrefundable processing), covering the initial two-year term.
Not necessarily. It reflects 16 passes from 17 attempts in 2025, includes retakes and licensing-only candidates, and comes from a very small group of pre-screened applicants.
Renew every two years for $400, with 40 RCs: 10 for continued field activity and 30 for professional development, plus an attestation and retained evidence in case of audit.