- The Short Answer: What a CMC Actually Is
- Who Issues the Credential and Why That Matters
- What a Council-certified Microbial Consultant Does
- The Six Exam Domains in Plain Language
- Who Qualifies to Apply
- The Exam: Format, Logistics and Fees
- The Reference Library Behind the Exam
- CMC Versus Other Credentials Sharing the Acronym
- After You Pass: Validity, Renewal and Career Use
- A Domain-Ordered Study Sequence
- Frequently Asked Questions
- CMC here means Council-certified Microbial Consultant, issued by ACAC's CMC Certification Board and accredited by CESB.
- The exam is 120 multiple-choice questions in three hours, closed book, with a 75% passing score.
- The initial two-year term costs $500 total: a $100 exam fee plus a $400 certification fee.
- Six official domains apply, from biological agents through Health & Safety, and no percentage weights are published.
The Short Answer: What a CMC Actually Is
A CMC, in the context of this site, is a Council-certified Microbial Consultant: a professional who has been certified to design, conduct and interpret microbial sampling regimens, and to advise on investigation and remediation of microbial contamination in the built environment. It is a peer-reviewed, experience-based professional credential, not a weekend course certificate.
The acronym is crowded. Other well-known credentials in unrelated fields also abbreviate to "CMC," and search results blend them together constantly. Everything on this page concerns only the ACAC credential. If you are weighing whether it fits your career, our overview at What Is CMC Certification? covers the same ground from a slightly different angle, and What Does CMC Stand For? addresses the naming question directly.
Who Issues the Credential and Why That Matters
The credential is issued by the American Council for Accredited Certification (ACAC) through its CMC Certification Board. The program is accredited by the Council for Engineering and Scientific Specialty Boards (CESB), an accreditation body for engineering and scientific specialty certifications. Exam delivery is handled through Kryterion, Inc., and scheduling runs through ACAC.
Why does the issuer matter? Three reasons:
- Independence. The credential is not tied to a training vendor. ACAC lists a provider directory of preparation courses, but no preparation course is mandatory and no minimum training-hour requirement is published.
- Peer review. Certification requires unanimous board approval of your application, so the process evaluates documented field work, not just exam performance.
- Accreditation. CESB accreditation of the program gives employers and clients an external reference point for the rigor of the process.
What a Council-certified Microbial Consultant Does
The certification handbook frames the expected experience around designing, conducting and interpreting sampling regimens. In practice, that means a CMC works on questions such as: Is there a microbial problem in this building? How should we sample to find out? What do the results actually say, and what do they not say? How should remediation be scoped and verified?
Typical settings include building sciences work, indoor environmental consulting, industrial hygiene practices, and engineering or architectural firms that handle moisture and indoor air quality investigations. The handbook says qualifying experience should come from Building Sciences, Microbiology and Microbial Risk Analysis, although that wording is guidance rather than a mandatory three-area checklist.
Where the credential gets used
- Writing sampling plans that match the question being asked, rather than defaulting to a standard protocol
- Interpreting laboratory results with an honest account of their limits
- Documenting remediation scope and confirming outcomes after remediation
- Advising on respiratory protection and worker safety during investigation and cleanup
For a closer look at hiring patterns and role types, see CMC Jobs. Salary conversations deserve caution: no reliable salary survey specific to ACAC CMC holders has been verified, so treat any precise figure you see online with suspicion. Our CMC Salary Guide discusses how to evaluate earnings claims without relying on unrelated aggregates.
The Six Exam Domains in Plain Language
ACAC's current formal domain chart (approved February 21, 2024) lists six domains. These are official exam objectives, not a provider's curriculum. Importantly, no percentage weights are published, so you cannot honestly say which domain is "most heavily tested." Third-party sites that assign equal 20% allocations are describing their own practice-resource categories, not official blueprints.
Domain 1: Scientific knowledge of biological agents
The biology underneath the work: what organisms you are dealing with and how they behave in buildings.
- Fungi, bacteria and related agents relevant to indoor environments
- Growth conditions, moisture relationships and amplification
- How biological material becomes airborne or settles on surfaces
Domain 2: Potential health effects and risks associated with exposure
The link between exposure and human outcomes, including the uncertainty that surrounds it.
- Exposure pathways and routes
- Susceptible populations and risk characterization
- What evidence can and cannot support about causation
Domain 3: Principles of Microbial Investigation
How to structure an investigation from first complaint to defensible conclusion.
- Visual and moisture assessment, building history and hypothesis development
- Deciding whether sampling is warranted at all
- Documenting findings in a way a client or third party can follow
Domain 4: Principles of Microbial Sampling
The technical heart of the credential, matching directly to the "design, conduct and interpret" requirement.
- Air, surface and bulk sampling approaches and their trade-offs
- Equipment use, calibration and sample handling
- Controls, comparison locations and limitations of data
Domain 5: Principles of Microbial Remediation
What good remediation looks like and how success is verified.
- Containment, removal and cleaning principles
- Remediation protocols and documentation
- Post-remediation verification and clearance reasoning
Domain 6: Health & Safety
Protecting workers and occupants during investigation and remediation.
- Respiratory protection program concepts and respirator selection logic
- Hazard recognition during field work
- Regulatory and guidance context for worker protection
One detail trips up candidates: the handbook's shorter body-of-knowledge text lists five topics and omits Health & Safety as a standalone item, while the linked formal chart includes it as Domain 6. Study to the six-domain chart. For a deeper walk through each area, read CMC Exam Domains: Complete Guide to All 6 Content Areas.
Who Qualifies to Apply
ACAC offers three pathways, and the common thread is documented microbial sampling experience. Qualifying fields include microbiology, engineering, science, architecture and industrial hygiene. ACAC's FAQ defines what counts as qualifying college coursework and excludes social sciences.
| Pathway | Education | Documented Experience |
|---|---|---|
| Four-year route | Related four-year degree, or 30 qualifying college credits | Four years of microbial sampling |
| Two-year route | Related two-year degree, or 15 qualifying credits | Six years |
| Experience route | High school diploma or GED | Eight years of consulting experience in microbial sampling |
What the application package includes
- Four project sheets documenting your work
- Applicable transcripts
- Experience verification, with email verifications handled through the online forms
- Demonstration that you have designed, conducted and interpreted sampling regimens
A licensing-only exam result does not by itself confer CMC certification. Our CMC Requirements guide goes deeper on documenting experience and avoiding common application mistakes.
The Exam: Format, Logistics and Fees
The examination is a three-hour, computer-delivered, closed-book written exam with 120 multiple-choice questions, each with at least four answer options. The passing score is 75%, set using a Modified Angoff method, which involves subject-matter experts judging how a minimally competent candidate would perform on each item. ACAC does not publish how many questions are scored versus unscored. No separate practical assessment is described, and adaptive testing is not described either.
Question and answer order is randomized, scores appear immediately on screen, and results are emailed. Calculator permission is unverified, so check before exam day rather than assuming.
Fees at a glance
| Item | Amount (USD) |
|---|---|
| Examination fee | $100 |
| Certification fee (includes $100 nonrefundable processing) | $400 |
| Initial two-year term total | $500 |
| Retake | $100 |
| Renewal | $400 |
No separate member versus non-member fee schedule is published. The full breakdown, including how the nonrefundable processing portion works, is in CMC Certification Cost: Complete Pricing Breakdown.
Testing-day mechanics
- Testing center: bring two government-issued IDs, including one with a photo. The issuer's current exams page specifies arriving 15 minutes early, while the handbook says 30, so plan for the longer window.
- Online proctoring: supply your own computer, an approved webcam and a private location. ACAC specifies at least 2 Mbps upload and download speeds and excludes phones and tablets.
For passing-score mechanics see CMC Passing Score, and for scheduling windows see CMC Exam Dates.
Reading the pass-rate data carefully
ACAC's 2025 Exam Pass Ratio reports 94%, with 16 passes from 17 attempts. Two cautions apply. First, the sample is tiny, so one additional failure would shift the percentage noticeably. Second, attempts include retakes and state-licensing-only candidates, so this is not first-attempt-only data, and no 2026 rate has been verified. Also keep the concepts separate: the pass rate describes what share of candidates passed; the 75% passing score is the threshold you must reach on the exam. More context lives in CMC Pass Rate: What the Data Shows, and How Hard Is the CMC Exam? discusses what the numbers do and do not say about difficulty.
The Reference Library Behind the Exam
The handbook lists specific references that the exam assumes you know comprehensively. It also warns that its selected study-guide sections and page references are examples, not an exhaustive prep plan. In other words, skimming the highlighted pages is not a strategy.
- 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: 2015 third editions, or S520-2024, fourth edition
- OSHA Small Entity Compliance Guide for the Respiratory Protection Standard (2011)
- NIOSH Respirator Selection Logic (2004)
The handbook's "or" alternatives for the Bioaerosols and S520 editions do not establish an exam revision date, and no separately labeled 2026 exam version has been verified. Listing a reference also does not mean you get access to the full paid books; budget time and money to obtain the editions you plan to study from. Notice how these references map to the domains: bioaerosols and field-guide material support Domains 1, 3 and 4; the IICRC standards anchor Domain 5; OSHA and NIOSH documents anchor Domain 6.
CMC Versus Other Credentials Sharing the Acronym
Within ACAC itself, the CMC sits alongside a related investigator-level credential, and the two exams share a domain chart document (the CMC and CMI Examinations chart). If you are comparing the two, read the issuer's own materials for current scope and prerequisites rather than relying on summaries.
Beyond ACAC, be careful with third-party material:
- Practice sites may use the title "CMC" for content that has nothing to do with microbial consulting, including business-management scenarios.
- Some provider courses are mold-inspector training with their own licensing exams. A provider's mold-inspector exam must not be substituted for the ACAC CMC exam, and its course hours do not replace ACAC's requirements.
- Practice-test settings such as a 50-question, 60-minute mock describe a publisher's resource, not the official 120-question, three-hour exam.
Key Takeaway
Verify every study resource against three anchors: ACAC as issuer, six official domains including Health & Safety, and the 120-question, three-hour, 75% format. A resource that fails any of the three needs extra scrutiny.
After You Pass: Validity, Renewal and Career Use
Certification lasts two years. Current recertification procedures specify 40 recertification credits (RCs): 10 for continued field activity and 30 for professional development during the term. You attest to them and retain evidence in case of audit, and ACAC requests a current photo. The renewal fee is $400.
Be aware that the handbook uses a more general 40-RC description and the program page mentions 20 professional-development hours per year, so the wording differs across sources. Follow the current Recertification Procedures page and keep documentation from the first day of your term.
As of December 31, 2025, ACAC's activity report lists 17 applicants, 99 recertifications and 288 current CMC certifications. That is a small, specialized community, which says something about the niche nature of the credential. It is not a measure of search demand or job-market size. Whether the investment pays off for you depends on your employer, client base and market, so work through Is the CMC Certification Worth It? using your own numbers.
A Domain-Ordered Study Sequence
Because the exam spans science, field method and safety, sequencing matters more than hours logged. This is the one place for generic planning advice, tied directly to the domains: build the science first, then the method, then the safety layer, and finish by practicing integrated questions.
Domains 1 and 2: the science
- Read the Bioaerosols reference for agent behavior and exposure concepts
- Build a one-page map of exposure pathways and health-effect uncertainty
Domains 3 and 4: investigation and sampling
- Work through the AIHA field guide, focusing on sampling design, controls and result limitations
- Write sample plans for scenarios you have actually encountered, then critique them
Domains 5 and 6: remediation and safety
- Study S500, S520 and R520 for remediation principles and verification logic
- Review OSHA and NIOSH respirator guidance until selection logic is automatic
Integration
- Take timed mixed-domain practice sets on the main practice test site
- Review misses by domain, then return to the source reference
For a fuller plan, see the CMC Study Guide, and keep the CMC Cheat Sheet handy for last-week review. If you are unsure which resources deserve your time, CMC Training discusses preparation options, and our practice exam platform offers questions aligned to the six official domains.
Frequently Asked Questions
It stands for Council-certified Microbial Consultant, a credential issued by the American Council for Accredited Certification (ACAC) through its CMC Certification Board and accredited by CESB. It is unrelated to other credentials that share the acronym.
The exam has 120 multiple-choice questions, each with at least four answer options, delivered on a computer over three hours, closed book. The passing score is 75%, set using a Modified Angoff process. ACAC does not publish the scored versus unscored split.
The initial two-year term totals $500: a $100 examination fee plus a $400 certification fee, which includes $100 nonrefundable processing. A retake costs $100, and renewal costs $400. No separate member or non-member schedule is published.
No. ACAC publishes no mandatory preparation course and no minimum training-hour requirement, though it maintains a provider directory. What you must document is microbial sampling experience, four project sheets, transcripts where applicable and experience verification.
Not on its own. The 2025 figure reflects 16 passes from 17 attempts, includes retakes and state-licensing-only candidates, and is not first-attempt data. Candidates also pass an experience-review gate before testing, which shapes who sits for the exam.