- The Credential Defined
- Who Issues the Credential and Who Hires for It
- How the Examination Is Built
- The Seven Examination Domains
- Eligibility: Education Plus Documented Field Work
- From Application to Test Day
- Fees, Validity and Renewal
- Reading the Published Pass Ratio
- The Handbook Reading List
- Sequencing Your Study by Domain
- Frequently Asked Questions
- CIEC means Council-certified Indoor Environmental Consultant, issued by the American Council for Accredited Certification (ACAC).
- The exam is 120 multiple-choice questions in 3 hours, closed-book, with a 75% passing score.
- Eligibility pairs education with four to eight years of documented IAQ investigation work, plus four project sheets.
- First-term cost is $500 in the US/Canada; renewal is $400 plus 40 recertification credits every two years.
The Credential Defined
CIEC stands for Council-certified Indoor Environmental Consultant. It is a professional designation for people who investigate and diagnose indoor air quality (IAQ) problems in buildings: mold, chemical contaminants, ventilation failures, moisture intrusion and the health complaints that come with them. It is not an entry-level certificate you earn by sitting through a class. It is a peer-reviewed credential that requires documented field experience, a written examination and a unanimous vote of the certifying board.
Because the acronym is used elsewhere in the professional world, it is worth being precise: everything in this article refers only to the ACAC credential for indoor environmental consulting. If you are comparing wording variations, our short explainers on what CIEC stands for and what CIEC certification is cover the naming in more detail.
Who Issues the Credential and Who Hires for It
The issuing body is the American Council for Accredited Certification, usually shortened to ACAC. The council publishes a candidate handbook, a domain chart, a fee schedule and recertification procedures, all of which are referenced throughout this guide. ACAC administers the credential; it does not run a mandatory training program, and no specific course is required to qualify.
The people who pursue this designation typically work in or around:
- Independent indoor environmental and IAQ consulting firms
- Industrial hygiene and environmental health and safety practices
- Mold assessment and remediation oversight
- Building diagnostics, commissioning and facility management
- Insurance, legal and property-management work where an investigator's findings carry weight
The credential matters most where a consultant's written conclusions will be scrutinized by clients, attorneys, regulators or building occupants. For the employment side, see our overview of CIEC jobs, and for earnings context see the CIEC salary guide. We deliberately do not quote salary numbers here, because no verified figure belongs in an introductory article.
How the Examination Is Built
The CIEC examination is a closed-book, written test with a fixed structure:
| Feature | Detail |
|---|---|
| Number of questions | 120 |
| Question type | Multiple choice, with at least four answer choices per item |
| Time allowed | 3 hours |
| Reference materials | None; closed-book |
| Passing score | 75% |
| Standard-setting method | Modified Angoff |
| Delivery | Kryterion, at a testing center or by online video proctoring |
| Score reporting | Electronic, available immediately |
The 75% threshold was set with the modified Angoff method, in which subject-matter experts estimate how a minimally competent candidate would perform on each item. The practical meaning: the bar reflects a judgment about professional competence, not a curve against other test-takers. A closer look at the arithmetic is in our CIEC passing score guide.
Because the exam is closed-book, you cannot rely on looking up exposure limits, filter ratings or standard section numbers. Questions are scenario-flavored in the way consulting work is: you are expected to recognize what a set of building conditions or sampling results implies, then choose the defensible next step. For a realistic sense of the challenge, read how hard the CIEC exam is.
The Seven Examination Domains
ACAC's CIEC and CIE Examinations domain chart, approved February 7, 2024, lists seven domains. One important detail: the candidate handbook's abbreviated list shows only six headings and leaves out Respiratory Protection. The complete chart includes it, so plan to study all seven. ACAC does not publish percentage weights for these domains in the complete chart, so be skeptical of any source that claims to know exact weighting. Our complete guide to the seven CIEC content areas goes deeper into each one.
Domain 1: IAQ Contaminants and Potential Health Effects
The foundation of the exam. You need to connect contaminant sources to the symptoms and health outcomes they plausibly cause.
- Biological contaminants, especially mold and moisture-driven growth
- Chemical contaminants and volatile compounds in buildings
- Particulates, combustion by-products and other common IAQ agents
- How exposure, susceptibility and dose shape health effects
Domain 2: Principles of Building Science & the Built Environment
Why buildings fail the way they do. Moisture and air movement explain most IAQ complaints.
- Heat, air and moisture flow through building envelopes
- Pressure relationships and how they drive contaminant transport
- Condensation, water intrusion and drying behavior of materials
Domain 3: HVAC
Mechanical systems are both a cause and a cure for IAQ problems.
- Ventilation, outdoor air delivery and air distribution
- Filtration, humidity control and system maintenance issues
- How HVAC operation can spread or dilute contaminants
Domain 4: Equipment Selection, Calibration and Operation
Investigators are judged on their data. This domain tests whether you can choose and run instruments correctly.
- Matching instruments and sampling methods to the question being asked
- Calibration practices and why they protect data quality
- Operating limitations that can invalidate a reading
Domain 5: Guidelines, Regulations and Standards
Knowing which document applies, and what it does and does not require.
- Distinguishing enforceable regulations from voluntary guidance
- Recognizing the roles of agencies and professional organizations
- Applying published guidance to a described situation
Domain 6: Remediation
From findings to a defensible corrective plan.
- Containment, source removal and cleaning principles
- Worker and occupant protection during remediation work
- Verifying that remediation actually worked
Domain 7: Respiratory Protection
A distinct domain, and the one candidates most often overlook because the handbook's short list drops it.
- Selecting appropriate respirators for the hazard
- Program requirements surrounding respirator use
- Limitations of different respirator types
Key Takeaway
Do not treat Respiratory Protection as optional. It appears in the complete domain chart even though the handbook's six-heading summary omits it, and two of the handbook's recommended references are devoted to it.
Eligibility: Education Plus Documented Field Work
The CIEC is experience-gated, which is a major difference from credentials you can attempt straight after studying. ACAC offers three routes, each pairing education with documented IAQ investigation experience:
| Education | Documented IAQ investigation experience |
|---|---|
| Qualifying science-related four-year degree, or 30-credit equivalent | 4 years |
| Qualifying two-year degree, or 15-credit equivalent | 6 years |
| High-school diploma or GED | 8 years |
Your experience must span at least three of five areas: Lead/Asbestos, Microbial, IH/Chemicals/Toxicology, Building Sciences, and IAQ/HVAC. This breadth requirement filters out narrow specialists and shapes what the exam expects you to know.
You also submit four project sheets, applicable education transcripts and required email verifications. Certification requires unanimous board approval. One point trips people up: passing the examination for state licensing purposes alone does not confer the CIEC designation. The full qualification picture is laid out in our CIEC requirements guide.
From Application to Test Day
The process runs roughly in this order:
- Confirm eligibility. Match your degree and years of documented IAQ work against the three routes above.
- Document your projects. Prepare four project sheets that demonstrate real investigations across at least three of the five experience areas.
- Submit the official application. Include transcripts and arrange the required email verifications.
- Schedule the exam through the testing provider. Choose a Kryterion testing center or online video proctoring.
- Sit the exam. You will see your electronic score immediately.
- Await board review. Certification still depends on unanimous board approval.
Fees, Validity and Renewal
ACAC's published fee structure, in US dollars:
| Item | Amount |
|---|---|
| Examination fee | $100 |
| Certification fee | $400 |
| First two-year term total (US/Canada) | $500 |
| First two-year term total (outside US/Canada) | $525 |
| Retake | $100 |
The credential is valid for two years. Renewal costs $400 and requires 40 recertification credits: 10 credits for attesting to continued field activity, plus 30 hours of professional development. Keep your documentation, because renewals can be audited. For a fuller treatment, see the CIEC certification cost breakdown, and if you are weighing the investment, is the CIEC certification worth it frames the decision.
Reading the Published Pass Ratio
ACAC's 2025 Exam Pass Ratio reports 61%, with 28 passing out of 46 examinations. Read that carefully. The report includes retakes and state-licensing-only examinations, so it is not a first-attempt pass rate for CIEC candidates. The sample is also small, which means year-to-year swings are expected. Treat 61% as a rough indicator that a meaningful share of attempts do not pass, not as a prediction for your own result. More context is in our CIEC pass rate analysis.
The Handbook Reading List
The candidate handbook prescribes preparation references. These are the verified titles:
- AIHA, Recognition, Evaluation & Control of Indoor Mold, second edition (2020)
- EPA, Building Air Quality: A Guide for Building Owners and Facility Managers (1991)
- Managing Indoor Air Quality, fourth or fifth edition (2008/2011)
- NIOSH, Respirator Selection Logic (2004)
- OSHA, Small Entity Compliance Guide for the Respiratory Protection Standard (2011)
Notice how the list maps onto the domains. Mold and contaminants anchor the AIHA text, the EPA guide ties together building science and HVAC, and the NIOSH and OSHA documents cover respiratory protection. Since this is a closed-book exam, read these to understand reasoning, not to memorize page numbers. Our CIEC training overview discusses how these sources fit alongside optional coursework.
Sequencing Your Study by Domain
Because no course is mandatory, how you sequence your reading matters. One sensible order follows the logic of an investigation: start with what is wrong, then why the building allows it, then how it is measured, and finally how it is fixed.
Contaminants and building science
- Domain 1 and Domain 2 together, using the AIHA mold text and the EPA building guide
- Reason: moisture and airflow explain most contaminant problems
HVAC and instruments
- Domain 3 and Domain 4, pairing system behavior with the measurements used to diagnose it
Standards, remediation and respirators
- Domain 5, Domain 6 and Domain 7, finishing with the NIOSH and OSHA respirator documents
If you have strong field experience in one area, shorten that block and give the saved time to your weakest of the five experience areas. Our CIEC study guide expands this approach, and the CIEC cheat sheet is useful for last-pass review. To test yourself under exam-style conditions, try the practice questions on the CIEC Exam Prep practice test site, and use the full-length practice exams to build stamina for a three-hour sitting.
Frequently Asked Questions
CIEC stands for Council-certified Indoor Environmental Consultant, a credential issued by the American Council for Accredited Certification (ACAC) for professionals who investigate indoor air quality problems.
The exam has 120 multiple-choice questions, each with at least four answer choices, and you have 3 hours. It is closed-book, and the passing score is 75%.
Not necessarily. ACAC accepts a qualifying four-year degree plus four years of documented IAQ investigations, a two-year degree plus six years, or a high-school diploma or GED plus eight years. Experience must cover at least three of five defined areas.
For the first two-year term, the examination fee of $100 plus the certification fee of $400 comes to $500 in the US and Canada, or $525 elsewhere. A retake costs $100, and renewal is $400 plus 40 recertification credits.
No. Passing the examination for state licensing alone does not confer the CIEC designation. You must meet ACAC's eligibility and application requirements, including board approval, to be certified.
No. ACAC's 2025 figure of 61% (28 of 46 examinations) includes retakes and state-licensing-only examinations, so it should not be read as a first-attempt rate for CIEC candidates.