- What a CIEC Actually Is
- Who Issues the Credential
- What a CIEC Does on the Job
- Who Qualifies to Sit for It
- How the Exam Is Built
- The Seven Exam Domains
- The Handbook's Reading List
- Costs, Validity and Renewal
- What the Published Pass Ratio Does and Does Not Tell You
- Sequencing Your Preparation by Domain
- Frequently Asked Questions
- CIEC means Council-certified Indoor Environmental Consultant, a credential 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 requires documented IAQ investigation experience: four, six or eight years depending on your education.
- The first two-year term costs $500 in the US/Canada; renewal is $400 plus 40 recertification credits.
What a CIEC Actually Is
A CIEC is a Council-certified Indoor Environmental Consultant: a professional who has met the American Council for Accredited Certification's requirements for investigating and addressing indoor air quality (IAQ) problems in buildings. The designation is not a course completion certificate, and it is not granted simply for passing a test. It combines documented field experience, a proctored written examination, and a board review of your application materials.
If you have seen the acronym elsewhere, be careful: several unrelated credentials abbreviate to similar letters. This article covers only the ACAC credential. For a quick orientation on the wording itself, see our short explainers on what CIEC stands for and CIEC meaning, or the broader overview of CIEC certification.
Who Issues the Credential
The certifying body is the American Council for Accredited Certification (ACAC). ACAC publishes a CIEC Candidate Handbook, an examination domain chart (approved February 7, 2024), a fee schedule, recertification procedures, and the application forms. Those documents are the authoritative source for everything about the credential, and when they disagree with one another, which happens in a couple of places noted below, the practical move is to confirm with ACAC before you submit anything.
Exams are delivered through the testing provider Kryterion, either at a computer testing center or by online video proctoring. Electronic scores are available immediately after you finish. If you test at a center, you need two government-issued IDs, one of which must be a photo ID.
What a CIEC Does on the Job
The exam domains describe the actual work. An indoor environmental consultant is the person called when occupants report odors, symptoms, moisture damage, visible growth, or complaints that a building "makes people sick." The work typically involves:
- Interviewing occupants and reviewing building history to frame a hypothesis
- Inspecting the building envelope, mechanical systems and moisture pathways
- Selecting, calibrating and operating sampling and measurement equipment
- Interpreting results against applicable guidelines, regulations and standards
- Specifying remediation and verifying that it worked
- Advising on respiratory protection for workers and occupants during the process
Employers and clients tend to include environmental and industrial hygiene consulting firms, remediation contractors who want an independent assessor on staff, building owners and facility management groups, and public-sector or institutional facility teams. The experience requirement for the credential spans lead and asbestos work, microbial work, industrial hygiene and toxicology, building science, and HVAC, so people arrive from a wide mix of backgrounds. For more on career outcomes, see our pages on CIEC jobs and CIEC salary, and on whether the effort pays off in Is the CIEC Certification Worth It?
Who Qualifies to Sit for It
ACAC ties eligibility to a combination of education and years of documented IAQ investigations. There are three pathways:
| Education | Required IAQ Investigation Experience |
|---|---|
| Qualifying science-related four-year degree (or 30-credit equivalent) | Four years |
| Qualifying two-year degree (or 15-credit equivalent) | Six years |
| High-school diploma or GED | Eight years |
Regardless of pathway, your experience must span at least three of five areas: Lead/Asbestos, Microbial, IH/Chemicals/Toxicology, Building Sciences, and IAQ/HVAC. The application requires four project sheets, applicable education transcripts, and required email verifications. Certification also requires unanimous board approval, which is why the application packet deserves as much care as exam preparation.
The details of each pathway are covered in CIEC Requirements: Eligibility, Prerequisites and How to Qualify. No training course is mandatory, so there is no required class to buy before you apply, a point we expand on in our CIEC training overview.
The deadline discrepancy to watch
ACAC's current application instructions allow six months to complete the process, including taking the examination. The handbook, however, states 90 days. Because the two documents conflict, confirm the operative deadline with ACAC when you apply rather than assuming either number. Scheduling considerations are discussed further in CIEC Exam Dates: Testing Windows, Deadlines and Scheduling.
How the Exam Is Built
The CIEC examination is a closed-book written test with these specifications:
- 120 multiple-choice questions, each with at least four answer choices
- 3 hours of testing time, which works out to roughly 90 seconds per question
- 75% passing score, set using the modified Angoff method
- Computer delivery at a testing center or by online video proctoring
The modified Angoff method means a panel of subject-matter experts judges how a minimally competent candidate would perform on each question, and the cut score is derived from those judgments. In practical terms, 75% is a fixed target for a given form rather than a curve against other test-takers. Read more in CIEC Passing Score: Exactly What You Need to Pass.
Because it is closed-book, you cannot rely on looking up an exposure guideline, a filter rating, or a ventilation relationship. You need working recall plus the judgment to apply it. Questions are scenario-flavored in the sense that the domains describe investigative work, so expect to reason about what a practitioner would do, not just define terms. For a candid take on difficulty, see How Hard Is the CIEC Exam?
The Seven Exam Domains
ACAC's CIEC and CIE Examinations chart lists seven domains. One caution: the handbook's abbreviated list shows six headings and omits Respiratory Protection, and its approximate per-topic question counts do not reconcile with the seven-topic statement and the 120-question total. The complete chart is the reliable source for headings. ACAC does not publish percentage weights for these domains, so do not trust any site that quotes exact weights. Our complete guide to all seven content areas goes deeper on each one.
Domain 1: IAQ Contaminants and Potential Health Effects
The substance of what you might find and why it matters to occupants.
- Biological contaminants such as mold and bacteria, and the conditions that support them
- Chemical contaminants and combustion byproducts
- Particulates and other airborne pollutants
- Links between exposures and health complaints, and the limits of those links
Domain 2: Principles of Building Science & the Built Environment
How buildings handle moisture, heat and air, and how failures create IAQ problems.
- Moisture sources, transport and accumulation in assemblies
- Pressure relationships and air leakage across the envelope
- How construction and occupancy patterns create contaminant pathways
Domain 3: HVAC
The mechanical systems that distribute, condition and dilute indoor air.
- Ventilation and outdoor air delivery
- Filtration and air distribution
- How system design, operation and maintenance contribute to complaints
Domain 4: Equipment Selection, Calibration and Operation
Choosing the right tool and knowing whether to trust its reading.
- Matching instruments and sampling methods to the question being asked
- Calibration and quality control practices
- Correct operation and the sources of measurement error
Domain 5: Guidelines, Regulations and Standards
The framework that gives measurements meaning.
- Which documents are enforceable regulations and which are voluntary guidance
- How to use published guidance to frame findings and recommendations
Domain 6: Remediation
Fixing the problem and proving it stayed fixed.
- Source control, containment and cleaning approaches
- Protecting occupants and workers during remediation
- Post-remediation verification
Domain 7: Respiratory Protection
Selecting and using respirators within a compliant program.
- Respirator selection logic and matching protection to hazard
- Program elements such as fit and use requirements
The Handbook's Reading List
The CIEC Candidate Handbook prescribes preparation references. They are a reading list, not a mandatory course, and they map neatly onto the domains:
- AIHA, Recognition, Evaluation & Control of Indoor Mold (second edition, 2020), most relevant to contaminants, equipment and remediation
- EPA, Building Air Quality: A Guide for Building Owners and Facility Managers (1991), most relevant to building science, HVAC and investigation strategy
- Managing Indoor Air Quality (fourth or fifth edition, 2008/2011)
- NIOSH, Respirator Selection Logic (2004), directly tied to Domain 7
- OSHA, Small Entity Compliance Guide for the Respiratory Protection Standard (2011), also tied to Domain 7 and to regulatory content in Domain 5
Costs, Validity and Renewal
ACAC's fee schedule for the first two-year term works out as follows:
| Item | US/Canada (USD) |
|---|---|
| Examination fee | $100 |
| Certification fee | $400 |
| First two-year term total | $500 |
| Retake | $100 |
Outside the US and Canada, the first-term total is $525. Full breakdowns, including how these amounts fit into total career cost, are in CIEC Certification Cost: Complete Pricing Breakdown.
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 documentation in case ACAC audits your submission. Current procedures are posted on ACAC's recertification procedures page, so check it before each renewal cycle.
What the Published Pass Ratio Does and Does Not Tell You
ACAC's 2025 Exam Pass Ratio report lists 61%, based on 28 passing results out of 46 examinations. It is tempting to read that as "about six in ten first-time candidates pass," but the report includes retakes and state-licensing-only examinations, so it is not a first-attempt pass rate. The sample is also small, so the figure should be read as a rough indicator and not a forecast of your own odds. We unpack this further in CIEC Pass Rate: What the Data Shows.
The more useful signal is structural: because eligibility already screens for years of field experience, test-takers are working practitioners. The exam rewards breadth across all seven domains, and candidates who are deep in one area (say, mold) but thin in another (say, respiratory protection or HVAC) are the ones most exposed.
Sequencing Your Preparation by Domain
Generic study advice matters less here than matching your weak areas to the domain list. A sensible ordering starts with the domains where most candidates have gaps given the five-area experience mix: if your background is microbial or lead/asbestos, spend your early time on HVAC and building science; if you come from HVAC or building science, front-load contaminants and health effects.
Your weakest foundation domains
- Domain 2 (building science) and Domain 3 (HVAC) if you lack mechanical or envelope experience
- Domain 1 (contaminants and health effects) if you come from a mechanical background
Measurement and rules
- Domain 4: equipment selection, calibration and operation
- Domain 5: guidelines, regulations and standards, separating enforceable from advisory
Action and protection
- Domain 6: remediation and verification
- Domain 7: respiratory protection, using the NIOSH and OSHA references
Timed mixed practice
- Full-length sets under 3-hour conditions across all seven domains
- Review misses by domain to find the pattern
Key Takeaway
Do not skip Domain 7 because some handbook summaries omit it. ACAC's complete domain chart includes Respiratory Protection, so study it as a full domain. Then take timed practice questions on our CIEC practice test site to check your recall across all seven areas.
Because each additional hour should go where it moves your score most, use practice results to rebalance. If you want a structured way to find your gaps, start with a diagnostic on the main practice test page and plan from there.
Frequently Asked Questions
CIEC stands for Council-certified Indoor Environmental Consultant. It is a certification issued by the American Council for Accredited Certification (ACAC) to professionals who meet its education, experience and examination requirements in indoor air quality investigation.
The exam has 120 multiple-choice questions, each with at least four answer choices, delivered in 3 hours as a closed-book test. The passing score is 75%, set with the modified Angoff method.
No. ACAC does not mandate a training course. Eligibility depends on your education and documented IAQ investigation experience (four, six or eight years depending on your degree level), plus four project sheets, transcripts and email verifications.
For the first two-year term in the US or Canada, the total is $500: a $100 examination fee plus a $400 certification fee. Outside those countries it is $525, and a retake costs $100. Renewal is $400 with 40 recertification credits.
No. ACAC's 2025 figure (28 of 46 examinations) includes retakes and state-licensing-only exams, so it is not a first-attempt pass rate. It is also a small sample, so treat it as context, not a prediction.
In short, a CIEC is a field-experienced indoor environmental professional who has passed a rigorous, closed-book examination across seven domains and earned unanimous board approval. If that matches your career path, the next steps are confirming your eligibility pathway, building your project sheets, and preparing across every domain, including respiratory protection, before you schedule your exam.