- How ACAC Structures the CIE Exam
- Domain 1: IAQ Contaminants and Potential Health Effects
- Domain 2: Principles of Building Science & the Built Environment
- Domain 3: HVAC
- Domain 4: Equipment Selection, Calibration and Operation
- Domain 5: Guidelines, Regulations and Standards
- Domain 6: Remediation
- Domain 7: Respiratory Protection
- Reference-to-Domain Crosswalk
- Sequencing the Domains in Your Prep
- Format, Fees and Exam-Day Mechanics
- Frequently Asked Questions
- ACAC's official chart lists seven CIE domains, including a standalone Respiratory Protection domain.
- ACAC publishes no percentage weights, so no domain can be called "most heavily tested."
- The exam is 100 multiple-choice questions in three hours, closed book, with a 75% passing score.
- The handbook's six-heading body-of-knowledge list omits Respiratory Protection; the seven-domain chart controls.
How ACAC Structures the CIE Exam
The Council-certified Indoor Environmentalist (CIE) credential is issued by the American Council for Accredited Certification (ACAC) through its CIE Certification Board, and the program is accredited by the Council for Engineering and Scientific Specialty Boards (CESB). The authoritative statement of what the exam covers is ACAC's official exam-domain and subdomain chart for the CIEC and CIE examinations, approved February 7, 2024. That chart expressly covers CIE and lists seven formal domains. No separately labeled 2026 exam version has been verified, so treat the February 2024 chart as the current published blueprint and check ACAC for updates before you test.
Two cautions shape how you should read any "domain guide," including this one:
- No published weights. ACAC does not publish percentage weights or per-domain question counts. The handbook mentions roughly twenty questions per domain, but that wording conflicts with seven domains and 100 total questions, so no counts can be inferred from it. Be skeptical of any prep site that assigns a "percent of the exam" to a domain; those numbers describe the vendor's own practice material, not the exam.
- Handbook versus chart. The CIE Candidate Handbook's shorter body-of-knowledge list has six headings and omits Respiratory Protection as a standalone item. The linked seven-domain chart is the more specific and controlling source, so study Respiratory Protection as its own domain.
Domain 1: IAQ Contaminants and Potential Health Effects
This domain asks you to connect what is in the air and on surfaces of a building with what it can do to occupants. Expect scenario-style questions in which a complaint pattern, a building condition and a candidate contaminant must be reasoned together rather than recalled in isolation.
What to master in Domain 1
Think in three layers: source, pathway, and receptor.
- Biological contaminants: mold and other microbial growth, the conditions that support it, and how occupants may respond. The AIHA text on recognition, evaluation and control of indoor mold is your anchor reference here.
- Chemical contaminants: combustion byproducts, volatile organic compounds and other gases and vapors that originate from building materials, occupant activities or outdoor intrusion.
- Particulates and fibers: how particles are generated, transported and deposited, and why size and composition matter to evaluation.
- Health-effect reasoning: distinguishing symptoms that track occupancy and building location from those that do not, and knowing the limits of what an indoor environmental investigator can conclude.
A common trap is treating a sample result as a verdict. The exam rewards candidates who understand that health-effect statements depend on exposure, susceptibility and context, and who stay within the scope of what an investigator can support.
Domain 2: Principles of Building Science & the Built Environment
Building science is the "why" behind most indoor air quality problems. This domain tests whether you understand how heat, air and moisture move through a building enclosure and how those flows create or prevent contamination conditions.
What to master in Domain 2
- Moisture mechanics: liquid water, capillary movement, vapor diffusion and condensation, and how each leaves different evidence in a building.
- Air movement and pressure: stack effect, wind and mechanical pressure differences, and how they pull outdoor air, soil gas or contaminants through leaks.
- Enclosure and construction: how assemblies, materials and details perform when wet and how design choices affect drying potential.
- Source tracing: using building knowledge to move from a symptom to a root cause rather than treating only the visible damage.
The EPA building air quality guide for owners and facility managers is a practical companion for this domain because it frames IAQ problems as the interaction of sources, ventilation, occupants and the building itself.
Domain 3: HVAC
HVAC is where ventilation, filtration and contaminant distribution meet. Candidates searching for a "CIE HVAC study guide" should note that HVAC is one of seven domains, not the whole exam, but it feeds directly into several others.
What to master in Domain 3
- System types and components: how air is conditioned, distributed and returned, and where each component can contribute to or relieve a problem.
- Ventilation and outdoor air: why outdoor air delivery matters, how it is controlled, and what happens when it is reduced or misdirected.
- Filtration and moisture control: what filters can and cannot do, and how coil, drain pan and humidity-control issues create microbial amplification sites.
- Diagnosing system-related complaints: recognizing when pressure relationships, short-circuiting or poor distribution explain uneven conditions.
Managing Indoor Air Quality (fifth edition, 2011), a listed CIE reference, is the natural place to ground your HVAC reasoning. Note that the CIE reference list specifies the fifth edition; do not substitute the edition associated with the sister CIEC program.
Domain 4: Equipment Selection, Calibration and Operation
This domain is about measurement integrity. It is easy to underestimate because it sounds like a gear list, but the questions tend to test judgment: choosing the right instrument for the question being asked, operating it correctly and knowing when the data cannot be trusted.
What to master in Domain 4
- Selecting instruments to fit the question: matching a moisture, airflow, pressure, particle, gas or sampling tool to the hypothesis you are testing.
- Calibration and quality control: why calibration status, checks before and after use, and documentation affect whether results are defensible.
- Operation and limitations: proper technique, common sources of error and the conditions under which a reading is unreliable.
- Sampling logic: collecting representative samples, including appropriate controls, so that results can actually be interpreted.
If you came to CIE from field work, resist answering from habit. The exam wants the technically correct choice, not necessarily the one your employer's toolkit favors.
Domain 5: Guidelines, Regulations and Standards
This domain tests whether you know what guidance exists, what is binding and what is advisory. Indoor air quality has few enforceable numeric limits, so distinguishing a regulation from a guideline from a consensus standard is a recurring skill.
What to master in Domain 5
- Binding versus advisory: knowing which sources carry legal force and which inform professional practice.
- Occupational frameworks: how workplace exposure and worker-protection requirements relate to the work an investigator or remediator performs.
- Industry guidance: where mold, ventilation and building-air-quality guidance comes from and how it is used when no hard limit exists.
- Scope and licensing awareness: understanding that state licensing and ACAC certification are separate processes. A licensing-only exam pass does not authorize use of the CIE designation.
Domain 6: Remediation
Remediation questions test whether you can move from assessment findings to a sound, safe plan, and whether you understand how success is judged. The emphasis is on principles and sequence rather than brand-specific procedures.
What to master in Domain 6
- Fix the cause first: why removing contaminated material without correcting the moisture or source problem invites recurrence.
- Containment and control: how work areas are isolated and how pressure and air handling limit spread during the work.
- Removal and cleaning approaches: matching method to material and contamination type.
- Verification: how clearance and post-work evaluation are approached and the limits of what they can demonstrate.
- Worker and occupant protection: the link to Domain 7, since remediation scope drives protection requirements.
The AIHA mold text and the EPA building guide both inform this domain. Read them with a project-sequence mindset: assessment, plan, containment, work, verification.
Domain 7: Respiratory Protection
Respiratory Protection is a dedicated domain in the official chart, which is why relying on the handbook's six-heading list is risky. Two listed references speak directly to it: the NIOSH respirator selection logic document (2004) and the OSHA small entity compliance guide for the Respiratory Protection Standard (2011).
What to master in Domain 7
- Selection logic: working from the hazard and exposure situation to an appropriate class of respirator, using a structured decision process.
- Program elements: the components of a compliant respiratory protection program, including medical evaluation, fit testing, training and maintenance.
- Limitations: what different respirator types do not protect against, and the conditions that make a choice inappropriate.
- Connection to the work: tying protection decisions to the tasks an investigator or remediation worker will actually perform.
Because this domain is document-driven, it rewards careful reading of the two short government references more than broad background knowledge. Our guide to CIE exam difficulty discusses why domains like this are easy to neglect and costly to miss.
Reference-to-Domain Crosswalk
ACAC's CIE section lists five references. The study guide recommends reading the listed texts in full before revisiting selected sections, and it notes that its page recommendations are not exhaustive exam coverage. The crosswalk below is this guide's own study aid based on each reference's subject matter, not an official ACAC mapping.
| Listed reference | Most relevant domains (study aid) |
|---|---|
| AIHA, Recognition, Evaluation & Control of Indoor Mold, 2nd ed. (2020) | 1 (Contaminants), 4 (Equipment/sampling), 6 (Remediation) |
| EPA, Building Air Quality: A Guide for Building Owners and Facility Managers (1991) | 2 (Building science), 3 (HVAC), 5 (Guidelines) |
| Managing Indoor Air Quality, 5th ed. (2011) | 1, 2, 3, 4 (broad IAQ practice) |
| NIOSH, Respirator Selection Logic (2004) | 7 (Respiratory Protection), 5 (Guidelines) |
| OSHA, Small Entity Compliance Guide for the Respiratory Protection Standard (2011) | 7 (Respiratory Protection), 5 (Guidelines), 6 (Remediation worker protection) |
Publication dates here are bibliographic details, not exam-version dates. Notice that several references serve more than one domain, which is a reason to read them whole instead of hunting for a single chapter per domain.
Sequencing the Domains in Your Prep
Since ACAC publishes no weights, schedule by dependency rather than by guesswork. Contaminants and building science explain the problems; HVAC and equipment explain how you investigate; regulations, remediation and respiratory protection explain what you do about it. This sample order puts prerequisite concepts first.
Domains 1 and 2
- Read the AIHA mold text and the EPA guide in full once.
- Build source-pathway-receptor and moisture-flow reasoning before touching instruments.
Domains 3 and 4
- Work through Managing Indoor Air Quality (5th ed.) for HVAC and measurement logic.
- Practice choosing an instrument for a stated question and judging whether the data are reliable.
Domains 5, 6 and 7
- Sort sources into binding versus advisory, then rehearse a remediation sequence end to end.
- Read the NIOSH and OSHA respirator documents closely and test yourself on selection and program elements.
Mixed review
- Take timed mixed-domain sets on the CIE practice test site and log misses by domain.
- Revisit your weakest domain and the references that serve it.
Key Takeaway
Tag every missed practice question with its domain number. After a few sessions your misses will cluster, and that cluster, not a guess about hidden weights, tells you where to spend the next week. For a one-page review once you have built your notes, see the CIE cheat sheet.
Format, Fees and Exam-Day Mechanics
Knowing the container for the seven domains helps you pace and plan.
| Item | Published detail |
|---|---|
| Questions | 100 multiple-choice, at least four answer options each |
| Time | Three hours, computer-delivered, closed book |
| Passing score | 75%, set by the CIE Certification Board using the Modified Angoff method |
| Delivery | Testing center or online video proctoring scheduled through ACAC; Kryterion, Inc. delivers the exam |
| Initial fees | $100 examination plus $400 certification, $500 total for the initial two-year term |
| Retake / renewal | $100 retake; $400 renewal |
The scored versus unscored question split is not published, and the handbook describes a common question set with randomized question and answer order, electronic grading and immediate scores. Candidates should bring two government-issued IDs, including one photo ID, to a testing center. Online candidates need a computer, an approved webcam, a private location and at least 2 Mbps upload and download; phones and tablets are excluded. ACAC's examinations page and the handbook give different early-arrival times (15 versus 30 minutes), so arrive at the longer interval. Passing the exam alone does not finish certification; the board must also approve your application.
For the full picture of costs, see CIE Certification Cost 2026. For eligibility and the four project sheets that accompany the application, read CIE Requirements 2026. For performance context, ACAC's 2025 report shows 22 passes from 33 CIE examinations, printed as 66%, but that figure includes retakes and licensing-only examinations; our CIE pass rate analysis explains how to read it. For the numeric threshold, see CIE Passing Score 2026.
Frequently Asked Questions
ACAC's official exam-domain chart, approved February 7, 2024, lists seven: IAQ Contaminants and Potential Health Effects; Principles of Building Science & the Built Environment; HVAC; Equipment Selection, Calibration and Operation; Guidelines, Regulations and Standards; Remediation; and Respiratory Protection.
That cannot be determined. ACAC does not publish percentage weights or per-domain question counts, so any claimed weighting comes from a third party's own materials rather than from the exam blueprint. Prepare all seven domains.
The CIE Candidate Handbook's body-of-knowledge list has six headings and omits Respiratory Protection as a standalone item. The linked seven-domain chart is the more specific source, so treat Respiratory Protection as its own domain.
They are the official starting point, and the study guide recommends reading them in full before revisiting selected sections. It also states that its page recommendations are not exhaustive exam coverage, so pair the reading with practice questions. Review the study guide and the practice test to check retention.
No. They are separate ACAC credentials that share an official domain chart, but eligibility rules and the listed edition of Managing Indoor Air Quality differ. Do not carry CIEC requirements into your CIE planning; verify the CIE requirements directly.