- What the Five CIES Domains Actually Are (and Are Not)
- Exam Format That Frames Every Domain
- Domain 1: Asbestos
- Domain 2: Lead
- Domain 3: Hazardous Materials
- Domain 4: Microbial Contaminants and Allergens
- Domain 5: Chemicals
- The Four Threads Running Through Every Domain
- Reference Map: What to Read for Each Domain
- Sequencing the Domains Around Your Field Experience
- Domains, Project Sheets, and Eligibility
- Frequently Asked Questions
- CIES here means Council-certified Indoor Environmental Supervisor, issued by ACAC's CIES Certification Board.
- The five domains are asbestos, lead, hazardous materials, microbial contaminants and allergens, and chemicals.
- No official domain weights are published, so treat the five areas as equally worth mastering.
- The exam has 120 multiple-choice questions, three hours, closed book, and a 75% passing score.
What the Five CIES Domains Actually Are (and Are Not)
The Council-certified Indoor Environmental Supervisor credential is issued by the American Council for Accredited Certification (ACAC) through its CIES Certification Board, and the program is accredited by the Council for Engineering and Scientific Specialty Boards (CESB). If you are new to the credential itself, start with What Is CIES Certification? before diving into content areas.
ACAC's candidate handbook publishes five competency headings. Each begins with the same phrase, "understand and execute successful remediation," followed by a different contaminant class in the indoor environment. This article treats those five headings as the study framework for the exam. That framing comes with some honest caveats:
- The competencies are unweighted. No public blueprint assigns percentages to any domain, and no one can credibly tell you which area is "worth the most" questions.
- Five is the heading count, not a declared official domain count. The handbook says the board prescribes an exam blueprint, but that chart is not reproduced publicly.
- The public study guide is not exhaustive. ACAC states that its selected pages are examples and advises comprehensive study of the listed references.
Exam Format That Frames Every Domain
Before the domain-by-domain breakdown, anchor yourself in how the content is tested. The exam is delivered through Kryterion, Inc., and the published parameters are:
| Element | Published detail |
|---|---|
| Questions | 120 multiple-choice, each with at least four answer options |
| Time | Three hours, computer-delivered, closed book |
| Passing score | 75%, set using Modified Angoff |
| Scored vs. unscored items | Split not published |
| Practical component | No separate practical assessment described |
| Delivery | Proctored testing center or online with video proctoring |
| Item presentation | Fixed question set with randomized item and answer order (per the handbook) |
| Results | Available electronically immediately, confirmed by email |
Three hours for 120 questions averages out to 90 seconds per item, which is generous for recall questions but tight for multi-step scenarios. For a deeper look at the cut score, see CIES Passing Score 2026: Exactly What You Need to Pass, and for how the format affects difficulty, read How Hard Is the CIES Exam? Complete Difficulty Guide 2026.
Because every published competency addresses engineering controls, cleaning or removal methods, worker safety, and applicable regulations, expect questions that ask you to choose the right action in a supervised remediation situation rather than simply define a term. A supervisor-level exam rewards judgment: what do you do first, what control is appropriate, which rule governs.
Domain 1: Asbestos
Understand and execute successful remediation of asbestos in the indoor environment
This is the first of the five published competencies and one where the regulatory backbone is unusually dense. Candidates should be able to connect a work scenario to the correct governing standard and the correct control strategy.
- Regulatory frameworks named in the handbook's reference list: 40 CFR 763 (the EPA asbestos rule), 40 CFR 61 Subpart M (the asbestos NESHAP), and 29 CFR 1926.1101 (the OSHA construction asbestos standard)
- Engineering controls such as containment, negative air, and wet methods, and why each is chosen
- Removal and cleaning methods, including how clean-up verification fits the job
- Worker protection: respirator selection, decontamination, and exposure-related responsibilities of a supervisor
The trap in this domain is confusing which standard applies to which activity. The EPA rules, the NESHAP, and the OSHA construction standard overlap in subject matter but address different obligations. Build a one-page comparison of what each regulation governs and who it binds. That single exercise pays off across many question types.
Domain 2: Lead
Understand and execute successful remediation of lead in the indoor environment
Lead questions tend to blend regulatory knowledge with practical work-practice decisions, especially in older building stock.
- Regulatory references: 40 CFR 745 (EPA lead rules) and 29 CFR 1926.62 (the OSHA construction lead standard)
- Work practices that control dust and contamination during disturbance of lead-containing materials
- Cleaning and clearance concepts, and what separates cleaning from true removal
- Worker safety: exposure assessment, protective equipment, hygiene facilities, and medical surveillance concepts
As with asbestos, the discipline here is separating the EPA's concerns (largely protecting building occupants and renovation settings) from OSHA's concerns (protecting workers). When a scenario describes a crew, a work area, and an exposure, ask yourself which framework the question is really testing before you read the answer options.
Domain 3: Hazardous Materials
Understand and execute successful remediation of hazardous materials in the indoor environment
This is the broadest and least predictable competency, which makes it the one candidates most often under-prepare.
- 29 CFR 1910.120 (HAZWOPER) appears on the handbook's listed references and anchors the worker-safety side of hazardous materials response
- Emergency-response versus planned-remediation thinking: who is authorized to do what
- Mercury material, covered in the handbook's reference caveats (see below)
- Clandestine methamphetamine laboratory cleanup, supported by the EPA Voluntary Guidelines for Methamphetamine Laboratory Cleanup in the reference list
- Respiratory protection logic, supported by the NIOSH Respirator Selection Logic (2004)
Candidates from asbestos or mold backgrounds often discover that this domain asks them to think like a generalist. Practice reading a scenario and identifying the contaminant class first, then the control, then the rule.
Domain 4: Microbial Contaminants and Allergens
Understand and execute successful remediation of microbial contaminants and allergens in the indoor environment
If your experience is mold remediation, this is probably your home turf. It is also where over-confidence is most dangerous, because the exam is not mold-only.
- Primary listed reference: the New York City Department of Health and Mental Hygiene, Guidelines on Assessment and Remediation of Fungi in Indoor Environments (2008)
- Source identification and moisture control as the foundation of any microbial remediation
- Containment and engineering controls scaled to the size and condition of the affected area
- Cleaning and removal methods for porous versus non-porous materials
- Worker safety and the role of personal protective equipment in microbial work
Note the word "allergens" in the competency heading. Treat it as an instruction to broaden beyond visible mold toward the wider category of biological contaminants that affect indoor air quality. For candidates comparing credentials, ACAC's mold-focused certification covers a narrower scope, and our guide to whether CIES certification is worth it discusses how that breadth factors into the decision.
Domain 5: Chemicals
Understand and execute successful remediation of chemicals in the indoor environment
The fifth competency maps to the experience area ACAC labels "IH/Chemicals/Toxicology," meaning industrial hygiene fundamentals alongside chemical remediation.
- Basic toxicology concepts: routes of exposure, dose and response, acute versus chronic effects
- Industrial hygiene thinking: recognition, evaluation, and control hierarchy
- Engineering controls such as ventilation and source isolation versus reliance on respiratory protection
- Respirator selection logic and its limits
- Applicable regulatory and safety frameworks tied to chemical exposure in the workplace
The control hierarchy is the single most reusable idea in this domain. Questions often present several plausible responses, and the best answer is typically the one higher on the hierarchy (eliminate or isolate the hazard) rather than the one that depends on worker behavior or personal protective equipment alone.
The Four Threads Running Through Every Domain
ACAC's handbook states that each published competency addresses the same four themes. Use them as a matrix for your notes: five domains across, four threads down.
| Thread | What to be able to explain in each domain |
|---|---|
| Engineering controls | Which containment, ventilation, or isolation measure fits the contaminant and why |
| Cleaning / removal methods | Accepted techniques, sequencing, and how success is confirmed |
| Worker safety | PPE, respiratory protection, decontamination, training, and supervisory duties |
| Applicable regulations | Which rule governs the activity and what it requires |
Filling in all twenty cells of that grid is a more reliable study outcome than memorizing isolated facts. If a cell is blank, that is where your next study session belongs. Our CIES Cheat Sheet 2026 is a useful companion for compressing that grid into a one-page review.
Reference Map: What to Read for Each Domain
The handbook's listed preparation references are the closest thing to an official reading list. Mapping them to domains helps you avoid studying the wrong document for the wrong problem:
- Asbestos: 40 CFR 763; 40 CFR 61 Subpart M; 29 CFR 1926.1101
- Lead: 40 CFR 745; 29 CFR 1926.62
- Hazardous materials: 29 CFR 1910.120; EPA Voluntary Guidelines for Methamphetamine Laboratory Cleanup; mercury references (EPA Region 5 and the National Elemental Mercury Response Guidebook)
- Microbial and allergens: NYC DOHMH Guidelines on Assessment and Remediation of Fungi in Indoor Environments (2008)
- Chemicals / worker protection across domains: NIOSH Respirator Selection Logic (2004)
- Professional conduct: the ACAC Code of Conduct
A note of caution: the publication dates of these references are not exam-version dates. The public handbook page is undated, and no separately identified 2026 exam version was verified. Always confirm against the current ACAC handbook before you build a study plan, and see CIES Study Guide 2026: How to Pass on Your First Attempt for the full preparation workflow.
Sequencing the Domains Around Your Field Experience
Because you are likely qualifying on at least three of the five experience areas (Asbestos; Lead; Hazardous Materials; Microbial/Allergens; IH/Chemicals/Toxicology), your study order should front-load the domains where you have the least hands-on exposure. Experience will carry you through your strong areas; the weak ones need structured reading. A sample rhythm:
Your two weakest domains
- Read the governing regulations end to end, not summaries
- Fill the four-thread grid for each
Hazardous materials and chemicals
- Work through HAZWOPER concepts, mercury sources, and the control hierarchy
- Drill respirator selection logic
Your strongest domains plus mixed practice
- Refresh with reference-explained questions rather than rereading
- Take timed sets at about 90 seconds per question
Timed practice matters because of the three-hour window. You can run realistic drills with the CIES practice tests and check your readiness against the full practice question bank.
Domains, Project Sheets, and Eligibility
The five domains connect directly to the application. ACAC requires experience covering at least three of the five areas, and applicants submit four project sheets. According to ACAC's FAQ, each sheet describes the problem, the applicant's own responsibilities and actions, and the outcome. Writing those sheets is itself domain review: you are articulating the same engineering-control, removal, safety, and regulatory reasoning the exam tests.
Prerequisite pathways, as published, are:
- A related four-year degree or 30 qualifying college credits, plus four years of documented indoor environmental remediation
- A related two-year degree or 15 qualifying credits, plus six years
- A high school diploma or GED, plus eight years
For the complete eligibility picture, read CIES Requirements 2026: Eligibility, Prerequisites & How to Qualify. On costs, ACAC lists a $100 examination fee plus a $400 certification fee (including a $100 nonrefundable processing fee), totaling $500 for the initial two-year term, with a $100 retake and $400 renewal; the breakdown is covered in CIES Certification Cost 2026. One thing to keep distinct: taking the exam solely for state licensing does not itself confer CIES certification, and state licensing eligibility is separate from ACAC certification eligibility.
Frequently Asked Questions
No public weights were verified. ACAC's handbook publishes five unweighted competency headings and says the board prescribes an exam blueprint, but no domain chart or percentages are reproduced. Prepare for all five areas rather than assuming one dominates.
No. Microbial contaminants and allergens is one of five competencies. Asbestos, lead, hazardous materials, and chemicals each have their own published heading, so a mold-only background leaves substantial gaps.
It depends on your experience. Hazardous materials is the broadest and least predictable, while others find the regulatory density of asbestos and lead demanding. Our difficulty guide explains how to assess your own gaps.
The exam is closed book. Calculator permission was not verified, so confirm directly with ACAC or Kryterion before test day rather than assuming one is allowed.
No reliable current figure was verified, and the published historical reports conflict on very small candidate counts. A dash in an ACAC report is not a 0% pass rate. See CIES Pass Rate 2026: What the Data Shows for the full explanation.