- What the Six CEAI Domains Actually Are
- Exam Format Behind the Domains
- Domain 1: The Allergic Response in Humans
- Domain 2: Allergen Types in the Built Environment
- Domain 3: Principles of the Built Environment
- Domain 4: Investigation Principles, Procedures, and Equipment
- Domain 5: Evaluation and Remediation Strategies
- Domain 6: Guidelines, Regulations, and Standards
- The Seven Assigned Publications and the Domains
- Sequencing the Domains in Your Prep
- Eligibility, Fees, and Logistics That Frame Your Prep
- Frequently Asked Questions
- The Council-certified Environmental Allergen Investigator exam covers six domains, from the allergic response in humans to guidelines, regulations, and...
- The exam is 100 closed-book multiple-choice questions in 3 hours, with a 75% passing score.
- Domain percentage weights are not published in the reviewed ACAC sources, so study all six domains seriously.
- ACAC assigns seven publications and recommends reading complete texts rather than only highlighted review pages.
What the Six CEAI Domains Actually Are
The Council-certified Environmental Allergen Investigator (CEAI) credential is administered by the American Council for Accredited Certification (ACAC). Its six content areas come from the public examination headings in the ACAC Examination Study/Review Packet, a document shared across the CEAC, CEAI, and CEAT credentials. The domain names below reproduce the official CEAI headings. They are not an inferred curriculum or a borrowed consultant or technician syllabus.
This distinction matters. The shared packet covers several related certifications, but the CEAI exam is its own instrument. Details that belong to the consultant-level credential, such as its longer exam and heavier experience requirements, do not transfer to the investigator exam. If you are still orienting yourself, start with What Is CEAI Certification? and the CEAI requirements guide, then return here for the content map.
| Domain | Official Heading | Core Orientation |
|---|---|---|
| 1 | The allergic response in humans | Health science and exposure biology |
| 2 | Types of allergens and their presence in the built environment | Sources, reservoirs, and indoor occurrence |
| 3 | Principles of the Built Environment | Buildings, moisture, ventilation, and housing |
| 4 | Investigation principles, procedures, and equipment | Sampling, methods, and laboratory interface |
| 5 | Allergen evaluation and remediation strategies | Interpreting findings and reducing exposure |
| 6 | Guidelines, regulations, and standards | Reference frameworks and authoritative guidance |
Exam Format Behind the Domains
Knowing the delivery format helps you decide how deeply to study each domain and what kind of recall the questions demand.
- Length: 100 multiple-choice questions, each with at least four answer options.
- Time: 3 hours, which works out to roughly 1.8 minutes per question.
- Rules: Closed book, computer-delivered through the testing provider Kryterion, Inc.
- Delivery: Test center or secure online video-proctored.
- Passing score: 75%, set using the Modified Angoff Method, a standard-setting approach in which subject-matter experts judge how a minimally qualified candidate would perform on each item.
- Results: Scores are immediate, with email confirmation.
A 75% cut score on 100 questions means a margin of error of about 25 missed items. That sounds generous until you notice that six domains with no published weights leave little room to skip an area entirely. For a deeper look at scoring mechanics, see CEAI Passing Score 2026, and for how the difficulty feels in practice, read How Hard Is the CEAI Exam?
Domain 1: The Allergic Response in Humans
This domain establishes why an investigator is looking for allergens at all. Questions here tend to test whether you can connect biology to exposure, so you understand which findings matter to occupant health and which are incidental.
Domain 1: The allergic response in humans
Expect to understand how exposure leads to sensitization and symptoms, and how allergic disease relates to asthma and respiratory health in occupied buildings.
- How sensitization and allergic reactions develop, and why repeated exposure matters
- The difference between allergy, irritation, and infection in indoor settings
- Routes of exposure and why inhalation of airborne particles is central
- Asthma as a housing-related health concern
- Why individual susceptibility varies, limiting what a measurement alone can prove
Two assigned publications anchor this domain: the HHS booklet Airborne Allergens: Something in the Air (2003) and the HUD publication Healthy Homes Issues: Asthma (2012). Read both in full. They frame the health context in plain language, and the exam draws on that framing when it asks what an allergen is doing to a building's occupants.
Domain 2: Types of Allergens and Their Presence in the Built Environment
Domain 2 is the catalog of what you might find and where it lives. A competent investigator needs to know the major indoor allergen categories, their typical reservoirs, and the conditions that let them accumulate.
Domain 2: Types of allergens and their presence in the built environment
This is a source-and-reservoir domain: know the allergen, know where it hides, and know what building conditions favor it.
- Categories of indoor allergens, including biological particles of animal, arthropod, and fungal origin
- Typical reservoirs such as dust, upholstered furniture, bedding, carpet, and HVAC components
- How moisture and humidity influence allergen-producing organisms
- Seasonal and outdoor-to-indoor transport of airborne particles
- Why a single room can hold very different allergen loads than the room next door
The Levetin article on aeroallergen sampling (Current Allergy and Asthma Reports, 2004) and the CDC Healthy Housing Reference Manual, chapter 5 (2006), both support this domain. Pay attention to how the readings describe particle behavior, because later domains build on the idea that where an allergen settles determines how you sample for it.
Domain 3: Principles of the Built Environment
Many candidates underestimate this domain because it sounds like background. In practice, it is where an investigator's credibility is built. An allergen finding means little without an explanation of how the building produced and distributed it.
Domain 3: Principles of the Built Environment
Think of this as building science for allergen investigators: how structures, systems, and occupant behavior shape indoor exposure.
- Ventilation, air exchange, and air movement within and between spaces
- Moisture sources, humidity control, and the conditions that sustain biological growth
- Building materials, furnishings, and surfaces that retain or shed particles
- HVAC system roles in distributing or filtering airborne allergens
- Housing conditions and their relationship to occupant health
The background in architecture, engineering, industrial hygiene, or science that ACAC lists as qualifying education pays off here. If your experience is mostly in sampling and lab work rather than building systems, give this domain extra time. Pair it with the CDC Healthy Housing Reference Manual and the EPA Exposure Factors Handbook, chapter 19 (updated 2018), which helps connect building conditions and occupant behavior to exposure.
Domain 4: Investigation Principles, Procedures, and Equipment
This is the operational heart of the credential, and the domain most closely tied to the experience ACAC requires before you can even sit for the exam. Applicants must show experience designing and conducting investigations, so the exam expects practitioner-level fluency here.
Domain 4: Investigation principles, procedures, and equipment
Know how an investigation is planned, how samples are collected, and how results depend on method.
- Developing an investigation plan and a defensible sampling strategy
- Air sampling versus surface and dust sampling, and when each is appropriate
- Standardized dust collection, including vacuum sampling protocols for allergens
- Sampling equipment, its limitations, and how method choice affects interpretation
- Working with environmental laboratories, including what labs can and cannot report
- Documentation, chain of custody, and quality considerations
Three assigned publications map directly onto this domain: the HUD Vacuum Dust Sample Collection Protocol for Allergens (2008), the APHL primer Environmental Laboratories and Indoor Air Testing (2015), and Levetin's sampling article. Read the HUD protocol as a procedure, not a summary. Closed-book questions about sampling often reward candidates who can recall the logic of each step, including why it exists.
Domain 5: Allergen Evaluation and Remediation Strategies
Once the data exists, an investigator must decide what it means and what to do about it. Domain 5 tests judgment: interpreting findings in context and recommending proportionate responses.
Domain 5: Allergen evaluation and remediation strategies
This domain links measurement to action, so expect scenario-style reasoning about what to recommend.
- Interpreting sampling results alongside building conditions and occupant complaints
- Recognizing the limits of what a single sample can establish
- Source control, moisture correction, cleaning, and filtration strategies
- Prioritizing interventions based on likely exposure reduction
- Verifying that remediation worked, including post-remediation assessment
The HUD asthma publication and the CDC housing manual again carry weight, since both discuss practical intervention approaches in residential settings. A useful habit is to ask of every remediation method: what exposure pathway does this interrupt, and how would I confirm it worked? That question connects Domain 5 back to Domains 2 and 3.
Domain 6: Guidelines, Regulations, and Standards
The final domain covers the reference frameworks an investigator relies on. Allergen investigation is a field where authoritative guidance is often more important than hard numerical limits, so a candidate needs to understand what each source is and what weight it carries.
Domain 6: Guidelines, regulations, and standards
Know the major sources of guidance in this field and distinguish between enforceable requirements and advisory documents.
- Which publications and agencies supply the field's principal guidance
- The difference between regulation, standard, protocol, and recommendation
- How federal health and housing agencies frame allergen and asthma issues
- Why professional judgment must fill gaps where no numeric standard exists
The seven assigned publications themselves function as a map of this domain, because they come from federal public-health, housing, and environmental agencies and a public-health laboratory association. Treat each as both a content source and an example of how authoritative guidance is structured.
The Seven Assigned Publications and the Domains
ACAC recommends reading the complete assigned texts, not just highlighted review pages. That advice is worth following literally. The publications have different publication years, and those years are reference dates, not exam-release dates, so do not read them as signals of when the exam changes.
| Publication | Best Domain Fit |
|---|---|
| HHS, Airborne Allergens: Something in the Air (2003) | Domains 1 and 2 |
| HUD, Healthy Homes Issues: Asthma (2012) | Domains 1 and 5 |
| CDC, Healthy Housing Reference Manual, chapter 5 (2006) | Domains 2, 3, and 5 |
| EPA, Exposure Factors Handbook, chapter 19 (updated 2018) | Domains 3 and 5 |
| Levetin, Methods for Aeroallergen Sampling (2004) | Domains 2 and 4 |
| APHL, Environmental Laboratories and Indoor Air Testing: A Primer (2015) | Domains 4 and 6 |
| HUD, Vacuum Dust Sample Collection Protocol for Allergens (2008) | Domain 4 |
The mapping above is a study aid, not an official crosswalk. Many publications touch several domains, so read them whole. For a consolidated overview of what to carry into exam day, see the CEAI cheat sheet.
Sequencing the Domains in Your Prep
Because no domain weights are published, an even-handed schedule that follows the logical flow of an investigation works well. Start with the biology, move through the building, then into method and judgment. Adjust the order based on your own gaps, and use the full approach in the CEAI study guide for broader planning.
Health Context and Allergen Sources
- Read the HHS and HUD asthma publications in full (Domain 1)
- Build a table of allergen types, reservoirs, and favorable conditions (Domain 2)
The Building as a System
- Work through the CDC housing manual and EPA exposure chapter (Domain 3)
- Trace how moisture and ventilation drive allergen accumulation
Methods and Equipment
- Study the HUD vacuum dust protocol step by step (Domain 4)
- Read the Levetin and APHL pieces and note method limitations
Judgment, Guidance, and Practice
- Practice interpretation and remediation scenarios (Domain 5)
- Review the authority and role of each source (Domain 6)
- Take timed 100-question practice sessions across all domains
Key Takeaway
Schedule Domain 4 earlier if your day-to-day work does not involve hands-on sampling, and Domain 3 earlier if your background is lab-based. Your weakest operational area is where a closed-book exam will expose you. Use the CEAI practice tests to find gaps before they find you.
Eligibility, Fees, and Logistics That Frame Your Prep
Exam preparation sits inside a larger application process, and several details shape your timeline. ACAC requires either a qualifying two-year degree (or its stated equivalent of 15 credit hours) plus at least one year of documented environmental allergen investigation experience, or no degree with at least two years of consulting experience in environmental allergen investigations plus a high-school diploma or GED. Qualifying education includes microbiology, engineering, science, architecture, industrial hygiene, or a related science. You submit four project sheets, transcripts if claiming education credit, the online application, and required email verifications. No training course is mandatory. Experience verification, the examination, and unanimous board approval are separate certification requirements. Our requirements guide covers this in more detail.
On cost, ACAC lists a USD 100 examination component and a USD 100 retake. Its general accredited-certification schedule shows USD 500 initially, made up of USD 400 for certification plus USD 100 for the examination, and USD 400 per two-year renewal. These are published category rates rather than a verified CEAI-specific quotation, so confirm your total with ACAC before budgeting. See CEAI certification cost for the full breakdown.
The credential is valid for two years. Current recertification procedures describe 40 recertification credits per term, made up of 10 for continued field activity and 30 hours of professional development, with records retained for possible audit. For scheduling questions, see CEAI exam dates.
Finally, keep the historical numbers in perspective. ACAC's activity report for December 31, 2025 shows a CEAI examination pass ratio of 50%, two applicants in 2025, and one current certification at that date. With so few applicants, and with totals that can include licensing-only candidates, this is not a verified first-attempt or long-run pass rate, and it does not predict 2026 results. The CEAI pass rate article discusses how to read it responsibly.
Frequently Asked Questions
Six: the allergic response in humans; types of allergens and their presence in the built environment; principles of the built environment; investigation principles, procedures, and equipment; allergen evaluation and remediation strategies; and guidelines, regulations, and standards.
No. The reviewed ACAC sources do not publish percentage weights for the six domains, so you should prepare across all of them rather than rely on any claimed split.
The exam has 100 closed-book, computer-delivered multiple-choice questions with at least four options each, a 3-hour limit, and a 75% passing score set by the Modified Angoff Method. Scores are immediate.
ACAC assigns seven publications from HHS, HUD, CDC, EPA, APHL, and Levetin, and recommends reading the complete texts instead of only highlighted pages. Start with the HUD vacuum dust protocol and the APHL laboratory primer for the investigation domain.
No. They share a study packet, but the CEAC has its own format and higher experience requirements that do not apply to the investigator credential. Plan around the CEAI details described here, and review What Is CEAI? if you need a refresher on the credential itself.
With the six domains mapped to the assigned readings and your own project experience, you have a defensible structure for preparing. When you are ready to test yourself under timed conditions, the CEAI Exam Prep practice test site offers a way to pressure-test every domain.