IAQ-T Exam Domains 2026: Complete Guide to All 5 Content Areas

How the Five Domains Are Built

The Indoor Air Quality Technician (IAQ-T) credential is issued by the International Certification Board (ICB), the certification arm of the sheet metal industry. Its written exam is organized around five weighted examination objectives published in the Indoor Air Quality Technician Knowledge Base inside the ICB Certification Manual (cover version 241024, approved October 24, 2024). Those five lines are exam objectives, not course modules, which is an important distinction: a training class may teach topics in a different order or grouping than the exam samples them.

If you are new to the credential itself, start with What Is IAQ-T Certification? for the big picture, then return here for the blueprint. This guide focuses on what each domain asks of a technician who verifies ventilation and indoor air quality performance in buildings, and how to weight your preparation accordingly.

Domain Weights at a Glance

The weights below total 100% of the exam blueprint. Because 70 items are scored, the weights give you a rough sense of how heavily each area is sampled, though the exam publishes percentages rather than guaranteed per-domain item counts.

Notice the shape of the blueprint: it is practice-heavy. The two largest domains, Testing and Visual Inspection and HVAC Systems, combine for 51%. Candidates with a strong equipment background but little experience writing field reports tend to be surprised by how much Documentation counts. For a sense of how this affects difficulty, see How Hard Is the IAQ-T Exam?

Domain 3: Testing and Visual Inspection (27%)

This is the single largest domain, and it is where the credential's purpose shows most clearly. A technician is expected to verify that a building's ventilation and air quality conditions match what the design and applicable standards call for, and to spot problems that instruments alone will not reveal.

Why visual inspection carries real weight

Visual inspection is easy to underestimate because it sounds informal. On the exam, it is a structured skill: knowing what a healthy component looks like, which defects signal an air quality risk, and which observations belong in a report. Questions may describe a condition and ask for its most likely consequence or the correct next step. Practice reading descriptions of conditions the way you would read a site walk-through, and be ready to connect a physical symptom to a ventilation or contamination cause.

Worked-reasoning habits

Calculation items at technician level are generally about applying a relationship correctly, not advanced derivation. Be comfortable rearranging airflow, volume and time relationships, and comfortable estimating outside-air fraction from mixed, return and outdoor conditions. Practice stating units at every step; many wrong answers on this type of item come from unit mismatches rather than conceptual gaps.

Domain 1: HVAC Systems (24%)

The second-largest domain tests whether you understand the systems you will be verifying. You do not need to be a design engineer, but you do need to read how air moves through a building and what each major component does to ventilation and air quality.

Many candidates come to this exam from sheet metal trades and bring strong ductwork instincts. The exam's HVAC questions still lean toward performance and verification: not just "what is this component," but "what happens to ventilation if this component fails, is mis-set, or is out of sequence." If you are working through the official training pathway, our IAQ-T training overview explains how coursework lines up with this knowledge.

Domain 2: Instrumentation (19%)

Instrumentation is about the tools of the trade and, just as importantly, about trusting the numbers they produce. The domain rewards candidates who understand what an instrument measures, how it can mislead, and how to keep it reliable.

A common trap is treating an instrument reading as automatically correct. Expect items where the right answer involves questioning a reading: a sensor placed in a poor location, an instrument outside its useful range, or a result that contradicts other observations. This habit connects directly to the Documentation domain, because a defensible report records how the measurement was made, not just the number.

Domain 5: Documentation (18%)

Documentation is easy to dismiss as paperwork, yet it is worth almost as much as Instrumentation. In ventilation verification work, the report is the product: it is how a building owner, engineer or contractor learns what you found and what needs to happen next.

Domain 4: Air Contaminants in Construction (12%)

The smallest domain still deserves attention, because it covers a distinctive part of IAQ-T work: protecting air quality during construction and renovation, and recognizing contaminant sources introduced by building activity.

At 12%, this domain will not make or break your result alone, but it can supply several straightforward points if you have reviewed it. Because it is smaller, many candidates give it too little time and miss easy items.

Reference Standards Named in the Outline

The knowledge base names specific standards and editions. Study the editions the outline names, even if newer editions exist, because the exam is built from the published outline.

The proctor identifies approved references for the exam, and authorized electronic reference viewing is allowed under exam-security restrictions. That does not mean unrestricted open-book access, so learn the key relationships rather than counting on looking everything up. For a condensed review, our IAQ-T cheat sheet collects the must-know facts.

What the Exam Looks Like and How It Is Scored

The IAQ-T exam is a written, proctored exam delivered online or on paper through an ICB-designated proctor and site, usually arranged through the local JATC or training-center coordinator. It is separate from the practical component associated with TABB certification; the IAQ-T is a written exam.

• Items: 75 total, of which 70 are scored and 5 are unscored beta items.
• Passing: at least 53 of the 70 scored items. You cannot tell which five items are unscored, so treat every question seriously.
• Time: no national numeric time limit was verified in current issuer materials. A local SMART Local 2 notice describes a 2.5-hour ICB testing event shared by candidate groups, but confirm your own session length with your coordinator.
• Fees: initial and renewal certification fees are listed at USD 0 for eligible Technician applicants under the ICB Fee Schedule; separate training, travel or local charges are not universal. See IAQ-T certification cost for details.
• Retests: waits are 30 days for the first retest, 60 for the second and 90 for subsequent attempts; written testing must occur within one year of application approval.

For the exact threshold and how to interpret it, read IAQ-T passing score. Note that a passing score is not the same thing as a pass rate; no pass rate was found in the reviewed official sources, as explained in IAQ-T pass rate: what the data shows.

Sequencing Your Prep Around the Weights

You do not need an elaborate system. The simplest approach is to let the domain weights decide when and how long you study each area, and to put practice questions at the end of every block. A full approach is covered in the IAQ-T study guide; here is a blueprint-driven outline.

Adjust the length to your background. A tradesperson fluent in ductwork may compress Week 1 and spend longer on Documentation; someone strong on writing but newer to mechanical systems will do the opposite.

Frequently Asked Questions

Mastering the blueprint means respecting its weights: put your deepest practice into Testing and Visual Inspection and HVAC Systems, keep Instrumentation and Documentation sharp, and do not skip Air Contaminants in Construction. When you are ready to test yourself against all five areas, take a timed set on our main practice test site.