- The trade exam is 90 questions in 240 minutes, and you need 70% to pass.
- Air Distribution Systems carries 25 of 90 items - the single biggest domain on the exam.
- The trade exam fee is $92; Business and Law is a separate $92 exam.
- Unlimited candidates must document experience on equipment above 25 tons and 500,000 Btu/h.
Exam Snapshot: Format, Fees, and Timing
This cheat sheet is built as a one-page-style reference for the Oklahoma Mechanical Trade License Exam - HVACR Contractor Unlimited, administered under the Oklahoma Construction Industries Board (CIB) and delivered through PSI Services LLC. If you want the full narrative walkthrough of what to expect, pair this page with the OK-MECH Study Guide 2026; this article is meant for quick recall in the days before test day.
- Trade exam format: 90 computer-based questions, 240 minutes, 70% passing score.
- Experimental items: PSI may insert up to 10 unscored questions; the time to answer them does not count against your 240-minute clock.
- Trade exam fee: $92 per attempt.
- Business and Law exam: separate 50-question exam, 120 minutes, also 70% to pass, also $92.
- Current bulletin: effective August 31, 2026, published by PSI.
The Six Domains at a Glance
The trade exam's 90 questions are split across six official subject areas. Memorizing the relative weight of each domain is one of the highest-leverage things you can do before test day - it tells you exactly where extra review hours pay off. For a deeper breakdown of what each domain actually tests, see the OK-MECH Exam Domains 2026 guide.
| Domain | Approx. Items | Share of Exam |
|---|---|---|
| Domain 1: Electrical Knowledge and Controls | 15 | ~17% |
| Domain 2: Natural Gas | 12 | ~13% |
| Domain 3: Air Distribution Systems | 25 | ~28% |
| Domain 4: Refrigeration and Air Conditioning Systems | 20 | ~22% |
| Domain 5: Heating Systems | 15 | ~17% |
| Domain 6: Safety | 3 | ~3% |
Domain 3: Air Distribution Systems
This is the largest domain at 25 of 90 items, so it deserves the largest single block of your review time. Candidates should be comfortable moving between duct sizing tools and code-based airflow requirements without hesitation.
- Practice reading and applying an ACCA ductulator quickly, since it's an allowed open-book reference.
- Review static pressure, CFM calculations, and duct sizing logic for both supply and return systems.
- Expect scenario-style questions that ask you to size or troubleshoot a distribution system, not just define terms.
Domain 4: Refrigeration and Air Conditioning Systems
At 20 items, this domain is the second-largest and pulls heavily from the specified refrigeration textbook.
- Know refrigeration cycle fundamentals cold - compression, condensing, metering, and evaporation stages.
- Be ready for equipment-sizing and troubleshooting questions tied to Unlimited-scale tonnage (above 25 tons).
- Cross-check textbook edition dates before test day - more on that below.
Domain 1: Electrical Knowledge and Controls
Tied with Heating Systems at 15 items, this domain covers the control-side logic that keeps HVACR equipment running safely.
- Focus on control circuits, relays, and basic troubleshooting logic rather than deep electrical theory.
- Expect application questions: "what happens if this component fails" style items are common in this format.
Domain 5: Heating Systems
Also 15 items. This domain overlaps with Natural Gas but focuses more on combustion appliances, venting, and heat exchanger logic.
- Review furnace staging, ignition systems, and venting requirements referenced in the mechanical/fuel-gas codes.
- Know the difference between code requirements for various appliance categories.
Domain 2: Natural Gas
12 items. Draws directly from the fuel-gas code portions of your open-book references.
- Practice locating gas piping sizing tables and appliance clearance requirements quickly under time pressure.
- Know venting and combustion air requirements by appliance type.
Domain 6: Safety
Only 3 items, but don't skip it - these are typically direct, fact-based questions drawn from the OSHA reference material.
- A quick pass through OSHA basics on the day before the exam is usually enough to lock in these points.
If you're still deciding how much total prep time this format warrants, the How Hard Is the OK-MECH Exam? guide breaks down difficulty by domain in more detail, and the OK-MECH Pass Rate 2026 article covers what the available data shows about outcomes.
Open-Book References You're Allowed to Use
This exam is open-book, but only with specific, approved materials - bringing the wrong edition or unauthorized notes can create problems at check-in. Here's the reference list to have tabbed and ready:
- The specified mechanical code and fuel-gas code editions currently allowed under the bulletin
- The designated refrigeration textbook
- An OSHA reference
- ACCA Manual N
- Mathematics for Plumbers and Pipefitters
- An ACCA ductulator
Key Takeaway
Pre-highlighting and permanent tabs in your reference books are allowed. Handwritten notes are prohibited. A PSI-compliant non-programmable calculator is permitted - bring one you've practiced with, not one you're grabbing for the first time at the test center.
Code Transitions to Track for 2026
Because this bulletin spans a code-edition changeover, the allowed reference editions shift mid-year. Missing this window is a common, avoidable mistake - verify your books against the dates below before you schedule.
- 2024 IMC and IFGC: become usable starting September 14, 2026.
- 2018 IMC/IFGC editions: cease to be allowed December 14, 2026.
- Modern Refrigeration and Air Conditioning, 22nd edition: became usable August 13, 2026.
- 20th edition of that same title, plus Refrigeration and Air Conditioning Technology, 5th edition: cease to be allowed November 1, 2026.
Eligibility and the Money Side
The HVACR Contractor Unlimited path has its own eligibility layer beyond just sitting for the exam. Applicants must be at least 18 years old, meet the mechanical journeyman experience requirements plus one additional qualifying year, and be an owner, partner, officer, or permanent employee of a mechanical firm.
- Standard experience-only route: totals four years; approved education can reduce the journeyman experience component.
- Unlimited-specific documentation: qualifying work must be shown on equipment above 25 tons and 500,000 Btu/h - this is what separates Unlimited from more limited mechanical scopes.
- Experience certifications and school records are required as supporting documentation with your application.
On the cost side, keep the trade exam fee separate in your head from the licensing fees:
| Item | Amount |
|---|---|
| Trade exam fee (per attempt) | $92 |
| Business and Law exam fee | $92 |
| Initial CIB application fee | $30 |
| Initial CIB license fee | $300 |
| Total initial application/license payment | $330 |
| Required surety bond | $5,000 |
| Required commercial general liability insurance | $50,000 |
| Annual contractor renewal fee | $200 |
For a fuller line-item explanation of every fee and what it actually pays for, see the OK-MECH Certification Cost 2026 breakdown. And if you're weighing whether the licensing investment makes sense against your career goals, the Is the OK-MECH Certification Worth It? ROI analysis and OK-MECH Salary Guide 2026 are good companion reads. Both required exam portions must be passed within three years of eligibility approval under CIB rules, so don't let one attempt sit for too long before scheduling the retake.
Retakes, Renewal, and CE
Life happens, and not every candidate passes on the first attempt - knowing the retake rules ahead of time keeps a failed attempt from derailing your timeline.
- First failure: a 30-day waiting period before you can retest.
- Subsequent failures: a 90-day waiting period applies.
- Three-year window: both the trade exam and Business and Law exam must be passed within three years of eligibility approval.
Once licensed, renewal happens annually in your birth month, with a $200 contractor renewal fee. Continuing education is set at six approved hours every 36 months, with an initial three-year examination exemption after you first pass. This is a lighter CE cadence than many trades require, but it's still worth calendaring so it doesn't sneak up on you.
A One-Week Final Review Plan
If you already have a full study plan underway (see the OK-MECH Study Guide if not), here's how to allocate your last seven days by domain weight rather than by generic review habits.
Air Distribution Systems + Refrigeration
- Drill duct sizing and ductulator use until it's automatic.
- Review refrigeration cycle diagrams and equipment troubleshooting scenarios.
Electrical Controls + Heating Systems
- Rehearse control-circuit failure scenarios.
- Review combustion, venting, and heat exchanger code requirements.
Natural Gas
- Practice locating gas piping sizing tables under a timer.
Safety + Full Mixed Review
- Quick OSHA reference pass - only 3 items, but easy points.
- Take a full 90-question timed mock covering all six domains.
Reference Check + Rest
- Confirm you have the correct code editions and textbook editions per the transition dates above.
- Verify calculator is PSI-compliant and reference books are tabbed, not handwritten on.
You can run more mixed-domain drills against our full practice test platform to simulate the 240-minute pacing before you sit for the real thing. Repeated timed runs on our practice site are also the fastest way to find which domain is quietly costing you the most points.
FAQ
The trade exam has 90 computer-based questions with a 240-minute time limit, and you need 70% correct to pass. PSI may add up to 10 unscored experimental questions that don't count against your time.
Air Distribution Systems, worth 25 of the 90 items, is the largest domain by far. Refrigeration and Air Conditioning Systems at 20 items is the second priority. Safety, at just 3 items, needs only a light review pass.
No, it's a separate exam: 50 questions in 120 minutes, requiring 70% to pass, with its own $92 fee. Both the trade exam and Business and Law exam must be passed within three years of eligibility approval.
Beyond the standard mechanical journeyman requirements plus one additional qualifying year, Unlimited applicants must document work on equipment above 25 tons and 500,000 Btu/h, along with experience certifications and applicable school records.
No. Handwritten notes are prohibited. You can pre-highlight and use permanent tabs in your approved reference books, and a PSI-compliant non-programmable calculator is allowed.
For a broader orientation before diving into domain-level prep, start with What Is OK-MECH? or the OK-MECH Certification overview, then come back to this cheat sheet as your final-review anchor.