- What OK-MECH Actually Stands For
- Who Administers the Exam
- Exam Format and Question Style
- The Six Content Domains
- Eligibility and the Unlimited Tier
- Fees and Registration Mechanics
- Allowed References and Materials
- Who Actually Needs OK-MECH
- Mapping Study Time to the Outline
- Frequently Asked Questions
- OK-MECH refers to the Oklahoma Mechanical Trade License Exam for the HVACR Contractor Unlimited classification.
- The trade exam has 90 questions in 240 minutes, and 70% is required to pass.
- Air Distribution Systems is the heaviest domain at 25 of 90 questions.
- Unlimited status requires documented work on equipment above 25 tons and 500,000 Btu/h.
What OK-MECH Actually Stands For
On this site, OK-MECH is shorthand for the Oklahoma Mechanical Trade License Exam - HVACR Contractor Unlimited. It is not a generic acronym borrowed from another state or another industry's certification program. It refers specifically to the trade-knowledge examination that a candidate must pass to qualify for an Unlimited HVAC/R Contractor license issued by the state of Oklahoma.
The word "Unlimited" matters. Oklahoma's mechanical contractor licensing structure includes tiers based on equipment size, and the Unlimited classification permits work on the largest residential and commercial systems without a capacity ceiling. That distinction is baked into the exam's eligibility rules, which is why OK-MECH candidates must document experience on equipment above 25 tons of cooling capacity and 500,000 Btu/h of heating input before they can sit for the test.
Who Administers the Exam
Two organizations sit behind the OK-MECH name. The Oklahoma Construction Industries Board (CIB) is the state agency that sets licensing requirements, approves applications, and issues the actual contractor license. PSI Services LLC is the third-party testing provider that builds, schedules, and proctors the computer-based exam itself.
This two-party structure explains why candidates deal with two different processes: CIB paperwork (application, experience verification, bonding, insurance) and PSI logistics (scheduling, testing center rules, score reporting). Understanding this split early avoids a lot of confusion later in the licensing journey - a topic covered in more depth in the OK-MECH Requirements guide.
Exam Format and Question Style
The OK-MECH trade exam is a fixed, no-frills format:
- 90 scored questions delivered as computer-based testing
- 240 minutes total time allowed
- 70% required to pass
- Up to 10 unscored experimental questions may be added by PSI; time spent on these does not count against the 240-minute limit
Because experimental items are unscored but indistinguishable from scored ones on screen, candidates should treat every question with equal seriousness rather than trying to guess which ones "don't count." There is a separate, shorter Business and Law exam - 50 questions in 120 minutes, also requiring 70% - but it is a distinct test with its own fee and its own content, and it is not part of the trade-knowledge domains discussed here.
Key Takeaway
Budget your 240 minutes across all 90 questions rather than racing through early domains; unscored experimental items mean the pacing math isn't as simple as "240 minutes ÷ 90 questions."
The Six Content Domains
OK-MECH's trade knowledge is organized into six official subject areas. The allocation is uneven, and the imbalance should directly shape how a candidate divides study time.
Domain 3: Air Distribution Systems - 25 questions
The single largest domain on the exam. Covers ductwork sizing, airflow principles, and distribution equipment used in HVAC/R installations.
- Expect the heaviest question density here - nearly 28% of the exam
Domain 4: Refrigeration and Air Conditioning Systems - 20 questions
Refrigerant cycles, cooling equipment, and system components for both refrigeration and air conditioning applications.
- Second-largest domain; pairs naturally with Air Distribution content
Domain 1: Electrical Knowledge and Controls - 15 questions
Electrical fundamentals as applied to HVAC/R controls and equipment operation.
Domain 5: Heating Systems - 15 questions
Heating equipment, combustion basics, and system design considerations tied to Oklahoma's fuel-gas and mechanical codes.
Domain 2: Natural Gas - 12 questions
Gas piping, appliance connections, and code-driven requirements for natural gas systems in mechanical installations.
Domain 6: Safety - 3 questions
The smallest domain numerically, but safety knowledge underpins correct answers across several other domains as well.
Together these six areas total the full 90-question outline (15 + 12 + 25 + 20 + 15 + 3 = 90). For a deeper breakdown of what each domain actually tests, see the OK-MECH Exam Domains 2026 guide.
Eligibility and the Unlimited Tier
Sitting for OK-MECH isn't open to just anyone with HVAC experience. Applicants must:
- Be at least 18 years old
- Meet the mechanical journeyman experience requirements, plus one additional year of qualifying experience
- Be an owner, partner, officer, or permanent employee of a mechanical firm
- Document qualifying work on equipment above 25 tons and 500,000 Btu/h to support the Unlimited classification
The standard experience-only path totals four years, though approved education can reduce the journeyman experience component. Experience certifications and applicable school records must be submitted as part of the CIB application. Full detail on documentation and timelines is available in the OK-MECH Requirements 2026 breakdown.
Fees and Registration Mechanics
Understanding the money side of OK-MECH prevents surprises during registration:
| Item | Amount |
|---|---|
| Trade exam fee (per attempt) | $92 |
| Business and Law exam fee | $92 |
| CIB application fee | $30 |
| CIB license fee | $300 |
| Annual contractor renewal fee | $200 |
The initial CIB application/license payment therefore totals $330 ($30 application plus $300 license), separate from the $92 trade exam fee and the $92 Business and Law fee. Retakes after a failed attempt require a 30-day wait for the first failure and 90 days for subsequent failures, and both required portions (trade and Business and Law) must be passed within three years of eligibility approval under CIB rules. Once licensed, renewal is annual in the applicant's birth month, and continuing education of six approved hours every 36 months applies after an initial three-year exemption. A full cost walkthrough lives in the OK-MECH Certification Cost 2026 breakdown.
Allowed References and Materials
OK-MECH is partially open-book, which changes how candidates should prepare. Permitted references include specified mechanical and fuel-gas codes, a refrigeration textbook, an OSHA reference, ACCA Manual N, Mathematics for Plumbers and Pipefitters, and an ACCA ductulator. Pre-highlighting and permanent tabs in these references are allowed, but handwritten notes are prohibited. A PSI-compliant non-programmable calculator is also permitted.
Code editions matter and change on a schedule. The 2024 IMC and IFGC become usable September 14, 2026, while the 2018 editions stop being allowed December 14, 2026 - creating an overlap window candidates should be aware of. Similarly, Modern Refrigeration and Air Conditioning, 22nd edition, became usable August 13, 2026, and its 20th edition along with the listed Refrigeration and Air Conditioning Technology, 5th edition, cease to be allowed November 1, 2026. The current PSI bulletin governing all of this is effective August 31, 2026, so candidates should always check which edition is valid for their scheduled test date rather than assuming last year's list still applies.
Key Takeaway
Practice navigating your actual allowed references before test day - knowing where a table sits in your ACCA Manual N saves real minutes inside the 240-minute window.
Who Actually Needs OK-MECH
OK-MECH is aimed squarely at people pursuing Unlimited HVAC/R contractor status in Oklahoma - not entry-level technicians and not journeyman-only candidates. Typical candidates include:
- Experienced HVAC/R technicians moving into ownership or firm leadership roles
- Officers or partners of mechanical contracting firms who need to hold the license personally
- Journeyman-licensed workers who have logged the additional qualifying year and large-equipment experience needed for Unlimited scope
Because the license permits work without equipment-size restrictions, it tends to matter most for firms bidding larger commercial HVAC/R jobs. If you're weighing whether pursuing this license fits your career plans, the Is the OK-MECH Certification Worth It? ROI Analysis and OK-MECH Salary Guide articles address that question directly, and OK-MECH Jobs looks at where the license shows up in hiring.
Mapping Study Time to the Outline
Because the six domains carry very different weights, an even split across all six is inefficient. A more sensible approach allocates study blocks roughly in proportion to question count, front-loading Air Distribution Systems and Refrigeration and Air Conditioning Systems since together they make up half the exam.
Air Distribution Systems + Refrigeration/AC
- Work through ductwork sizing and airflow calculations using your ACCA Manual N and ductulator
- Review refrigerant cycle diagrams and equipment components
Electrical Knowledge and Heating Systems
- Practice control-circuit questions tied to HVAC equipment
- Study combustion basics and heating equipment code references
Natural Gas + Safety, then full mixed review
- Review gas piping and appliance connection rules from the applicable fuel-gas code edition
- Run full-length timed practice sets mixing all six domains
A short daily review session using flashcards for code section numbers and equipment terminology, combined with periodic full-length timed practice runs, tends to work better than marathon single-topic study sessions. For a complete week-by-week plan built around this exact domain weighting, see the OK-MECH Study Guide 2026. If you want a sense of where most candidates struggle before committing to a schedule, the How Hard Is the OK-MECH Exam? Difficulty Guide is a useful companion read, and you can start running practice questions anytime at the main OK-MECH practice test site.
Frequently Asked Questions
No. OK-MECH refers specifically to the HVACR Contractor Unlimited trade exam. Journeyman licensing has its own separate exam and requirements, though journeyman-level experience is a prerequisite building block toward Unlimited contractor eligibility.
No. Candidates must also pass the separate Business and Law exam, submit the CIB application with the $330 application/license payment, and meet bonding ($5,000 surety bond) and insurance ($50,000 commercial general liability) requirements before an active license is issued.
90 scored questions across six domains, with 240 minutes to complete the exam. PSI may add up to 10 unscored experimental questions, and time spent on those does not count against your 240 minutes.
Air Distribution Systems, at 25 of 90 questions, is the largest domain by a wide margin, followed by Refrigeration and Air Conditioning Systems at 20. Together they cover half the exam.
You must wait 30 days after a first failure before retaking, or 90 days after any subsequent failure. Both the trade exam and the Business and Law exam must be passed within three years of eligibility approval under CIB rules.