- The June 15, 2026 Prov outline splits the 100-question TN-CMC exam across 13 domains, weighted 4 to 18 items.
- Air Distribution and Vents (Domain 11) carries 18 items - the single largest content area on the exam.
- Equipment and Refrigerants and Oils (Domains 9 and 10) each carry 10 items, making them the next priority.
- The exam is open-book, computer-delivered, and requires a 73% passing standard on 100 scored questions.
Overview of the TN-CMC Blueprint
Every candidate preparing for the Tennessee Full Mechanical Contractor (CMC) Exam eventually asks the same question: what, exactly, is on the test? The Tennessee Board for Licensing Contractors answers that through Prov's official content outline, dated June 15, 2026, which governs the CMC classification covering both plumbing and HVAC scopes of work. That outline lists exactly 100 questions distributed across 13 named domains, each pulling from a defined set of reference texts.
Unlike vague "study everything" advice, the TN-CMC blueprint is precise: item counts per domain are published, the reference books are named, and the testing rules (open-book, computer-delivered, calculator permitted) are spelled out. This article walks through all 13 domains in their official order, explains why Air Distribution and Vents dominates the weighting, and shows how the domain structure should shape your prep schedule. For a broader look at how difficult the exam feels in practice, see How Hard Is the TN-CMC Exam? Complete Difficulty Guide 2026, and for the pass/fail mechanics themselves, see TN-CMC Passing Score 2026: Exactly What You Need to Pass.
All 13 Domains, Item by Item
Here is the official item allocation, in Domain 1-13 order, as published in the CMC content outline:
| Domain | Name | Item Count |
|---|---|---|
| 1 | General Knowledge | 6 |
| 2 | Code Requirements | 5 |
| 3 | Fuel Gas Systems | 8 |
| 4 | Safety | 8 |
| 5 | Controls | 4 |
| 6 | Electrical Concepts | 4 |
| 7 | Piping | 8 |
| 8 | Load Calculations | 5 |
| 9 | Equipment | 10 |
| 10 | Refrigerants and Oils | 10 |
| 11 | Air Distribution and Vents | 18 |
| 12 | Fire Protection | 4 |
| 13 | Sprinkler Systems | 10 |
Add those figures and you get 100 questions - the full scored exam. No domain is optional, but the spread is far from even. Six domains (11, 9, 10, 13, 3, 7, 4) together account for a majority of the exam, while domains like Controls, Electrical Concepts, and Fire Protection sit at just 4 items apiece. That imbalance is the single most important fact for building an efficient prep plan, and it's the backbone of the timed, domain-weighted approach described in the TN-CMC Study Guide 2026: How to Pass on Your First Attempt.
Key Takeaway
Don't split study time evenly across 13 domains. Allocate time roughly in proportion to item count - Air Distribution and Vents deserves far more hours than Controls or Fire Protection.
The Three Biggest Domains and Why They Matter
Three domains carry the most weight on the CMC exam and deserve the most attention in your prep timeline.
Domain 11: Air Distribution and Vents (18 items)
This is the largest domain by a wide margin - nearly one-fifth of the entire exam. It covers duct systems, venting requirements for combustion appliances, and airflow principles that tie directly into IMC 2021 and IFGC 2021 provisions.
- Duct sizing, layout, and material requirements referenced in the mechanical code
- Venting configurations for gas-fired equipment, including clearance and termination rules
- Airflow concepts that connect to Load Calculations (Domain 8) and Equipment (Domain 9)
Domain 9: Equipment (10 items)
Equipment questions test practical familiarity with HVAC and plumbing equipment selection, installation clearances, and manufacturer/code compliance - the kind of knowledge reinforced by HVAC Basics for Contractors, fourth edition.
- Proper equipment selection based on load and application
- Installation clearances and access requirements
- Manufacturer specifications cross-referenced against code minimums
Domain 13: Sprinkler Systems (10 items)
Tied with Equipment and Refrigerants and Oils for second-highest weight, this domain covers system components, water supply considerations, and installation basics relevant to a full mechanical contractor's scope.
- Sprinkler system components and their functions
- Water supply and pressure fundamentals
- Coordination points between fire protection and mechanical systems
Together, these three domains represent 38 of the 100 scored questions. Anyone building a study calendar without accounting for that concentration is setting themselves up for uneven readiness - a mistake covered in more depth in TN-CMC Cheat Sheet 2026: One-Page Review of Must-Know Facts.
The Smaller-Weighted Domains
The remaining ten domains range from 4 to 10 items each. They still matter - missing them entirely can cost a passing score - but they require less repetition to master.
Domain 10: Refrigerants and Oils (10 items)
Refrigerant handling, oil compatibility, and system charging concepts. This domain rewards familiarity with equipment-side mechanics covered in the HVAC Basics text.
Domains 3 and 7: Fuel Gas Systems and Piping (8 items each)
Fuel gas systems draw heavily on IFGC 2021 - pipe sizing, appliance connections, and shutoff requirements. Piping overlaps both plumbing and HVAC scopes, covering materials, joining methods, and support spacing.
Domain 4: Safety (8 items)
Jobsite safety practices, hazard recognition, and protective procedures relevant to mechanical contracting work.
Domains 1, 2, and 8: General Knowledge, Code Requirements, Load Calculations (6, 5, 5 items)
General Knowledge sets the foundation; Code Requirements tests broad familiarity with IMC and IFGC structure; Load Calculations checks sizing math for heating and cooling loads.
Domains 5, 6, and 12: Controls, Electrical Concepts, Fire Protection (4 items each)
The lightest-weighted domains. Controls covers thermostats and control sequences; Electrical Concepts covers basic circuits relevant to mechanical equipment; Fire Protection covers general fire-safety principles distinct from the more heavily weighted Sprinkler Systems domain.
Reference Materials Behind the Domains
The June 15, 2026 outline names three source texts that map onto these 13 domains:
- IMC 2021 (International Mechanical Code) - underpins Code Requirements, Air Distribution and Vents, Piping, and Load Calculations content.
- IFGC 2021 (International Fuel Gas Code) - the primary source for Fuel Gas Systems questions and portions of venting-related Air Distribution content.
- HVAC Basics for Contractors, fourth edition - supports Equipment, Refrigerants and Oils, Controls, and general HVAC concepts across several domains.
Because the exam is open-book and computer-delivered through Prov, familiarity with where topics live inside these three texts matters more than rote memorization. Prov's testing rules allow advance highlighting and permanent tabs in your books, but not handwritten notes, loose papers, or movable tabs - and only a simple four-function calculator is permitted. Building your tab system around the domain weights above (heavy tabs for Air Distribution and Vents, Equipment, Refrigerants and Oils, and Sprinkler Systems) is far more useful than tabbing every page equally.
Key Takeaway
Tab your IMC 2021, IFGC 2021, and HVAC Basics books proportionally to domain weight - Air Distribution and Vents alone justifies the densest tabbing since it's worth 18 of 100 questions.
For a full explanation of what counts as an approved reference and how the open-book format changes your prep strategy, see TN-CMC Study Guide 2026: How to Pass on Your First Attempt. For a plain breakdown of the exam's pass threshold itself, see TN-CMC Passing Score 2026: Exactly What You Need to Pass.
Mapping Study Weeks to Domain Weight
Rather than a generic weekly template, the most efficient TN-CMC prep schedule assigns study time proportional to each domain's item count. Here's one way to structure a multi-week plan around the 13 domains:
Air Distribution and Vents + Code Requirements
- Work through duct sizing and venting rules in IMC 2021 and IFGC 2021
- Build tabs for the 18-item domain first, since it carries the most risk if skipped
Equipment, Refrigerants and Oils, Sprinkler Systems
- Review equipment selection and clearance rules from HVAC Basics
- Cover refrigerant handling and sprinkler system components together, since both carry 10 items
Fuel Gas Systems, Piping, Safety
- Focus on IFGC 2021 pipe sizing and appliance connection rules
- Pair Piping with Safety, since jobsite scenarios often reference both
Remaining light domains + full-length review
- Cover General Knowledge, Load Calculations, Controls, Electrical Concepts, and Fire Protection
- Run a full 100-question timed simulation reflecting the 13-domain weighting
This is the only place methodology enters the picture - and it's tied directly to the blueprint, not a generic template. If you want a deeper look at how this timeline should adapt based on how much time you realistically have, TN-CMC Study Guide 2026: How to Pass on Your First Attempt covers pacing in more detail, and How Hard Is the TN-CMC Exam? Complete Difficulty Guide 2026 discusses which domains tend to surprise candidates.
How Domains Connect to Registration and Fees
Understanding the domain structure only matters if you're actually eligible to sit for the exam. Tennessee's Board for Licensing Contractors requires preapproval before scheduling: applicants must be at least 18 years old and document three years of plumbing experience (the Board's form accepts specified alternative documentation, including qualifying engineering-degree paperwork). Full eligibility details are covered in TN-CMC Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Once preapproved, candidates schedule through Prov, which takes over new exam scheduling beginning July 1, 2026 (already-scheduled PSI appointments remain honored through September 2026). The exam itself is computer-delivered with options for test centers or Examroom.ai remote proctoring, and each attempt carries a Prov examination fee of $53, separate from the Board's $50 CMC preapproval fee. For the complete cost picture - including the $250 initial license fee and $200 biennial renewal - see TN-CMC Certification Cost 2026: Complete Pricing Breakdown.
Note also that new contractor applicants take a separate Tennessee Business and Law examination, and the qualifying agents for the trade exam and the business-and-law exam do not need to be the same person. A qualifying agent may be an owner, officer, or full-time employee of the applicant business. Exam results are typically accepted for two years, giving candidates a reasonable window to complete the rest of the licensing process, including financial qualification, insurance documentation, and workers-compensation coverage.
If you're still deciding whether the credential fits your career path, Is the TN-CMC Certification Worth It? Complete ROI Analysis 2026 and TN-CMC Salary Guide 2026: Complete Earnings Analysis look at the bigger picture beyond exam content. And once you're ready to test your recall against realistic, domain-weighted questions, the practice platform at the main TN-CMC practice test site mirrors this 13-domain structure directly.
Frequently Asked Questions
There are 13 domains: General Knowledge, Code Requirements, Fuel Gas Systems, Safety, Controls, Electrical Concepts, Piping, Load Calculations, Equipment, Refrigerants and Oils, Air Distribution and Vents, Fire Protection, and Sprinkler Systems.
Air Distribution and Vents (Domain 11) is the largest, with 18 of the 100 total questions on the June 15, 2026 Prov content outline.
Yes. It's computer-delivered and open-book, with a 73% passing standard. Prov allows advance highlighting and permanent tabs in reference books, but not handwritten notes, loose papers, or movable tabs. A simple four-function calculator is permitted.
The current outline lists IMC 2021, IFGC 2021, and HVAC Basics for Contractors, fourth edition, as the source texts. Always confirm against the current Prov bulletin before finalizing which editions to buy.
No. Weighting ranges from 4 items (Controls, Electrical Concepts, Fire Protection) up to 18 items (Air Distribution and Vents), so study time should be allocated proportionally rather than evenly across domains.