NV-C21 Exam Domains 2026: Complete Guide to All 22 Content Areas

Overview: Why the Domain Breakdown Matters

The Nevada State Contractors Board, through its testing administrator PSI Services LLC, structures the C-21 Refrigeration and Air Conditioning trade exam around 22 distinct content areas. Each area corresponds to a slice of the 85 scored questions you'll face in your 180-minute session. Knowing exactly how many questions come from each domain is the single most useful piece of intelligence a candidate can have before opening a study guide, because it tells you where your hours actually pay off.

This guide breaks down all 22 domains in the official order published in the current PSI candidate bulletin, along with the exact item count for each. If you haven't already reviewed the baseline numbers - passing threshold, time limit, retake rules - the NV-C21 Passing Score guide and the NV-C21 Requirements overview are good companion reads before you dig into domain-level planning.

The Full 22-Domain List with Item Counts

Here is the complete outline, in the order PSI presents it, with the number of scored items allocated to each domain. Together these add up to 85 - the full scored portion of the trade exam.

Remember that PSI may also insert up to 10 unscored, experimental questions into your session that count against your clock but not your score. You won't be told which items are experimental, so treat every question as if it counts - the domain weightings above only apply to the graded portion.

The Heavy Hitters: Fuel Systems, Refrigerants, Piping and Load Calculations

Four domains account for nearly a third of the entire exam. If your study time is limited, this is where it belongs first.

The Light Domains: One-Question and Two-Question Areas

On the other end of the scale, nine domains carry only one or two items each: Insulation, Sound-Vibration-and-Seismic-Control, and Machine Room each have exactly 1 item; Hydronics, Combustion Air, and Evaporative Cooling each have 2. These topics still deserve a working understanding - you can't skip them entirely - but they don't justify the same depth of preparation as Fuel Systems or Refrigerants.

Mid-weight domains worth noting include Controls (5 items), Chimneys, Flues and Vents (5 items), A/C and Heat Pump Equipment (4 items), Furnaces and Heaters (4 items), Solar (4 items), and Safety (4 items). These sit in a middle tier - not massive point sources, but frequent enough that a knowledge gap in any one of them can meaningfully affect your score. For a deeper look at how these weightings translate into overall exam difficulty, see How Hard Is the NV-C21 Exam?.

How the 85 Questions Are Actually Delivered

The NV-C21 trade exam is delivered as computer-based multiple-choice testing at a PSI test center, following Board approval of your application and an eligibility notice. You'll have 180 minutes to work through 85 scored questions plus up to 10 unscored experimental items PSI may include, meaning your effective question count could run as high as 95 within the same time window.

A minimum of 60 correct answers is required to pass. Because the pass threshold is fixed at 60 regardless of which questions turn out to be experimental, there's no way to identify or skip the unscored items - treat the entire test as live.

If you don't clear 60, retakes require a two-week waiting period. After three failed attempts, the application itself is voided, and you must wait 30 days before reapplying. This makes domain-by-domain preparation more than an academic exercise - it directly affects how many attempts and how much additional fee exposure you might face. The trade portion costs $95 alone, or $140 if bundled with the Construction Management Survey business-and-law package that most applicants also need. Full pricing details, including the $300 application fee and $600 biennial license fee, are broken down in the NV-C21 Certification Cost breakdown.

What You Can (and Can't) Bring Into the Exam

The NV-C21 trade exam is open book, but the allowed references are narrow and specific: only the 2018 Uniform Mechanical Code and the 2012 NFPA 54 National Fuel Gas Code may be brought into the testing room. No other code books, manufacturer manuals, or general references are permitted, so familiarity with these two exact editions is non-negotiable.

• Allowed: pre-highlighting, underlining, and permanent tabs placed in your code books ahead of time.
• Not allowed: handwritten notes, temporary tabs (like sticky flags you can remove and add), or any loose inserted material.
• Calculators: a silent, non-programmable calculator that meets PSI's restrictions is permitted.

Given how heavily Fuel Systems is weighted (10 items), your NFPA 54 tabbing strategy deserves as much attention as your UMC prep. Practice finding sizing charts and clearance tables under a timer, because fumbling through an unfamiliar tab system during the real exam wastes minutes you don't have.

Mapping the Domains to a Study Timeline

Rather than studying domains in the order PSI lists them, sequence your review by item weight - heaviest first, lightest last - and build in dedicated code-book navigation practice.

For a fuller walkthrough of pacing, retake rules, and how to structure practice sessions leading up to test day, see the NV-C21 Study Guide for a first-attempt pass. If you're still confirming eligibility before committing to a schedule, the four-years-of-experience requirement (with education substitution available for up to three years) is covered in detail in the requirements guide.

Who Sits for This Exam and Why the Domains Reflect It

The domain weightings aren't arbitrary - they mirror the scope of work a Nevada C-21 licensee is expected to perform in the field: gas and fuel line work, refrigerant handling, piping installation, load-driven equipment sizing, ductwork, and the full range of heating, cooling, and ventilation systems found in residential and light commercial buildings. Candidates typically come in with journeyman, foreman, supervising-employee, or existing contractor experience accumulated over the preceding fifteen years, which is why the exam assumes working familiarity rather than teaching concepts from zero.

Passing the trade exam is one part of licensure. Most applicants also complete the separate Construction Management Survey unless it's waived, and every applicant goes through experience verification, a financial and background review, and license bond and insurance requirements before the Nevada State Contractors Board issues a license. Licenses then renew biennially. If you're weighing whether this entire path is worth pursuing given the work involved, the ROI analysis and the earnings guide lay out the practical upside, while NV-C21 Jobs outlines the kind of work licensees typically pursue.

To sharpen your recall of the domain list and item counts fast, bookmark the NV-C21 Cheat Sheet for a one-page review, and run through timed questions on our practice test platform to see how your domain-by-domain performance compares to the real weighting. Repeated practice sessions on the main practice site are also the fastest way to identify which of the 22 domains still need work before you lock in your test date - details on scheduling are in the exam dates guide.

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