- The trade exam is 85 questions in 180 minutes; you need 60 correct to pass.
- Fuel Systems carries 10 items - the single heaviest domain on the exam.
- You may bring only the 2018 Uniform Mechanical Code and NFPA 54 (2012) as references.
- The trade-only fee is $95; adding the Construction Management Survey brings it to $140.
What the NV-C21 Exam Actually Covers
The Nevada C-21 Refrigeration and Air Conditioning Contractor Trade Exam is administered through PSI Services LLC on behalf of the Nevada State Contractors Board. It's a computer-based, multiple-choice test that becomes available to you only after the Board reviews and approves your contractor application and issues an eligibility notice - you can't just walk in and register on your own timeline.
This is not a general HVAC knowledge quiz. It's a scope-specific trade exam built around the actual licensing classification: refrigeration, air conditioning, heating, and the mechanical systems that support them in Nevada construction. If you're still confirming which credential you're dealing with, our overview at What Is NV-C21? lays out the basics before you dive into prep.
Exam Format, Timing, and the 60-Question Threshold
The trade portion of the exam consists of 85 scored questions, and you're given 180 minutes to complete it. To pass, you need to answer 60 questions correctly. That's the number to build your entire prep strategy around - not a percentage estimate, not a guess, but the literal count published in the PSI bulletin.
One detail that trips people up: PSI may insert between 1 and 10 unscored experimental questions into your exam. These questions don't count toward your score, but they do count against your 180-minute clock, because you have no way of knowing which questions are experimental while you're testing. Budget your pacing as if every question matters - because time-wise, it does.
Key Takeaway
Plan for roughly two minutes per question on average, but don't panic if a handful of items feel oddly unfamiliar - some of those may be unscored experimental questions that won't affect your result.
For a deeper breakdown of exactly how the 60-correct threshold interacts with the 85-question format, see NV-C21 Passing Score 2026: Exactly What You Need to Pass. If you're trying to gauge overall difficulty before committing study hours, How Hard Is the NV-C21 Exam? Complete Difficulty Guide 2026 walks through what makes this particular trade exam demanding.
The 22 Domains: Where the Points Actually Live
The NV-C21 outline is divided into 22 domains, and the official item allocation is published by domain. This is the single most useful piece of information for planning your study time, because the domains are not weighted evenly - some carry a single question, while one carries ten.
| Domain | Approx. Items |
|---|---|
| 1. Piping | 6 |
| 2. Insulation | 1 |
| 3. Hangers and Supports | 3 |
| 4. Sound, Vibration and Seismic Control | 1 |
| 5. Heating and Cooling Principles | 3 |
| 6. Refrigerants and Refrigeration | 7 |
| 7. Load Calculations | 6 |
| 8. Testing, Adjusting and Balancing | 3 |
| 9. Controls | 5 |
| 10. Machine Room | 1 |
| 11. A/C and Heat Pump Equipment | 4 |
| 12. Furnaces and Heaters | 4 |
| 13. Hydronics | 2 |
| 14. Chimneys, Flues and Vents | 5 |
| 15. Combustion Air | 2 |
| 16. Fuel Systems | 10 |
| 17. Ducts | 6 |
| 18. Evaporative Cooling | 2 |
| 19. Chillers | 3 |
| 20. Solar | 4 |
| 21. Ventilation and Exhausts | 3 |
| 22. Safety | 4 |
Fuel Systems is the largest domain on the entire exam at 10 items, followed by Refrigerants and Refrigeration at 7. Together with Piping and Ducts (6 items each) and Load Calculations (6 items), these five domains alone account for close to a third of your total score. If you only have limited time before test day, this is where it needs to go first.
Fuel Systems
As the heaviest-weighted domain, Fuel Systems deserves disproportionate attention relative to smaller domains like Insulation or Sound, Vibration and Seismic Control (1 item each). Candidates should be comfortable with gas piping sizing, appliance connections, venting interaction, and code-driven sizing tables referenced in NFPA 54.
- Know how fuel gas piping sizing interacts with appliance demand and pipe length
- Understand shutoff valve placement and code-required clearances
- Be ready to cross-reference NFPA 54 tables quickly during the exam
Refrigerants and Refrigeration
At 7 items, this domain covers refrigerant properties, cycle operation, recovery and handling, and the practical mechanics of refrigeration equipment used in commercial and residential systems.
- Understand pressure-temperature relationships for common refrigerants
- Know recovery, recycling, and handling procedure basics
- Be familiar with compressor and evaporator troubleshooting scenarios
For the full narrative walkthrough of all 22 content areas - including the smaller-weight domains that still show up on every exam form - see NV-C21 Exam Domains 2026: Complete Guide to All 22 Content Areas.
Registration, Fees, and Eligibility Mechanics
Before you ever sit for the trade exam, the Nevada State Contractors Board has to approve your application. That process includes experience verification, a financial and background review, and confirmation of a license bond and applicable insurance. None of this happens overnight, so build it into your timeline well before you start memorizing gas piping tables.
Eligibility for the trade qualifier ordinarily requires four years of journeyman, foreman, supervising-employee, or contractor experience within the preceding fifteen years. Approved education can substitute for up to three of those four years, which matters if you're coming from a formal trade program rather than pure field time. The full mechanics of qualifying - including how documentation is evaluated - are covered in NV-C21 Requirements 2026: Eligibility, Prerequisites & How to Qualify.
Note that the Construction Management Survey has its own separate passing standard from the trade exam - passing one does not automatically satisfy the other. Plan to prepare for both if the survey isn't waived for you.
What You Can (and Cannot) Bring Into the Exam
The NV-C21 trade exam is open book, but "open book" here means something very specific and narrow. You are permitted to bring exactly two references: the 2018 Uniform Mechanical Code and the NFPA 54 National Fuel Gas Code (2012 edition). Nothing else.
Within those two books, you're allowed to pre-highlight, underline, and add permanent tabs before test day. What you cannot do is bring handwritten notes, temporary tabs, sticky flags you plan to move around, or any loose supplemental material tucked into the pages. PSI is strict about this - testing center staff will check your books before you sit down.
- Allowed: permanent tabs, pre-existing highlighting, underlining done in advance
- Not allowed: handwritten margin notes, removable tabs, inserted loose papers
- Also allowed: a silent, non-programmable calculator that meets PSI's restrictions
Key Takeaway
Spend prep time learning to navigate the 2018 UMC and NFPA 54 (2012) by index and table number, not just by content. Speed of lookup matters as much as knowing the material exists.
Because your only references are code books rather than a formula sheet, your exam-day success depends heavily on knowing exactly where to find tables under time pressure. A condensed reference like the NV-C21 Cheat Sheet 2026: One-Page Review of Must-Know Facts can help you drill the lookup patterns before you're relying on the real code books under a countdown clock.
A Domain-Weighted Study Timeline
Generic study advice - spaced repetition, timed practice blocks, whatever method you prefer - only helps if it's pointed at the right material. For NV-C21, that means letting the domain weightings from the outline dictate your calendar, not treating all 22 domains as equally important.
Highest-weight domains
- Fuel Systems (10 items) - gas piping sizing and NFPA 54 tables
- Refrigerants and Refrigeration (7 items) - cycle operation and recovery
Mid-weight structural and airflow domains
- Piping, Ducts, and Load Calculations (6 items each)
- Controls and Chimneys/Flues/Vents (5 items each)
Equipment-specific domains
- A/C and Heat Pump Equipment, Furnaces and Heaters, Solar, Safety (4 items each)
- Hangers and Supports, Testing/Adjusting/Balancing, Heating and Cooling Principles, Chillers, Ventilation and Exhausts (3 items each)
Lower-weight domains and full review
- Hydronics, Combustion Air, Evaporative Cooling (2 items each)
- Insulation, Sound/Vibration/Seismic Control, Machine Room (1 item each)
- Full timed practice run with only your approved code references
Notice that the last week's domains - Insulation, Sound/Vibration/Seismic Control, and Machine Room - total just 3 items combined. That's intentional: don't burn a full week's worth of energy on material worth almost nothing relative to Fuel Systems or Refrigerants and Refrigeration.
If You Don't Pass the First Time
Nevada's retake rules are worth knowing before test day, not after. If you don't reach 60 correct answers, you must wait two weeks before retaking the exam. That's a firm minimum, so don't assume you can rebook the next morning out of frustration.
The bigger risk is the three-attempt limit. If you fail the trade exam three times, your application is voided outright, and you have to wait 30 days before you can reapply from scratch - meaning a new application, not just a new exam slot. That's a meaningful setback in both time and paperwork, which is exactly why domain-weighted prep matters more than cramming broadly.
If you're weighing whether the licensing effort is worth it relative to the work you'll be doing afterward, Is the NV-C21 Certification Worth It? Complete ROI Analysis 2026 covers that angle in more depth. And once you've got the format and domains internalized, running full-length timed sets on our practice test platform is the most direct way to simulate the real 85-question, 180-minute pressure before you walk into the testing center.
Frequently Asked Questions
The trade exam has 85 scored questions, and you need 60 correct answers to pass. PSI may add up to 10 additional unscored experimental questions that count against your time but not your score.
Only the 2018 Uniform Mechanical Code and the NFPA 54 National Fuel Gas Code (2012 edition). You can pre-highlight, underline, and add permanent tabs, but handwritten notes, temporary tabs, and loose inserted material are not permitted.
Fuel Systems, at 10 items, is the largest domain on the exam. Refrigerants and Refrigeration follows at 7 items. Together with Piping, Ducts, and Load Calculations, these domains cover a large share of the 85 questions.
The trade portion alone is $95. If you also need the Construction Management Survey business-and-law package, the combined fee is $140. Separately, the Nevada contractor application fee is $300.
You must wait two weeks between attempts. After a third failed attempt, your application is voided and you must wait 30 days before reapplying with a new application.