- What This Cheat Sheet Covers (and What It Doesn't)
- Exam Format at a Glance
- The Seven Domains and Their Weights
- Domain 5: Physical Assessment of Cylinder (38%)
- Domain 4: Brackets and High-Pressure Components (18%)
- The Smaller Domains Worth Real Points
- Registration, Eligibility and Renewal Mechanics
- Training Course vs. Certification Exam: Don't Mix the Numbers
- A Weight-Driven Review Schedule
- Where the Credential Gets Used
- Frequently Asked Questions
- Physical Assessment of Cylinder carries 38% of the exam, more than any two other domains combined except Domain 4.
- Expect roughly 80 single-answer multiple-choice questions, possibly 10 unscored extras, in a 180-minute closed-book sitting.
- Eligibility runs six months from application approval, with up to three attempts; retakes require re-examination fees.
- Certification lasts five years and renewal requires reexamination, so ignore older three-year-renewal descriptions.
What This Cheat Sheet Covers (and What It Doesn't)
This page condenses the facts a Compressed Natural Gas Fuel System Inspector candidate should be able to recall without notes. The credential in question is the CSA Group program whose official guide is titled Personnel Certification Guide: CNG Cylinder and Fuel System Inspector (PCP-01). It is a separate program from AFVi or NGVi certification, so do not blend materials from those paths into your review.
One honest caveat up front: the publicly retrievable issuer guide is the October 2019 edition of PCP-01, not a newly issued 2026 blueprint. Everything below was checked against that document, especially the detailed blueprint on pages 18-25. A numeric cut score and the current application and exam fees were not verified, so this sheet will not guess at them. For a deeper walk through the program itself, see What Is CNG-FSI? and the full CNG-FSI Study Guide.
Exam Format at a Glance
| Item | What the Guide Says |
|---|---|
| Question type | Single-answer multiple choice |
| Question count | Approximately 80 scored questions; potentially about 10 additional unscored evaluation questions |
| Time allowed | 180 minutes |
| Reference materials | Closed book |
| Calculators | Only with express sponsor permission |
| Delivery options | CSA-authorized computer testing centers (through Kryterion), online proctoring, and scheduled paper examinations |
| Scoring approach | Criterion-referenced; numeric cut score not verified |
Because the exam is closed book and calculators are not a given, arithmetic and unit reasoning need to be comfortable by hand. Confirm calculator rules with CSA when you schedule rather than assuming. For a candid look at how this format feels in practice, read How Hard Is the CNG-FSI Exam?
The Seven Domains and Their Weights
The guide's overview lists the categories without percentages, but the detailed blueprint publishes all seven weights, and they total 100%.
| Domain | Name | Weight |
|---|---|---|
| 1 | Preparation for Inspection | 13% |
| 2 | Determine Inspection Requirements | 9% |
| 3 | Pressure Relief Device (PRD) Inspection | 7% |
| 4 | Physical Inspection of Brackets & High-Pressure Components | 18% |
| 5 | Physical Assessment of Cylinder | 38% |
| 6 | Original CNG Fuel System Installation | 10% |
| 7 | Inspection Reporting | 5% |
Two domains, 4 and 5, account for 56% of the exam. If you have limited time, that is where the arithmetic points you. The full breakdown lives in the CNG-FSI Exam Domains guide.
Domain 5: Physical Assessment of Cylinder (38%)
Physical Assessment of Cylinder
This is the heart of the credential. Questions here test whether you can look at a cylinder and make a defensible accept-or-reject judgment against the applicable criteria.
- Recognize the categories of visible damage and degradation a cylinder can show, and know which findings call for removal from service.
- Understand how cylinder construction type affects what you look for and how damage is evaluated.
- Know how to read cylinder labels, markings and documentation, and what a missing or illegible label means for the inspection outcome.
- Distinguish conditions that are merely cosmetic from conditions that compromise structural integrity.
- Apply the guide's acceptance and rejection criteria consistently rather than relying on general mechanical intuition.
Expect scenario-style stems in this domain: a described condition, then a single best answer about the correct disposition. The skill being tested is judgment anchored to published criteria, so memorize the criteria themselves instead of trying to reason from first principles. Candidates who treat this as a mechanical-trades quiz tend to lose points on the exact wording of criteria.
Key Takeaway
With 38% of the exam resting on one domain, a weak showing here is very hard to offset elsewhere. Make Domain 5 your first and last review block, and revisit it after every other domain.
Domain 4: Brackets and High-Pressure Components (18%)
Physical Inspection of Brackets & High-Pressure Components
The second-largest domain covers everything that holds the cylinder in place and carries gas at pressure.
- Mounting brackets, straps and attachment hardware: condition, security, and signs of wear or movement.
- High-pressure lines, fittings and connections: leaks, chafing, corrosion, improper routing and inadequate support.
- Valves and other pressure-bearing components: what a sound installation looks like versus a deficient one.
- Protection from road hazards, heat and abrasion where components are routed or mounted.
This domain rewards a systematic walk-around mindset. The questions often hinge on spotting the single deficiency in an otherwise acceptable description. Practice reading each scenario for what is wrong, not just what is present.
The Smaller Domains Worth Real Points
The remaining five domains total 44%, which is far too much to skip. They are also where candidates with field experience sometimes get surprised, because they test procedure and documentation rather than hands-on feel.
Domain 1: Preparation for Inspection (13%)
Think safety and readiness before a hand touches the vehicle: confirming the vehicle is safe to inspect, gathering the right records and tools, and understanding the conditions under which an inspection should or should not proceed. This is the third-largest domain and is easy to underweight.
Domain 2: Determine Inspection Requirements (9%)
This domain is about deciding what inspection applies. Know how to determine which requirements govern a given cylinder or installation and what triggers an inspection. Expect questions that ask you to match a situation to the correct inspection requirement.
Domain 3: Pressure Relief Device (PRD) Inspection (7%)
PRDs are safety-critical, and the guide gives them their own domain. Understand what a PRD does, how it is installed, and what conditions make one unacceptable. Seven percent is roughly five or six questions on an 80-item exam, so treat it as a compact, memorizable block.
Domain 6: Original CNG Fuel System Installation (10%)
Here the focus shifts to whether the original installation was done correctly. Know what a compliant installation looks like so you can recognize non-conforming work during an inspection. Several questions will connect back to Domain 4 hardware, so study them together.
Domain 7: Inspection Reporting (5%)
The smallest domain, but also the most predictable. Know what a complete inspection record contains and how findings and dispositions are documented. Because it is narrow and procedural, this is among the cheapest points available.
Registration, Eligibility and Renewal Mechanics
- Formal training: not mandatory.
- What is required: an application, applicable fees, passing the written examination, and agreement to the ethics and certification terms.
- Exam eligibility window: six months from application approval.
- Attempts: up to three within that eligibility period; second and third attempts require re-examination fees.
- Certification term: five years.
- Renewal: requires reexamination and the applicable fee.
- Passing standard: criterion-referenced. A numeric cut score was not verified, so do not trust any single "pass mark" you see quoted elsewhere.
The six-month clock is the detail candidates most often mismanage. Apply when you are close to ready, not when you are merely curious, because the window starts at approval and your attempts live inside it. See CNG-FSI Requirements for eligibility detail, CNG-FSI Exam Dates for scheduling, and CNG-FSI Passing Score for what is and isn't known about scoring. If you are weighing cost, the certification cost breakdown explains why a single fee figure can't be quoted with confidence here.
Training Course vs. Certification Exam: Don't Mix the Numbers
CSA also sells a separate, optional preparation product: CNG Container and Fuel System Inspector Training. Its listing describes a self-paced option at USD 730, four course hours and 90-day access. Those are training terms.
| Figure | Belongs To | Is It the Exam? |
|---|---|---|
| USD 730 | Optional self-paced training course | No, not the exam fee |
| Four course hours | Training course length | No, not the exam duration |
| 90-day access | Training course access period | No, unrelated to the six-month exam eligibility |
| 180 minutes | Written examination time limit | Yes |
Mixing these up is an easy mistake and leads to bad planning, such as budgeting only the course price or assuming the exam is a four-hour event. For help deciding whether the course is worth adding, read about CNG-FSI training.
A Weight-Driven Review Schedule
This is the one place to be methodical. Sequence your weeks by domain weight and by how domains reinforce each other, not by the order they appear in the guide.
Scope, Requirements and Reporting
- Domain 2 (inspection requirements) and Domain 7 (reporting): small, procedural, quick wins.
- Domain 3 (PRD inspection) as a compact safety block.
Hardware and Installation
- Domain 4 (brackets and high-pressure components) and Domain 6 (original installation), studied together because they describe the same hardware from two angles.
Cylinder Criteria
- Domain 5 (38%) in depth: damage categories, acceptance and rejection criteria, markings and documentation.
- Pair with Domain 1 (preparation) so safe-inspection steps stay connected to the cylinder work.
Timed Practice and Gap Repair
- Full-length timed sets against the 180-minute limit, closed book.
- Return to Domain 5 for every missed cylinder question and re-read the underlying criteria.
If your experience is mostly installation work, shift extra hours to Domain 5 and Domain 7. If you come from a cylinder-inspection background, the reverse is often true: installation (Domain 6) and requirements (Domain 2) are the usual soft spots. Use timed practice tests to find your actual weak domain rather than guessing. A broader look at pacing and resources is in the study guide.
Where the Credential Gets Used
An inspector credential of this kind is relevant wherever compressed natural gas vehicles are built, converted, serviced or kept in service. That generally means fleet operators running CNG vehicles, vehicle conversion and upfitting shops, service and inspection facilities, and organizations responsible for the safety of vehicles with onboard natural gas fuel storage. The credential signals that you can assess cylinders and fuel system components against recognized criteria and document the result.
Specific employer lists, hiring volumes and pay figures were not verified for this guide, so none are quoted here. For discussion of the career side, see CNG-FSI jobs, the salary guide, and the ROI analysis.
Frequently Asked Questions
The October 2019 PCP-01 guide describes approximately 80 single-answer multiple-choice questions, with potentially about 10 additional unscored evaluation questions. Treat the count as approximate rather than fixed, and note that older 60-question descriptions are outdated.
Domain 5, Physical Assessment of Cylinder, at 38%. Domain 4, Physical Inspection of Brackets & High-Pressure Components, is next at 18%. Together they make up 56% of the blueprint.
No. Formal training is not mandatory. You must submit an application, pay applicable fees, pass the written examination and agree to the ethics and certification terms. CSA's optional training course is separate and priced independently of the exam.
Eligibility lasts six months from application approval, with up to three attempts. The second and third attempts require re-examination fees, so a first-attempt pass saves money as well as time.
Five years. Renewal requires reexamination and the applicable fee. Descriptions of a three-year renewal cycle reflect legacy information and should not be used for planning.