- How the CSA Blueprint Is Built
- The Seven Domains at a Glance
- Domain 5: Physical Assessment of Cylinder (38%)
- Domain 4: Brackets and High-Pressure Components (18%)
- Domain 1: Preparation for Inspection (13%)
- Domain 6: Original CNG Fuel System Installation (10%)
- Domain 2: Determine Inspection Requirements (9%)
- Domain 3: Pressure Relief Device Inspection (7%)
- Domain 7: Inspection Reporting (5%)
- Exam Format and Registration Mechanics
- Sequencing Your Preparation by Domain
- Frequently Asked Questions
- The CSA Group guide publishes seven weighted objective sections totaling 100%, with the blueprint detail on pages 18-25.
- Physical Assessment of Cylinder carries 38%, more than any other domain and more than Domains 1, 2, 3 and 7 combined.
- The October 2019 PCP-01 guide describes roughly 80 scored multiple-choice questions, possibly 10 unscored evaluation items, in 180 minutes.
- The exam is closed book, and calculators require express sponsor permission.
How the CSA Blueprint Is Built
The Compressed Natural Gas Fuel System Inspector credential is administered by CSA Group, and the official document is titled Personnel Certification Guide: CNG Cylinder and Fuel System Inspector (PCP-01). It is a separate program from AFVi or NGVi certification, so material written for those programs should not be treated as exam content here.
One quirk of the guide is worth knowing before you plan your study. The overview section lists the examination categories without percentages. The detailed blueprint on pages 18-25 is where all seven weights are published. Candidates who read only the overview often walk away with no sense of how heavily each area counts, and that is a costly mistake because the weights are wildly uneven.
A note on currency: the publicly retrievable issuer guide is dated October 2019. It is not a newly issued 2026 blueprint, and the scope and exam source were last checked October 5, 2026. Always confirm the current edition on the CSA registration listing before you commit to a preparation plan. For the broader picture of what the credential is, see What Is CNG-FSI Certification?
The Seven Domains at a Glance
| 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% |
Notice the shape of the distribution. Domains 4 and 5 together account for 56% of the exam. That is the hands-on core of the job: looking at cylinders, brackets and high-pressure hardware and deciding whether they are fit for service. The remaining five domains cover the work that surrounds that core, from getting ready to inspect to documenting what you found.
Domain 5: Physical Assessment of Cylinder (38%)
This is the heart of the exam. More than a third of your score depends on whether you can assess a CNG cylinder the way a working inspector does. If you only have the energy to master one domain, this is the one.
What candidates must understand
Physical assessment is about recognizing condition, damage and acceptance criteria on the cylinder itself, then making a defensible pass-or-reject decision.
- How to distinguish the cylinder types you are likely to encounter and why construction affects what damage matters
- Visual and tactile assessment of the cylinder surface, including the kinds of damage that call for rejection versus monitoring
- Reading cylinder markings and labels to establish identity, service rating and expiry information
- Recognizing environmental, chemical and mechanical damage and judging severity against published criteria
- Knowing when a cylinder must be removed from service rather than returned to the vehicle
Expect scenario-style questions that describe what an inspector sees and ask what the correct disposition is. Memorizing a list of defects is not enough. You need to connect each observation to the acceptance criteria in the standards the exam draws on, and to understand the reasoning, because a question may present a condition in an unfamiliar form.
How to study this domain
Work from the standards and inspection references the CSA guide points to rather than from secondhand summaries. Build your own comparison sheet of damage categories and the decision each one triggers. If you have access to real cylinders or good photographic references, practice describing condition in precise language, since the exam rewards precise recognition. For a quick-reference companion once you have studied the material, the CNG-FSI cheat sheet is useful for last-pass review.
Domain 4: Physical Inspection of Brackets & High-Pressure Components (18%)
The second-largest domain moves from the cylinder to everything that holds it and everything that carries gas at pressure. A cylinder in perfect condition is still a hazard if it is poorly mounted or connected through damaged hardware.
What candidates must understand
This domain tests whether you can inspect mounting hardware and the high-pressure side of the fuel system for condition, security and proper arrangement.
- Bracket and strap condition, fastener security, and signs of movement, wear or corrosion
- Whether the cylinder is correctly supported and protected from chafing and impact
- High-pressure lines, fittings, valves and connections: condition, routing, support and leakage indicators
- Protection of components from road debris, heat sources and mechanical damage
The practical mindset here is that every component is a potential failure point. Questions tend to ask what is wrong with a described installation or what action an inspector should take. Domains 4 and 5 share conceptual ground, so studying them back to back reinforces both.
Domain 1: Preparation for Inspection (13%)
Before you touch a cylinder, there is groundwork. This domain covers the steps and judgment an inspector applies before the physical inspection begins, and it is worth 13% of the exam.
What candidates must understand
Preparation is about safety, readiness and gathering what you need so the inspection is both safe and complete.
- Safe working practices around compressed natural gas, including how the hazards differ from liquid fuels
- Confirming the vehicle or system is in a condition appropriate to inspect
- Having the right tools, references and documentation on hand
- Understanding your responsibilities and limits as an inspector before starting work
These are often the most intuitive questions on the exam for candidates with field experience, which makes Domain 1 a good source of reliable points. It is also where a safety-first answer is nearly always the right one.
Domain 6: Original CNG Fuel System Installation (10%)
This domain concerns the installation of the fuel system as originally fitted, and is worth 10%. Understanding how a system is supposed to be installed gives you the baseline against which you judge what you find in the field.
What candidates must understand
You should know what a compliant original installation looks like so you can spot deviations and unsafe modifications.
- Correct mounting, routing and protection practices for the cylinder and fuel system components
- How installation requirements relate to the applicable codes and standards
- Recognizing when a system departs from the original configuration in a way that affects safety
Candidates who work mostly on inspection sometimes underweight this area because they did not perform the installation. Do not skip it. It supplies the reference picture that makes Domains 4 and 5 easier to reason about.
Domain 2: Determine Inspection Requirements (9%)
Not every system is inspected the same way or on the same schedule. This domain, worth 9%, tests whether you can work out what inspection is actually required in a given situation.
What candidates must understand
The key skill is matching the situation to the requirement, which depends on regulations, standards and the nature of the system in front of you.
- Identifying which standards or regulations govern the inspection for the system at hand
- Determining the scope and timing of required inspections
- Recognizing triggering events, such as damage or incidents, that change what must be done
This domain rewards careful reading. Questions often hinge on a detail in the scenario that changes the applicable requirement. For cost and eligibility context that sits alongside this, see CNG-FSI requirements.
Domain 3: Pressure Relief Device (PRD) Inspection (7%)
The pressure relief device is a small component with a large safety role, and it gets its own domain at 7%. It is a compact area, so focused study pays off quickly.
What candidates must understand
The PRD protects the cylinder from over-pressure or fire exposure, so inspection centers on whether it is present, correct, undamaged and properly installed.
- The purpose of the PRD and how it protects the cylinder
- Visual condition checks and signs that a PRD has been compromised
- Installation, venting and protection considerations
- When a PRD or the cylinder it serves must be taken out of service
Domain 7: Inspection Reporting (5%)
The smallest domain, at 5%, covers documentation. An inspection that is not properly recorded has limited value, and the exam checks that you understand what a complete report requires.
What candidates must understand
Reporting is about accurate, complete and clear records of what was inspected, what was found and what was decided.
- What information an inspection record must contain
- Recording findings and dispositions accurately and unambiguously
- Communicating rejection or removal-from-service decisions appropriately
These are among the more straightforward questions. Give this domain a short, efficient review rather than a long study block, and move your time to the heavily weighted areas.
Exam Format and Registration Mechanics
Knowing the format helps you practice under realistic conditions. Per the October 2019 PCP-01 guide:
- Question style: single-answer multiple choice
- Question count: approximately 80 scored questions, with potentially 10 additional unscored evaluation questions. Treat the count as approximate, not fixed.
- Time: 180 minutes
- Materials: closed book; calculators require express sponsor permission
- Delivery: CSA-authorized computer testing centers through Kryterion, online proctoring, and scheduled paper examinations
- Scoring: criterion-referenced. A numeric cut score was not verified, so see CNG-FSI passing score for what is and is not known.
Older descriptions that mention a 60-question exam or a three-year certification cycle are out of date relative to this guide. Certification lasts five years, and renewal requires reexamination and the applicable fee.
Eligibility and attempts
Formal training is not mandatory. To become certified you need to submit an application, pay the applicable fees, pass the written examination and agree to the ethics and certification terms. Once your application is approved, your examination eligibility lasts six months, with up to three attempts. Second and third attempts require re-examination fees. The current application and exam fee were not verified for this article, so confirm them on the CSA registration listing. For a fuller look at the money side, see CNG-FSI certification cost and for scheduling, CNG-FSI exam dates.
Sequencing Your Preparation by Domain
Because the weights are so lopsided, your calendar should be too. Here is one way to order the work, tied directly to the blueprint. Adjust the pace to your experience; a working inspector may compress the early weeks, while someone new to CNG may need more time on fundamentals.
Foundations: Domains 1, 2 and 7
- Cover safety and preparation (Domain 1) first, since it frames everything else
- Learn how requirements are determined (Domain 2) and what a complete record contains (Domain 7)
- These total 27% and are largely rule-based, so they go quickly
The core: Domain 5
- Spend the longest block here, since it is worth 38%
- Build a damage-to-disposition comparison sheet and test yourself on it
- Practice scenario questions that ask for a pass, reject or remove decision
Hardware and installation: Domains 4, 3 and 6
- Study brackets and high-pressure components (18%), then PRDs (7%)
- Review original installation practice (10%) as the baseline for what you inspect
Integrated review
- Take full-length timed practice sets under the 180-minute limit
- Revisit weak areas in proportion to their weight, not their comfort level
For a broader plan that pairs with this sequence, see the CNG-FSI study guide. If you are weighing whether the effort is manageable, how hard is the CNG-FSI exam gives a candid view of difficulty.
Key Takeaway
Put your hardest study hours into Domain 5 and Domain 4. Together they decide 56% of the exam. Treat Domains 3 and 7 as efficient review blocks rather than major projects, and use timed practice tests to find out where your real gaps are.
Frequently Asked Questions
There are seven weighted sections: Preparation for Inspection (13%), Determine Inspection Requirements (9%), Pressure Relief Device Inspection (7%), Physical Inspection of Brackets & High-Pressure Components (18%), Physical Assessment of Cylinder (38%), Original CNG Fuel System Installation (10%) and Inspection Reporting (5%). They total 100%.
Physical Assessment of Cylinder, at 38%, is the largest by a wide margin. Pair it with Physical Inspection of Brackets & High-Pressure Components at 18% and you have covered more than half of the exam.
The October 2019 PCP-01 guide describes approximately 80 single-answer multiple-choice questions, potentially 10 additional unscored evaluation questions, and 180 minutes. The question count is approximate rather than fixed, and the exam is closed book.
No. Formal training is not mandatory. You do need to apply, pay the applicable fees, pass the written exam and agree to the ethics and certification terms. CSA's optional training course is a separate product with its own cost.
Certification lasts five years, and renewal requires reexamination and the applicable fee. After application approval you have six months of eligibility with up to three attempts, and the second and third attempts require re-examination fees. To see whether the credential pays off for you, read is the CNG-FSI certification worth it and CNG-FSI jobs.