Know what you're walking into
Most G3 failures aren't about intelligence. They're about walking into a code-navigation exam having only memorized facts. Start by understanding the test itself.
- Format
- Multiple choice, four options, one best answer. Written in person at a Prometric test centre. The sitting is up to 3.5 hours.
- Pass mark
- 75% — the same for all TSSA Fuels exams. There is no curve and no partial credit.
- Open book
- A hard-copy CSA code book only — unmarked and unaltered. No notes, no highlighting, no tabs with writing.
- No prerequisites
- Any uncertified individual may challenge the G3 written exam with no course and no experience requirement.
- After the exam
- Passing is step one. You must then complete a practical skills assessment arranged with a TSSA Training and Certification Advisor within one year.
- Retakes
- Three failed attempts on the same exam means completing an accredited training program before you can write again.
TSSA does not publish exact question counts or pass rates. Confirm the current exam fee in the TSSA Client Portal when you apply.
Your code book is the real exam
Open book does not mean easy. It means the exam is, in large part, a code-navigation speed test. A good share of G3 questions give you a scenario — an appliance input, a piping run, a venting layout — and the answer is a number or rule buried in a clause or table. The candidates who pass are the ones who can find the right clause in under a minute, not the ones who tried to memorize the book.
So the single most important study habit is this: practise with your own clean code book from day one. Never study from a marked-up copy. Learn the table of contents the way you'd learn a map, and learn the index as your fallback. Every time you learn a rule, physically turn to the clause it lives in. Do this a hundred times and your hands will know where things are before your brain does.
Confirm the current permitted-reference rules in the TSSA Certification Examination Preparation Guide before exam day. Rules about what's allowed change, and a book that violates them can be taken away at the door.
An 8-week study plan that actually works
The G3 curriculum is nine units. Eight weeks at 60 to 90 minutes a day is enough — if you work through the units in the right order and drill the code as you go. This is the same structure used in our G3 & G2 study guide.
- Weeks 1–2: Safety, tools, and the easy marks — Units 1–2 (safety and WHMIS, tools and fasteners). Bank the straightforward material early and build the daily habit.
- Weeks 3–4: The heavyweight units — Units 3–4 (gas properties and combustion, codes and regulations). These two units drive more questions than any others. Do a code-check drill for every rule you meet.
- Weeks 5–6: Electricity, manuals, customer relations — Units 5–7. Electricity basics trip up candidates who skip the math; work the practice problems with a calculator in hand.
- Weeks 7: Piping and appliances — Units 8–9 (piping and tubing, gas appliances). Sizing questions live here — slow down and learn the tables.
- Week 8: Mock exams and review — two full timed mock exams, then spend your review time only on the questions you got wrong. Do not re-read units you already know.
Practice questions the right way
Practice questions only work if the answers are explained, not just marked right or wrong. When you miss one, you need to know which clause or concept you misunderstood — otherwise you'll miss the same question dressed differently on exam day. Keep a running list of your misses and re-attempt them a week later. If you miss the same concept twice, that's your study priority, not the chapters you already ace.
Pay special attention to questions flagged as traps: the wrong answers on a well-built exam look right on purpose. Learn why the distractor is wrong and you'll be faster at eliminating options under time pressure. The study guide's Exam Trap boxes exist for exactly this.
The traps that cost people the exam
Watch out for old-code practice material
In June 2026 Ontario moved to the 2025 editions of the B149 series, and clause numbers were renumbered versus the 2020 editions. A huge amount of free practice material online is still keyed to the old codes. A question is not automatically wrong because its clause reference is stale — but if you train yourself to look things up by old clause numbers, you'll be slow and lost with the current book. Study from material written for CSA B149.1:25 and B149.2:25, and always verify figures against your own current code books.
Three more traps, all avoidable:
- "Which of the following is NOT…" — read the last line of the question first, every time. A missed NOT turns a question you know into a wrong answer.
- Unit conversions. Imperial/metric mix-ups are the cheapest marks to lose. Write the conversion factor down before you touch the calculator.
- Memorized answers to old questions. The exam tests understanding, not recall. If you can't explain why an answer is right, you don't know it yet.
Two timed mocks before you book your seat
Do not book your Prometric sitting until you have written at least two full-length mock exams under real conditions: timed, code book open, phone away, no pausing. Score them honestly. If you're consistently at or above 80%, book the exam. If you're hovering near 75%, you have no margin for a bad day — keep studying.
Use the mocks to calibrate your pacing. The three-pass method works well for this exam:
- Pass one: answer everything you know cold, fast. Don't open the code book.
- Pass two: work the questions that need a code lookup or a calculation.
- Pass three: wrestle with the hard ones. Answer every question — an unanswered question can never earn a mark.
Questions
Can I write the TSSA G3 exam without taking a course?
Yes. There are no prerequisites to challenge the TSSA G3 written exam. After passing, you must complete a practical skills assessment arranged with a TSSA Training and Certification Advisor within one year.
What is the pass mark for the G3 exam?
The pass mark is 75%. This applies to all TSSA Fuels exams.
Can I bring my code book into the G3 exam?
Yes, a hard-copy CSA code book is permitted, but it must be unmarked and unaltered — no notes, highlighting, or tabs with writing. Confirm the current rules in the TSSA Certification Examination Preparation Guide before exam day.
Which code edition should I study for the G3 exam?
Study CSA B149.1:25 and B149.2:25 as adopted in Ontario by the 2026 Code Adoption Documents (in force June 2026). Clause numbers were renumbered versus the 2020 editions, so older practice material can point you to the wrong place.
Study the way the exam tests.
Our 133-page G3 & G2 guide follows this exact plan: all 24 units, 375+ practice questions with fully explained answers, code navigation drills, and two full-length timed mock exams. Written for B149.1:25 and B149.2:25.