What does the G3 licence authorize a technician to do in Ontario?

The G3 Gas Technician Level 3 licence issued by TSSA authorizes the holder to install, service, and maintain natural gas appliances in residential buildings. This includes forced-air furnaces, water heaters, dryers, gas ranges, and gas fireplaces. The G3 does not cover commercial or industrial equipment — those require a G2 or G1 licence.

How is the G3 exam structured and what is the passing score?

The TSSA G3 examination is a multiple-choice written test that covers installation codes, appliance service, combustion, venting, and piping. The number of questions and time limit may vary slightly by examination session. A passing score is typically 70% or higher, though TSSA may adjust requirements. Candidates should verify current requirements directly with TSSA before their exam date.

What is the difference between the G3 and G2 gas technician licences?

The G3 is the entry-level gas licence covering residential appliances only. The G2 extends authorization to commercial and industrial gas equipment, higher BTU inputs, and more complex systems such as rooftop units and commercial cooking equipment. Most technicians start with the G3, gain practical experience, and then advance to the G2 examination.

Which code governs G3 gas installations in Ontario?

G3 installations in Ontario are governed primarily by CSA B149.1, the Natural Gas and Propane Installation Code, along with Ontario Regulation 212/01 under the Technical Standards and Safety Act. TSSA also issues Gas Safety Bulletins that supplement the code with additional province-specific requirements. Technicians must stay current with all applicable bulletins.

G3 Gas Technician Level 3 Certification Practice Test PDF (Free Printable 2026)

Download a free G3 Gas Technician Level 3 practice test PDF. Print and study offline for the TSSA Ontario Gas Technician Level 3 certification examination.

G3 - Gas Technician Level 3 CertificationMay 4, 20264 min read

G3 Gas Technician Level 3 Certification – PDF Study Guide

The G3 Gas Technician Level 3 certification is issued by the Technical Standards and Safety Authority (TSSA) in Ontario and authorizes technicians to install, service, and maintain natural gas appliances in residential settings. The G3 is the entry-level gas licence in Ontario and is a prerequisite for the higher-level G2 licence.

This free printable PDF covers all major G3 exam domains: gas appliance installation and service, piping systems, venting systems, combustion fundamentals, applicable safety codes, and customer service documentation. Use it to reinforce classroom learning and identify gaps before your TSSA examination.

Gas Appliance Installation and Service

G3 technicians are authorized to work with residential gas appliances including forced-air furnaces, water heaters, dryers, gas ranges, and gas fireplaces. The exam tests proper installation clearances, gas connection procedures, ignition system types, and service and troubleshooting procedures for each appliance category.

Piping Systems

Questions cover gas pipe sizing using approved tables, acceptable piping materials (black steel, CSST, copper where permitted), pressure testing procedures, and methods for leak detection using approved solutions and instruments. Understanding the difference between high-pressure and low-pressure distribution is essential.

Venting Systems

The exam distinguishes between natural draft, direct vent (sealed combustion), and power vent configurations. You must know vent clearances, termination requirements, and the conditions under which each venting method is appropriate. Negative pressure in tight houses and spillage testing are also tested.

Combustion Fundamentals

A solid understanding of complete versus incomplete combustion, the conditions that produce carbon monoxide (CO), and basic flue gas analysis is required. Stoichiometric ratios, excess air, and CO alarm placement are common exam topics.

Safety Codes and Regulations

G3 candidates must be familiar with the Natural Gas and Propane Installation Code (CSA B149.1), Ontario Regulation 212/01 under the Technical Standards and Safety Act, and TSSA Gas Safety bulletins. Questions test code lookup skills and the ability to apply code requirements to installation scenarios.

G3 vs. G2 Scope of Work

The G3 licence covers residential appliances only. The G2 licence extends authorization to commercial and industrial equipment, larger BTU inputs, and more complex systems. Many technicians earn the G3 first, gain field experience, and then write the G2 examination to expand their scope.

📄Download Free G3 PDF

How to Use This G3 Practice PDF

Work through each section in order, then check your answers against the key. For any question you miss, look up the relevant section of CSA B149.1 or Ontario Regulation 212/01 to understand the rule behind the correct answer. Code literacy is as important as memorization for the TSSA exam.

Pay particular attention to venting and combustion questions — these are the highest-stakes topics because they relate directly to carbon monoxide risk and public safety. TSSA examiners weight these areas heavily, and inspectors in the field will scrutinize your venting work closely.

G3 Exam Day Tips

Bring your approved code books if the exam is open-book — know the index well enough to look up answers quickly under time pressure. Read every scenario question carefully because details like BTU input, pipe material, and appliance location often determine which code clause applies.

If you are unsure between two answers, eliminate clearly wrong options first, then apply the most conservative code interpretation. TSSA exams reward safety-first reasoning. After passing, register your licence with TSSA and confirm any continuing education requirements for renewal.