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.
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.
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.
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.
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.
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.
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.
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.
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.