403A Red Seal — Gas Fitter (Class A)

About the 403A Red Seal Exam — Gas Fitter (Class A)

The 403A Gasfitter (Class A) Red Seal exam is Canada's national certification for gas fitters working on all types and pressures of natural gas and propane systems. Class A certification covers residential, commercial, and industrial gas installations including high-pressure supply, appliance commissioning, venting design, and combustion analysis.

The exam consists of approximately 100 multiple-choice questions based on the 2023 Red Seal Occupational Standard (RSOS) and aligned with CSA B149.1 Natural Gas and Propane Installation Code, with a passing score of 70%. Exam time is 3 hours.

Topic Breakdown (2023 RSOS)

• Appliances & Combustion Equipment (~22%) — Furnaces, boilers, water heaters, unit heaters, infrared heaters. Burner adjustment, heat exchanger inspection, ignition systems, and commissioning.
• Gas Supply Systems (~18%) — Meter sets, regulators (service, line, appliance), pressure testing, odourant, and first/second stage regulation.
• Piping Systems (~16%) — Pipe sizing using pressure drop tables, pipe materials (black steel, CSST, copper, PE), fittings, supports, and leak detection.
• Venting Systems (~16%) — Category I–IV venting, natural/induced/direct vent, common vent sizing, termination clearances.
• Combustion Theory & Air (~14%) — Stoichiometric combustion, excess air, CO/CO₂ analysis, combustion air requirements (0.08 m²/kW).
• Safety, Codes & Regulations (~14%) — CSA B149.1, provincial requirements, permits, pressure testing, gas leak response, purging.

How to Use This Practice Tool

This free tool includes 100 questions covering all 403A topic blocks with full explanations citing the relevant CSA B149.1 section for every answer. Use Topic Filter to drill your weakest areas. Run the Mock Exam to simulate the real 100-question timed format.

Related reading: How to Pass the 403A Red Seal Exam | Gas Fitter Salary Guide | Gas Fitter Career Guide Canada