Level 1, Unit 5, Section 2 – Air-Fuel & Oxy-Fuel

Unit 5 — Pressure Testing, Tubing, and Piping

Section 2 — Air-Fuel & Oxy-Fuel

Section 2 Overview

This section covers both air-fuel and oxy-fuel cutting and welding systems: equipment assembly and connection, flame adjustment and operation, and the safety practices required by Ontario regulations and industry standards.

Air-Fuel Oxy-Fuel Cutting & Brazing 313A / 313D

2.0.1 — General Learning Outcomes

By completing Section 2, apprentices will be able to:

Identify air-fuel outfit components, assemble the outfit correctly, and light the torch safely following the prescribed sequence.
Adjust air-fuel torch pressure and flame type, perform silver-brazing and soldering operations, and execute a controlled shutdown.
Recognize PPE requirements for air-fuel work, describe backfire and flashback causes, and apply fire hazard reduction practices on a job site.
Identify oxy-fuel outfit components, connect regulators and hoses using correct thread direction, and assemble the outfit with flashback arresters and reverse-flow check valves.
Adjust oxy-fuel regulator pressures, distinguish neutral, oxidizing, and carbonizing flames, and perform steel-cutting operations using the correct five-step technique.
Describe the causes and emergency response to backfire and flashback, clean and inspect cutting tips, perform a soap-solution leak check, and explain ventilation requirements for oxy-fuel work.

2.0.2 — Section 2 — Lessons at a Glance

Lesson 1.3

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Air-Fuel Assembly & Lighting

Outfit components, assembly sequence, hose colour coding, and torch lighting procedure.

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Lesson 1.4

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Air-Fuel Operation

Pressure and flame adjustment, silver-brazing and soldering procedures, and safe shutdown.

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Lesson 1.5

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Air-Fuel Safety

PPE selection, backfire and flashback causes, ventilation requirements, and fire prevention.

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Lesson 2.4

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Oxy-Fuel Assembly & Lighting

Regulator selection, hose thread direction, flashback arrester installation, and outfit assembly.

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Lesson 2.5

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Oxy-Fuel Operation

Regulator adjustment, neutral and oxidizing flame identification, and steel-cutting technique.

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Lesson 2.6

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Oxy-Fuel Safety

Flashback and reverse-flow protection, tip cleaning, leak checking, and combustion byproducts.

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2.0.3 — Key Terms for This Section

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Flashback

Flame travels back through the hose into the regulator or cylinder. Caused by reverse gas flow, blocked tip, or improper pressures. Requires immediate shutdown and equipment inspection.

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Flashback Arrester

A safety device fitted at the torch inlet or regulator outlet that contains a sintered metal disc to quench a flashback flame and a check valve to stop reverse flow. Required on all oxy-fuel outfits.

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Neutral Flame

An oxy-fuel flame with a balanced oxygen-to-fuel ratio. It produces a bright inner cone with no feathery carbonizing fringe, and is the standard setting for most cutting and brazing operations.

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Reverse-Flow Check Valve

A one-way valve installed in each hose line that prevents gas from flowing backward into the regulator or opposite cylinder. Provides the first line of defence against cross-contamination.

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Backfire

A momentary flashback that extinguishes at the tip — distinguished from a full flashback by a loud pop and self-extinguishing flame. Usually caused by tip contact with the work or excessive tip heat.

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BLEVE

Boiling Liquid Expanding Vapour Explosion — catastrophic cylinder failure caused by external fire heating a pressurized cylinder. Prevented by proper cylinder storage, handling, and never exposing cylinders to flame or heat.

2.0.4 — Why Air-Fuel & Oxy-Fuel Matter

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Scope of Use in HVAC/R

Air-fuel and oxy-fuel torches are used daily in HVAC/R work for copper tube brazing, silver soldering, pipe cutting, and occasional welding on steel components. Mistakes during assembly or operation can result in hose fires, flashback, cylinder explosion, or prolonged exposure to toxic combustion gases including CO, CO₂, and nitrogen oxides.

Ontario's TSSA — Fuels Safety Branch and the Ontario Fire Code govern hot-work permits, storage of fuel cylinders, and minimum ventilation requirements on job sites. Section 2 content aligns with the 313A (Commercial/Industrial) and 313D (Residential) apprenticeship curricula and prepares apprentices for safe daily practice under their licensed contractor.