Gas Appliance Fundamentals and Safety
Natural gas and propane properties, gas valves, thermocouples, flame sensors, pressure regulators, draft hoods, and gas leak detection.
- Compare natural gas and propane fuel properties
- Explain thermocouple and flame sensor operation
- Describe gas pressure regulator function and adjustment
- Identify gas leak detection methods and safety procedures
- Explain draft hood and flue safety device requirements
Lesson 1
Natural Gas and Propane Properties
Residential Gas Fuels in Canada
The type of gas commonly used in residential gas appliances in Canada is natural gas (methane). Natural gas is supplied through municipal distribution pipelines at a typical delivery pressure of 7 inches of water column (7" WC) to the appliance. It is lighter than air with a specific gravity of approximately 0.60, which means it rises and disperses when it leaks.
Propane (LP gas) is the common alternative in rural areas without natural gas pipelines. Propane is heavier than air with a specific gravity of approximately 1.52, meaning it sinks and pools in low-lying areas when it leaks. This makes propane leaks particularly dangerous in basements and crawl spaces.
Natural Gas
Specific gravity: 0.60 (lighter than air)
Supply pressure: 7" WC typical
BTU per cubic foot: ~1,000
Leak behavior: Rises and disperses
Propane (LP Gas)
Specific gravity: 1.52 (heavier than air)
Supply pressure: 11" WC typical
BTU per cubic foot: ~2,500
Leak behavior: Sinks and pools in low areas
Orifice Differences
When converting an appliance from natural gas to propane (or vice versa), the burner orifices must be changed. Propane orifices are smaller because propane has a higher BTU content per cubic foot. Using natural gas orifices with propane results in dangerously oversized flames, while using propane orifices with natural gas produces weak, insufficient flames.
Conversion Kits Are Mandatory
Never operate a gas appliance on a fuel type it is not configured for. A proper conversion kit includes correct orifices, a pressure regulator spring, and updated rating plate. Incorrect fuel type can cause carbon monoxide poisoning, fire, or explosion.
Natural gas is the standard residential fuel in Canada, delivered at 7" WC. It is lighter than air and rises when leaked. Propane is heavier than air and pools in low areas, making leaks more dangerous. Always use the correct orifice size for the fuel type.