TSSA Gas Technician 1 (G1) key terms

The ratio of a gas's density to that of air at the same conditions. Natural gas is roughly 0.60, so it is lighter than air and rises; propane is about 1.52 and settles in low areas.

The heat released when a unit volume of gas burns completely. Gross value includes latent heat recovered by condensing water vapour; net value excludes it. Ratings and clocking calculations depend on which basis is used.

A number that combines heating value with specific gravity to compare the interchangeability of fuel gases. Gases with similar Wobbe numbers produce similar heat input through the same orifice at the same pressure.

A fuel stored as a liquid under moderate pressure and vaporized for use. It is heavier than air, has a distinct odour, and requires different orifice sizing and ventilation rules than natural gas.

Complete combustion converts all fuel carbon to carbon dioxide with sufficient oxygen. Incomplete combustion leaves carbon monoxide, soot, or aldehydes, signalling too little air, poor mixing, or a blocked flue.

The air supplied beyond the theoretical amount needed for complete combustion, usually expressed as a percentage. Enough excess air keeps carbon monoxide low without excessive dilution of the flue products.

Carbon monoxide is a colourless, odourless product of incomplete combustion that binds to haemoglobin. Technicians measure it in flue gases and ambient air, and must shut down appliances producing unsafe levels or spilling into the space.

A field check of appliance input rate. The technician times a known volume of gas through the meter, then converts the result using the gas heating value to compare measured input with the rating plate.

Selecting the gas jet diameter so the appliance receives its rated input at the available manifold pressure. Orifices are drilled and marked in numbered or letter sizes and must match the fuel and altitude.

The gas pressure measured at the appliance manifold, downstream of the appliance regulator. It is set by the manufacturer and verified with a manometer while the burner operates at full fire.

The outlet pressure a gas regulator settles at when flow stops and the seat closes fully. Lock-up pressure is slightly above flowing pressure; excessive lock-up can overfire burners on startup.

A device that reduces higher supply pressure to a steady lower outlet pressure as demand changes. It uses a diaphragm, spring, and seat, and must be vented and installed in the correct flow direction.

A safety device that restricts or stops gas flow when flow exceeds a set rate, as with a broken line. It is common on propane systems and must be sized so normal appliance demand does not trip it.

A documented test of piping tightness using air, inert gas, or fuel gas at a specified pressure for a set duration, with the gauge observed for drop. Test pressure and duration follow the applicable code.

Choosing pipe and tubing diameters so that pressure loss between the meter or regulator and each appliance stays within code limits at full demand. It accounts for load, length, fittings, and allowable drop.

Displacing air from new or reopened gas piping with fuel gas before ignition is attempted. Purging prevents explosive air-gas mixtures in the pipe and appliance, and must be done to a safe location.

Approved components for gas piping, such as steel pipe, corrugated stainless steel tubing, and copper where permitted, joined with approved fittings. Unlisted materials, excessive thread engagement, and concealed unions are not acceptable.

A dirt pocket installed on the gas line close to the appliance so debris and pipe dope settle out instead of reaching the controls. It is required by code and must be accessible for cleaning.

A listed flexible connector, often corrugated stainless steel or coated brass, used to join the fixed piping to a movable or vibration-prone appliance. It must be sized, protected, and not pass through walls.

The air an appliance needs for burning fuel, distinct from dilution and ventilation air. It may be drawn from the room or ducted from outdoors, and openings must remain unobstructed.

Code terms describing whether a room's volume is large enough to supply combustion, dilution, and ventilation air for the appliances in it. Confined spaces require two permanent openings or dedicated air ducts.

Air supplied to replace air exhausted by fans, dryers, or other equipment so the building does not develop negative pressure. Without it, flue gases can be pulled back down vents.

A condition where indoor pressure is lower than outdoors, often from exhaust fans or unbalanced air systems. It can reverse draft, causing spillage or backdrafting of combustion products into the building.

A device at the appliance flue outlet that limits draft, allows dilution air, and lets flue gases spill rather than pressurize the vent. It is not a substitute for a blocked or undersized chimney.

Flue gases escaping from the draft hood or burner area instead of rising up the vent. Spillage signals a blocked flue, inadequate draft, or depressurization and requires immediate correction.

The negative pressure, measured in inches of water column, that pulls flue gases through the vent. It is checked with a manometer at the appliance outlet or test port and compared with manufacturer values.

The pipe or flue section that carries combustion products from the appliance to the chimney or vent. It must slope upward, be securely joined, and be kept clear of combustible materials at required clearances.

A listed double-wall metal vent with an inner liner and outer casing, used for venting category I gas appliances. It relies on an air space for insulation and must be installed with listed fittings and clearances.

A gas appliance that operates with non-positive vent pressure and a flue gas temperature high enough to avoid condensation in the vent. It is vented with listed venting and checked for draft and spillage.

The minimum distance, specified by listing and code, between heat-producing equipment or venting and combustible materials. Reduced clearance requires listed protection; clearance is not the same as safe working access.

The appearance of a burner flame as a diagnostic. A steady blue flame with a defined inner cone indicates good combustion; yellow tips, lifting, or floating flames suggest air, pressure, or orifice problems.

Primary air mixes with gas before the burner port and shapes the flame; secondary air surrounds the flame to finish combustion. Wrong proportions cause yellowing, lifting, or carbon monoxide.

The component that mixes gas with air and delivers a stable flame at its ports. Burners may be inshot, ribbon, or power types, and must be aligned, clean, and correctly positioned for ignition and flame sensing.

A safety device that generates a small voltage from the heat of a standing pilot flame. That signal holds the gas valve open; if the pilot goes out, the valve closes to prevent unburned gas release.

A device of several thermocouples in series that produces enough voltage to power a millivolt gas valve or control. Output is checked in millivolts under load, with the pilot lit and the valve connected.

A probe or rod that detects flame presence by sensing current through the flame. A dirty, corroded, or poorly positioned sensor causes nuisance lockouts, so the rod and its ground are cleaned and checked first.

The principle behind electronic flame sensing, where the flame conducts current in one direction between the sensor and ground. The control module reads this small direct current to prove flame before opening the valve.

The electronic control that sequences ignition, proves flame, and supervises the gas valve. It enforces trial-for-ignition time and lockout, and its fault codes guide troubleshooting.

An ignition method where a high-voltage spark at the burner lights the gas directly, with flame proved by a sensor. It avoids a standing pilot but requires correct spark gap and clean electrodes.

An ignition method using a silicon nitride or carbide igniter that glows to light the burner. The igniter also often serves as the flame-proving element, so its resistance and warm-up time matter.

A small continuously burning flame that lights the main burner and powers a thermocouple or thermopile safety circuit. Its pilot orifice and flame impingement must be kept clean and correctly adjusted.

A valve, often with an integral regulator and redundant operators, that controls gas flow to the burner. It opens only when the safety circuit and control call for heat, and it must close fully when de-energized.

A temperature- or pressure-actuated safety control that interrupts the burner circuit when a safe limit is exceeded, such as high plenum temperature. It is a safety device and must never be bypassed.

The temperature-responsive control that calls for heat and ends the call when the setpoint is met. It may be low-voltage or millivolt, and its heat anticipator or cycle settings affect comfort and cycling.

The ordered steps an appliance follows: call for heat, safety checks, ignition, flame proving, main burner operation, and shutdown. Understanding the sequence lets a technician locate a fault quickly.

Rules requiring installation, alteration, and replacement work to comply with the gas code and to be authorized by permit and inspection where the authority having jurisdiction requires it. Unpermitted work creates liability and unsafe conditions.

The organization or official responsible for enforcing the gas code and approving equipment, installations, and inspections. Where the code and manufacturer instructions differ, the more stringent requirement generally applies.

The regulatory requirement that gas work be performed by a certified technician holding the appropriate class of licence, and that appliances be certified for the fuel and application. Working beyond your class is a violation.