Glossary – Block A: Fuel Gas

When the pressure is relative to a perfect vacuum, it is referred to as "absolute pressure," which equals gauge pressure plus atmospheric pressure. (Section A-4.1)

A gas-fired refrigerator that uses heat from a gas flame to drive a chemical process involving ammonia, water, and hydrogen to produce cooling—without a compressor. (Section A-1.2)

(For combustion); The air required by a gas appliance to support proper combustion, which may need to come from outside depending on appliance type and building design. (Section A-2.2)

A device used to measure electric current in a circuit. It shows the amount of current flowing through the circuit in units called amperes (amps). (Section A-4.3)

Instruments that show measured values using a scale and pointer; the pointer moves in a direct and continuous way to show how much of something is being measured. (Section A-4.3)

A device automatically selects the best measurement range for what you're testing; this makes it easier because you don't have to set the range yourself—it adjusts on its own to give you the most accurate reading. (Section A-4.3)

The Canadian standard that governs the installation of natural gas and propane appliances and equipment. It's a critical document for all gas-related work. (Section A-2.2)

The reverse flow of gas in the flues of fuel-fired appliances that results in the intrusion of combustion by-products into the living space. (Section A-3.4)

A type of pressure gauge used specifically to measure atmospheric pressure. The units of measure used are inches of mercury (in. Hg). (Section A-4.1)

A device used in heating systems to help control the airflow going in and out of the chimney. It automatically adjusts to make sure the right amount of air is flowing through the system, which helps the appliance burn fuel more efficiently. This keeps the system working properly and prevents problems like too much smoke or wasted energy. (Section A-3.3)

A "black-body source" is an object that is perfect at absorbing and giving off heat energy. It doesn't reflect any light; instead, it takes in all the energy that hits it and then emits the maximum amount of energy possible for its temperature. When we talk about "emissivity," we're comparing how much energy a real object emits compared to this perfect black body. So, if a material has high emissivity, it's very good at emitting heat energy, like the black body. If it has low emissivity, it's not as good at emitting heat. (Section A-4.2)

A type of gauge that measures the pressure of liquids and gases; it uses an elastic tube that bends under pressure, moving a pointer to indicate the pressure on a scale. This device can measure pressures up to 100,000 psi (70,000 newtons per square cm). (Section A-4.1)

A unit of energy used to measure the heat content of fuel. (Section A-3.2)

The physical boundary between the conditioned and unconditioned parts of a building, which includes the foundation, roof, walls, doors, windows, and insulation, and controls the flow of air, heat, and moisture. (Section A-3.4)

A framework made up of different subsystems, including occupants, the building envelope, outside environment, and mechanical/electrical equipment, that work together to manage air, heat, and moisture flow. (Section A-3.4)

A specialized oval-shaped vent system designed for use with natural draft appliances like recessed wall furnaces, allowing installation within wall cavities. (Section A-1.2)

A safety device that detects dangerous levels of carbon monoxide gas and may activate a shut-off mechanism on gas appliances. (Section A-1.2)

(CSA B149.1); The different types of natural gas appliances classified based on their efficiency and the pressure of their venting system. The classification helps determine how the appliance operates and how the combustion gases are vented. There are four main categories: Category I, Category II, Category III, and Category IV, with each category indicating a specific range of efficiency and venting pressure. (Section A-3.3)

Groups that check if products are made and work safely and correctly. They put special labels on products to show they meet safety rules. Accredited certification organizations apply a special certification symbol. (Section A-1.3)

Also called a gas leak detector, this device is used to detect and measure the presence of flammable gases in the air, it helps to identify potentially hazardous levels of gases that could ignite or pose health risks. (Section A-4.4)

Any material that can ignite and burn. The code contains specific clearance requirements to prevent fire hazards. (Section A-2.2)

The rapid oxidation of fuel, accompanied by heat or heat and light. Combustion is essential for gas appliances to operate properly. (Section A-3.1)

The air required for the combustion process, expressed as an air/gas ratio (10:1 for natural gas, 25:1 for propane). (Section A-3.2)

The ideal burning process where there is enough oxygen to burn all the fuel completely, producing only carbon dioxide (CO₂), water vapor (H₂O), and heat as byproducts. (Section A-3.1)

A type of gauge that can measure pressures both above and below atmospheric pressure. (Section A-4.1)

A type of pipe made of two pipes, one inside the other. The outer pipe carries air, while the inner pipe carries the fuel or exhaust, helping to safely vent gases while bringing in fresh air for combustion. (Section A-1.1)

A common type of analogue thermometer available in two general types: stem and flexible capillary. They typically use a bimetallic temperature-sensing element in the stem, where temperature changes cause the element to bend or twist, moving the pointer via a mechanical linkage. (Section A-4.2)

The difference in pressure between two contained working fluids. (Section A-4.1)

A type of gauge with two inlet ports, each connected to one of the volumes whose pressure is to be monitored; this gauge can be used to monitor air flow, check the amount of filter clogging, and test equipment operation; it performs the mathematical operation of subtraction through mechanical means. (Section A-4.1)

Instruments that use electronics to read and display exact numerical data or measurements using LEDs or LCDs as numbers on a screen, like a calculator; easier to read than analogue instruments since you don't have to interpret the numbers on a scale. (Section A-4.3)

The most common portable field pressure-measuring tool due to its many advantages over traditional instruments; it uses micro-pressure sensors that alter electrical resistance when pressure is applied and can measure positive, negative, or differential pressures; this tool is compact, can be used in any position, and does not require fluid. (Section A-4.1)

An electronic tool that combines the features of a voltmeter, an ammeter, and an ohmmeter; it measures electricity, voltage, and resistance and shows these measurements on a digital screen using numbers, making it easy to read and understand. (Section A-4.2 and Section A-4.3)

Ambient air introduced into the venting system of natural draft appliances, used to control draft and cool vent gases. (Section A-3.2)

A sealed combustion gas appliance that draws air from outside for combustion and vents exhaust gases directly outside, improving safety and efficiency. (Section A-1.2)

A ratio that tells you how far you need to be from an object to measure its temperature accurately with a thermometer; a higher D:S ratio means you can measure temperature from farther away, like using a zoom on a camera to focus on something far off. (Section A-4.2)

Equipment, such as a draft hood or damper, used in natural draft appliances to regulate airflow and ensure proper combustion. (Section A-3.2)

A device that helps control draft in natural draft systems, preventing downdrafts and allowing for safe venting even if the vent is blocked. (Figure 1, Section A-3.3)

Sensors that function on the principle that a combustible gas can be oxidized to produce heat; the resulting temperature change can be converted to a sensor signal; catalyst sensors are often used to detect hydrocarbons and rely on the presence of oxygen to function. (Section A-4.4)

Sensors that measure the concentration of a target gas by oxidizing or reducing the target gas at an electrode semiconductor; the absorption or desorption of the gas on the metal oxide semiconductor changes either the conductivity or the resistivity and the resulting current is measured and compared to a known baseline value. (Section A-4.4)

A number from 0 to 1 that indicates how much heat a material lets out as radiation; 1 means it gives off radiation well, like a perfect black object; lower numbers mean less heat is released. This matters in infrared thermometers, where knowing emissivity helps get accurate temperature readings by adjusting for how materials reflect or emit heat. (Section A-4.2)

Rules that set the minimum level of energy use for appliances, making sure they use energy in a smart way and help save power. (Section A-1.3)

A ventilation system similar to HRV but also transfers moisture between the outgoing and incoming air streams to maintain balanced humidity levels in the building. (Section A-3.4)

A Canadian program that identifies products meeting high-efficiency standards for energy use, helping consumers choose energy-saving appliances. (Section A-1.3)

Extra air supplied to the combustion process beyond the amount required for perfect combustion, typically 20-30% more than the theoretical amount needed for stoichiometric combustion. This ensures that all fuel is burned efficiently and completely. (Section A-3.1 and Section A-3.2)

The leakage of room air out of the building. (Section A-3.4)

A device that measures the amount of hydrocarbons in a sample; it burns the sample in a hydrogen-air flame, which produces ions if hydrocarbons are present; these ions create an electric current when they hit a metal plate, and the FID measures this current to determine the concentration of hydrocarbons; the device includes a portable hydrogen cylinder for the flame. (Section A-4.4)

A safety design feature in gas water heaters that prevents the ignition of flammable vapours outside the combustion chamber. Especially important in areas like garages where flammable liquids may be stored. (Section A-1.2)

A device that features a large temperature-sensing bulb connected to the instrument via a capillary tube; it employs a Bourdon tube mechanism similar to a pressure gauge: as the temperature of the enclosed liquid or gas varies, so does the pressure within the tube; these devices, also referred to as vapor tension thermometers, offer the advantage of remote temperature reading capabilities. (Section A-4.2)

The gases produced as a result of combustion, including carbon dioxide (CO₂), water vapor (H₂O), and nitrogen (N₂). (Section A-3.2)

An instrument designed to measure the pressure of fluids, usually gases or liquids; it features a U-shaped tube filled with a liquid like mercury, water, or light oils; the column will rise or fall until the weight of the liquid column balances the pressure differential between the two ends of the tube. The simplest version is the U-tube manometer. (Section A-4.1)

A type of power burner where the fan or blower is located upstream of the combustion zone to force air into the combustion chamber. (Section A-3.3)

The amount of gas flowing through an appliance, typically measured in cubic feet per hour (CFH), and used to calculate air supply requirements. (Section A-3.2)

A device used to control and maintain gas pressure at a safe, usable level for gas appliances. (Section A-2.2)

The pressure measurement by most gauges, this is the pressure measurement relative to atmospheric pressure as the zero point. (Section A-4.1)

The amount of heat a machine or appliance, like a water heater, can produce. It shows how much energy it transfers to heat things up. (Section A-1.3)

A system that recovers heat from outgoing exhaust air and transfers it to incoming fresh air, helping to improve energy efficiency and indoor air quality. (Figure 5, Section A-3.4)

A non-vented heating appliance that uses a porous burner surface to radiate high levels of heat, often used in large open areas like warehouses or patios. (Section A-1.2)

A type of tankless water heater equipped with a small buffer tank and a circulation pump. This design supports hot water recirculation systems and helps maintain consistent temperature delivery. (Section A-1.2)

A compound made of hydrogen and carbon atoms. Most fuel gases, like natural gas, propane, and butane, are hydrocarbons. (Section A-3.1)

A device used to measure lower range pressure readings, such as air flow measurements. By inclining the manometer, you can spread one inch of vertical lift over a much greater length, allowing the scale to be accurate to hundredths of an inch of WC [water column]. (Section A-4.1)

Occurs when there is insufficient oxygen for the fuel to burn completely, producing hazardous byproducts like carbon monoxide (CO), soot, and aldehydes. (Section A-3.1)

A type of power burner where the fan or blower is located downstream of the combustion zone, creating draft by drawing gases out of the combustion chamber. (Section A-3.3)

The unintentional introduction of outside air into a building; also referred to as air leakage. (Section A-3.4)

Also known as laser sensors, are based on absorption of infrared radiation as it passes through a volume of gas; the laser light beam emits a specific wavelength that is absorbed by methane, and when the laser hits methane, the methane absorbs some laser energy; the concentration of gas is proportional to the amount of specific IR light absorbed and is displayed in ppm concentrations; this sensor does not have to be placed into the gas to detect it and can be used for remote sensing at distances up to 30 metres. (Section A-4.4)

An Instrument that measures temperature by detecting thermal radiation emitted by the object being measured, often referred to as black-body radiation; also known as a laser thermometer due to use of a laser for aiming, or as a non-contact thermometer or temperature gun because it can measure temperature from a distance; by assessing the amount of infrared energy emitted and considering emissivity, infrared thermometers can estimate the object's temperature within a specified range; belongs to the category of devices known as "thermal radiation thermometers." (Section A-4.2)

The entry or movement of soil gases. (Section A-3.4)

A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. (Section A-4.3)

A liquid-crystal display (LCD) is a flat screen that uses liquid crystals to change how light passes through. It doesn't make its own light but uses a backlight or reflector to show images in color or black and white. (Section A-4.3)

A thermometer that consists of a small reservoir and a fine tube; the reservoir, or bulb, is filled with a fluid like colored alcohol or mercury; when the temperature changes, the liquid's volume changes, causing the liquid level in the tube to rise or fall. (Section A-4.2)

Lower explosive limits (LEL) is the lowest concentration of a flammable gas or vapor in the air that can ignite or explode when there is a source of ignition present. It's important to know LEL to stay safe when working with potentially explosive gases. (Section A-4.4)

A highly accurate pressure gauge for measuring draft conditions, determining pressure drop, or adjusting gas regulators. It uses a very sensitive diaphragm that has a pressure connection to each side. (Section A-4.1)

The air supplied in sufficient quantity to make up for air exhausted to outdoors. (Section A-3.4)

Instructions or details provided by the maker of a product, explaining how the product should be used, installed, and maintained. (Section A-1.3)

Draft that is created with the help of a mechanical fan or blower to move air and combustion gases, often used in high-efficiency appliances. (Section A-3.3)

The ductwork used in gas dryers to vent humid air and combustion by-products to the outdoors, as required by code. (Section A-1.2)

(Metal-Oxide-Semiconductor Field-Effect Transistor); A small electronic part that helps turn gas appliances on or off safely. It controls how electricity flows to important safety parts like sensors or shut-off devices. (Section A-1.2)

A type of draft where the movement of air is created by the buoyancy of hot combustion gases, which are lighter than cooler outside air. (Section A-3.3)

A fossil fuel primarily composed of methane, used as a common energy source in residential, commercial, and industrial applications. (Section A-2.2)

Resistors with a negative temperature coefficient, which means that their resistance decreases as the temperature increases; primarily used as resistive temperature sensors and current-limiting devices; unlike RTDs, which are made from metals, NTC thermistors are generally made of ceramics or polymers; their temperature sensitivity ranges from approximately -3% to -6% per degree Celsius. (Section A-4.2)

A tool used to measure how much something resists the flow of electricity (electrical resistance); it tells you the resistance in units called ohms (Ω); multimeters can serve as ohmmeters when set to resistance-measuring mode; to measure resistance, an ohmmeter applies a current to the circuit or component under test. (Section A-4.2 and Section A-4.3)

A pascal is the SI unit of pressure, equal to one newton per square meter (approximately 0.000145 pounds per square inch, or 9.9 × 10 atmospheres). (Section A-2.1)

When fuel burns with just the right (theoretical or mathematically exact) amount of oxygen, leaving only carbon dioxide (CO₂) and water (H₂O) as products. It’s a perfectly balanced reaction, but it's hard to achieve in real life because it's difficult to get the exact mix of oxygen and fuel. (Section A-3.1)

Approved assemblies of pipes, tubes, hoses, and fittings used to safely transport gas from the meter or tank to appliances. (Section A-2.2)

Resistors with a positive temperature coefficient, which means that the resistance increases with increasing temperature; they are made from materials such as silicon or barium titanate, known for their high resistance properties, and they have various uses such as temperature sensors, self-regulating heaters, and resettable fuses. (Section A-4.2)

An instrument for measuring or adjusting small electrical potentials. (Section A-4.2)

A burner with mechanical draft that generates sufficient pressure to overcome resistance in the combustion chamber, appliance, and venting system. (Section A-3.3)

A mechanical draft system used to assist venting in natural draft appliances, often used to overcome venting challenges like excessive negative pressure. (Section A-3.3)

The analysis of an applied force by a fluid (liquid or gas) on a surface; pressure is measured in units of force per unit of surface area. (Section A-4.1)

The portion of combustion air mixed with the fuel gas before ignition, typically one-third of the total combustion air. (Figure 2, Section A-3.2)

A hydrocarbon gas used as a fuel, often stored in tanks or cylinders, commonly used where natural gas service is unavailable. (Section A-2.2)

The pressure exerted by a force of one pound-force applied over an area of one square inch is defined as 1 psi (pound per square inch). In the International System of Units (SI), 1 psi is approximately equal to 6,895 pascals. PSI is a unit of pressure in both the US customary and imperial systems. It is also sometimes referred to as pound-force per square inch. (Section A-2.1)

The term "pound per square inch absolute" (psia) specifies that the pressure measurement is relative to a vacuum, as opposed to ambient atmospheric pressure. Note: pounds per square inch gauge is "psig" whereas pounds per square inch absolute is "psia." (Section A-2.1)

PSIG stands for "pounds per square inch gauge" and refers to the pressure measured by a gauge or other pressure measurement device. It indicates the difference between the pressure inside a pipe or tank and the atmospheric pressure (atm). Note: pounds per square inch gauge is "psig" whereas pounds per square inch absolute is "psia." (Section A-2.1)

The process of removing air or other gases from piping systems before gas is introduced, critical for safe appliance operation. (Section A-2.2)

A type of remote-sensing thermometer that measures the temperature of a surface without making direct contact; it determines temperature by detecting the thermal radiation emitted by the surface, which rises as the temperature increases. (Section A-4.2)

Methods used to reduce the presence of radon gas in a building, such as installing a subfloor depressurization system to create a pressure difference that prevents radon from entering the building. (Section A-3.4)

A metal or plastic tag on an appliance that shows important details, like how much power it uses, how to install it safely, and any safety standards it meets.(Section A-1.3)

A device that measures temperature by detecting changes in electrical resistance; RTDs can have a range of –200°C to +500°C. (Section A-4.2)

The additional air required to complete the combustion process, typically two-thirds of the total combustion air. (Section A-3.2)

The Seebeck effect happens when two different metals or materials are connected at two points and there is a temperature difference between those points; the temperature difference creates a small electric voltage; this effect can be used to measure temperatures or convert heat into electricity. The effect was discovered in 1821 by Thomas Johanan Seebeck. (Section A-4.2 and Section A-4.3)

The heat that causes a change in temperature of a substance and can be felt or measured by a thermometer; it is the heat exchanged by a body or system that changes its temperature without altering its phase, volume, or pressure; for instance, sensible heat warms water but does not melt ice or evaporate water. (Section A-4.2)

Devices used for measuring velocity and static pressures, conducting leakage, fan, and blower tests, calibrating control devices, checking gas pressure, and various other applications; consist of a flexible tube that can be rolled up compactly for easy handling and storage, and when unrolled, it can be attached to vertical steel surface with the built-in magnetic clips; the tube connectors are also shutoff valves that prevent the loss of fluid. (Section A-4.1)

A mixture of air, water vapour, and pollutants, such as radon, that enters a building through below-grade leaks in the building envelope, potentially affecting indoor air quality. (Section A-3.4)

The phenomenon where hot air rises due to its lower density, creating a natural flow of air into and out of buildings, chimneys, and vents. (Section A-3.3)

A device that transforms thermal energy into other physical forms such as mechanical energy, pressure, or electrical signals. For instance, a thermocouple generates an electrical potential difference based on temperature variations across its terminals. (Section A-4.2)

A thermal trap prevents cold air from entering the system while allowing hot air to escape, helping maintain the right temperature for combustion air and ensuring safe fuel burning. (Figure 2, Section A-1.1)

A type of semiconductor resistor whose resistance varies significantly with temperature, unlike standard resistors (the term "thermistor" combines "thermal" and "resistor"); these serve as temperature sensors in diverse applications and are categorized into two types: NTC (negative temperature coefficient) and PTC (positive temperature coefficient). (Section A-4.2)

Also referred to as a "thermoelectrical thermometer," an electrical device composed of two different electrical conductors that form an electrical junction; through the Seebeck effect, generates a voltage that varies with temperature, allowing for temperature measurement; extensively used as temperature sensors. (Section A-4.2)

A component used in some gas appliances to shut off the gas supply in case of sensor failure or unsafe operating conditions, often used with CO detectors. (Section A-1.2)

A cylindrical fitting designed to shield temperature sensors used for monitoring industrial processes; consists of a closed-end tube that is installed on the wall of piping or vessels where the fluid flows, safeguarding the temperature sensor inside. (Section A-4.2)

A thermocouple with Chromel and Alumel alloy wires, offering a broad temperature range from −270°C to 1,260°C; it generates an output of 6.4 to 54.9 mV across this range and excels in rugged environments and diverse atmospheres; Due to its versatility, widely employed as a temperature sensor, though it may not provide optimal accuracy for measuring smaller temperature differentials better than ±0.7°C. (Section A-4.2)

A self-contained, fan-forced, vented gas heater typically suspended from ceilings in garages or industrial spaces for localized space heating. (Section A-1.2)

A type of gauge that will register the amount of pressure below the atmospheric pressure. (Section A-4.1)

See flexible capillary dial thermometer. (Section A-4.2)

The intentional introduction of outdoor air into a space to control indoor air quality by diluting and displacing indoor pollutants; can also be used for purposes of thermal comfort or dehumidification. (Section A-1.2; Section A-3.4)

A guarantee from the manufacturer that a product will be free from defects for a certain period, with free repairs or replacements offered if needed. (Section A-1.3)

A method for measuring pressure, defined as the pressure produced by a 1-inch by 1-inch column of water of a specified height; useful for expressing low pressures, such as describing 0.072 psi as 2 inches of water. (Section A-4.1)

Microscopic water molecules that are suspended in air. (Section A-3.1, Section A-3.2, and Section A-3.4)

A gas fireplace that can be safely installed close to combustible materials because it is heavily insulated. It is designed for new construction or renovations where no existing fireplace is present. (Section A-1.2)