Natural Gas Glossary




A device used in the home to perform domestic chores, such as a clothes dryer, dishwasher, refrigerator, toaster, etc.


The layer of gases that surrounds the earth.


The smallest unit of matter. Everything in the world is made of different combinations of atoms.



Biogas is a mixture of methane and carbon dioxide that is generated when bacteria degrade biological material in the absence of oxygen, in a process known as anaerobic digestion. Biogas can be burned in boilers to produce hot water and steam and to generate electricity. It can also be used as a vehicle fuel.


A hydrocarbon gas that is one of the ingredients in natural gas. Butane molecules consist of four carbon atoms and ten hydrogen atoms.


Cap rock

The cap rock keeps underground natural gas deposits from escaping upward. Granite is a common cap rock.

Carbon dioxide (CO2)

A colorless, odorless, nonpoisonous gas that is a normal part of the air we breathe. Carbon dioxide is exhaled by humans and animals, and is absorbed by green growing things and by the sea. Carbon dioxide molecules consist of one carbon atom and two oxygen atoms. A small amount of carbon dioxide is found in natural gas.

Carbon monoxide (CO)

A colorless, odorless, poisonous gas that is formed when fuel is burned without enough oxygen. Carbon monoxide alarms can be installed in the home to alert people to its presence. Carbon monoxide molecules consist of one carbon atom and one oxygen atom.

Chemical energy

Energy that is released by a chemical reaction.

Chemical reaction

A process that changes one substance into another substance. Chemical reactions that take place during digestion change energy in food into substances that the body can use to do work.

Climate change

Changes in temperature, rainfall, wind, and other aspects of the earth’s climate that last for an extended period.


A fuel consisting of black or brown rock that is taken out of the ground at large mines.


Capable of burning.


The process of burning.

Compressor station

A place where natural gas is pressurized to be sure it flows effectively through pipes.

Cubic foot (cf)

The most common unit of measurement of natural gas volume. It takes 8 gallons of liquid to equal 1 cubic foot. Burning 100 cubic feet of natural gas equals approximately 1 therm, a common gas measurement.

Cubic meter

A common unit of measurement of natural gas volume. It takes 1,000 liters of liquid to equal one cubic meter.



A movable plate for regulating the draft in a chimney.

Distribution main

Underground pipelines that carry natural gas from utilities to homes and businesses.


Electrical Energy

A form of energy that arises from the flow of electrons.


The basic particles that orbit the nucleus of an atom. The flow of electrons produces electricity.


The ability to change or move matter. It is sometimes also defined as the ability to do work.

Energy efficiency

Using less energy while getting more service from your appliances and equipment. You can do this by practicing energy-efficient behaviors or using energy-efficient technology, such as new types of appliances.


All the natural and living things around us. The earth, air, weather, plants, and animals all make up our environment.


A hydrocarbon gas that is one of the ingredients in natural gas. Ethane molecules each contain two carbon atoms and six hydrogen atoms.


Taken out. Natural gas is extracted from the earth through deep wells.



A flue is a pipe that carries the products of combustion out of a building. Fireplaces have flues that direct the smoke from a fire up the chimney. Natural gas appliances and equipment have flue pipes that vent to the outdoors.

Fossil fuels

Coal, oil, and natural gas are known as fossil fuels because they were formed from the remains of animals or plants that lived long ago.


A substance that can be used to produce heat.



A substance whose molecules are randomly moving so quickly that the molecules easily separate from one another. Gases will spread out and take on the shape and volume of whatever they are in—a jar, a room, or the atmosphere.

Gas bill

A statement received monthly from a natural gas utility showing how much natural gas your household used and how much you will need to pay for it.

Gas lines

Small pipes (1/4 to 1 inch in diameter) that carry natural gas to home appliances.

Gas meter

A device that records how much natural gas is being used in a building.

Gas trap

An arrangement of three types of rock that geologists look for when searching for natural gas: the source rock that produces the natural gas, the porous reservoir rock that holds the natural gas, and the cap rock that keeps the gas from escaping.


A person who studies the physical nature and history of the earth as his or her career.

Global warming

An increase in the earth’s temperature caused by human activities such as burning fossil fuels for energy. Burning these fuels releases carbon dioxide and other gases that make the earth’s natural greenhouse effect much stronger, trapping more of the sun’s heat in our atmosphere. Global warming is causing glaciers to melt and is changing sea levels and weather patterns.

Greenhouse effect

The greenhouse effect is the rise in temperature that the earth experiences because certain gases in the atmosphere absorb and radiate heat from the sun. This process occurs naturally and has kept the Earth’s temperature about 59 degrees F warmer than it would otherwise be. Current life on Earth could not be sustained without the natural greenhouse effect. Most scientists believe warming is happening because the greenhouse effect has become intensified primarily by the burning of fossil fuels, releasing an excess of carbon dioxide and other gases into the atmosphere.

Greenhouse gases

Carbon dioxide, methane, and ozone. These gases form a sort of clear layer around the earth that absorbs and radiates heat from the sun.



A hydrocarbon gas that is an ingredient of natural gas. Heptane molecules each contain seven carbon atoms and sixteen hydrogen atoms.


A hydrocarbon gas that is an ingredient of natural gas. Hexane molecules each contain six carbon atoms and fourteen hydrogen atoms.


A compound that contains only hydrogen and carbon atoms. Natural gas is a mixture of hydrocarbons.



The process of lighting a fire or causing a fuel to start burning.



A substance whose molecules are in constant, random motion but do not move as fast as those in a gas. A liquid can take on the shape of its container but keeps the same volume, no matter what container it’s in.


Mechanical energy

The energy of motion that can move objects from place to place.


A chemical added to natural gas that makes it smell like rotten eggs so people will know if natural gas is leaking.


A hydrocarbon gas that is the main ingredient in natural gas. Methane molecules each contain one carbon atom and four hydrogen atoms.


The smallest part of a substance that has all of the chemical properties of that substance.


Natural gas

A hydrocarbon gas found in the earth, composed of methane, ethane, butane, propane, nitrogen, carbon dioxide, hexane, heptane, and pentane.


A gas that is an ingredient of natural gas. Nitrogen molecules each contain two nitrogen atoms.

Nonrenewable fossil fuels

Fuels that can be used up because their quantities are finite – they cannot be easily made or “renewed”. Oil, natural gas, and coal are nonrenewable fossil fuels.

Nonrenewable resource

A resource that is limited. Fossil fuels (oil, coal, and natural gas) are considered nonrenewable resources because once they are used up we cannot create more of them.

Nuclear energy or nuclear power

Energy that is released from splitting atoms of radioactive materials (such as uranium) and then harnessed to generate electricity.


The center of an atom. The nucleus contains tiny particles called protons and neutrons. Orbiting around the nucleus are electrons.



A fossil fuel in liquid form that is obtained through wells drilled deep in the earth.

Oil seep

The appearance of oil on the surface of the ground that geologists use as a telltale sign of natural gas below, since oil and natural gas are usually found together.

One-call service

The utility locator service that should be called before digging into the ground. This service marks the location of buried utilities so people can work a safe distance away from them.



A hydrocarbon gas that is an ingredient of natural gas. Pentane molecules each contain five carbon atoms and twelve hydrogen atoms.

Pilot light

A small flame or spark used to ignite gas at a burner. Most newer appliances have electric pilots; older appliances have a small permanent flame.

Power plant

A place where electricity is generated and sent over wires to where it is used.

Processing plant

A place where natural gas is treated to remove impurities.


A hydrocarbon gas that is one of the ingredients in natural gas. Propane molecules each contain three carbon atoms and eight hydrogen atoms.


Radiant energy

Any form of energy radiating from a source, such as heat from the sun or a campfire, or light from a bulb.

Refining facility

A facility that takes a crude substance (such as oil) and turns it into products such as electricity, fuels, or gases.


If something is renewable it can be replaced or remade.

Renewable resources

Fuels that can be easily made or “renewed”. We can never use up renewable fuels. Types of renewable fuels are solar power, wind power, and hydropower.

Reservoir rock

A layer of porous sedimentary rock, usually sandstone or limestone. The natural gas migrates into the pores of the reservoir rock.


Seismic survey

One of the tests used by geologists to determine if rocks have the properties needed to contain natural gas underground.


A two- or three-dimensional record made by a computer that measures changes in the density of rock. Geologists analyze seismograms and use them to visualize the rock layers beneath the earth’s surface that might reveal possible natural gas and/or oil traps.

Service line

A pipeline that carries natural gas from a distribution main up to the gas meter at a building.


Something that is hard and firm, and is not a liquid or gas. The molecules in a solid move slowly enough that they merely vibrate in place, allowing the solid to keep its shape and volume.

Source rock

Rock that supplies the natural gas in a gas trap. The gas was generated by the decomposition of tiny sea plants and animals that died millions of years ago, sank to the muddy bottom, and became part of this rock. Shale is a common source rock.

Storage tanks

Large aboveground or underground tanks used to store natural gas for future use.



A unit of measurement for the use of natural gas that appears on a person’s monthly gas bill. Therms are the cubic feet of natural gas used, multiplied by a therm factor.

Therm factor

Determined by the utility and based on the energy content of the natural gas, which can vary by supplier. Some utilities use an average therm factor.


A device that controls the temperature of a heating or cooling system.

Transfer of energy

When one energy source moves or changes another source.

Transmission pipes

A network of large steel pipes that carry natural gas from processing plants to utilities.



A company or other organization that provides a service such as supplying electricity, natural gas, or water.



A movable part that controls the flow of a liquid or gas through a pipe or other channel.


The amount of space taken up by something.



A hole drilled or bored into the earth to bring up water, sulfur, natural gas, or petroleum.