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  • Last Updated: 21 July 2021

Liquefied Petroleum Gas: LPG – What is LPG?

LPG – liquefied petroleum gas or liquid petroleum gas – (LP gas), the constituents of which are propane and butane, are flammable hydrocarbon fuel gases used for LPG heating, cooking and vehicles.
Liquefied Petroleum Gas is typically referred to by its acronym – LPG. LPG is mixture of flammable hydrocarbon gases that include propane, butane, isobutane and mixtures of the three LPG gases. LPG is commonly used for home heating gases, cooking, hot water, and autogas – fuel for LPG cars and vehicles.
LPG gas comes from oil and gas wells, as it is a fossil fuel. LPG gas manufacturing process includes natural gas processing and the crude oil refinery process.
LPG, liquefied through pressurisation, comes from natural gas processing and oil refining.
In different countries, the LPG heating fuel gases supplied can be propane, butane or propane-butane blends.
In Australia, LPG is just propane.  To explain LPG, Propane is LPG but not all LPG is propane.

What is LPG Made Up Of?

LPG – Liquefied petroleum gas or liquid petroleum gas, also denoted as just propane or butane, are both flammable hydrocarbon gases used as fuel for LPG heating gases, cooking and vehicular fuel.

LPG is made up of carbon and hydrogen atoms forming propane and butane whilst natural gas is made up of lighter methane, the simplest carbon and hydrogen molecule.

LPG is comprised primarily of propane and butane LPG heating gases, whilst the natural gas primary constituent is methane. LPG is made up of a group of flammable hydrocarbon gases that are liquefied through pressurisation and commonly used as fuel. Natural gas is liquefied cryogenically.

LPG is made up of a number of gases under the LPG products label, including propane, butane, isobutane and mixtures of these gases and are also referred to as natural gas liquids – NGL.

LPG is stored in steel vessels ranging from small BBQ gas bottles to larger gas cylinders and tanks.


What is LPG – Explain LPG – Summary:

LPG – Liquefied petroleum gas or liquid petroleum gas (LP gas) – is primarily the flammable hydrocarbon gases propane and butane used as fuel for gas heaters, cookers and LPG vehicles. LPG is also referred to as “bottled gas”.

To explain LPG, there are a number of fuel gases that fall under the LPG products label, including propane, butane (n-butane) and isobutane (i-butane), as well as mixtures of these gases and are also referred to as natural gas liquids – NGL. In Summary:

1. LPG (or LP Gas) is the acronym for Liquefied Petroleum Gas or Liquid Petroleum Gas.
2. LPG products are made up of a group of flammable hydrocarbon gases that are liquefied through pressurisation and commonly used as fuel.
3. LPG comes from natural gas processing and petroleum refining.
4. LPG gases can all be compressed into liquid at relatively low pressures.
5. LPG is frequently used for fuel as LPG heating gases, cooking, hot water and vehicles, as well as for refrigerants, aerosol propellants and petrochemical feedstock.
6. LPG is generally stored, as a liquid, in steel vessels ranging from small BBQ gas bottles to larger gas cylinders and LPG storage tanks.
7. LPG is mixture of flammable hydrocarbon gases that include propane, butane, isobutane and mixtures of the three LPG gases.

LPG Attributes Chart – Table

LPG Attributes Table
LPG Attributes Propane Butane
Chemical Formula C3H8 C4H10
Energy Content: MJ/m3 95.8 111.4
Energy Content: MJ/kg 49.58 47.39
Energy Content: MJ/L 25.3 27.5
Boiling Temp: Cº -42 -0.4
Pressure @ 21ºC: kPa 858.7 215.1
Flame Temp: Cº 1967 1970
Expansion: m3/L 0.270 0.235
Gas Volume: m3/kg 0.540 0.405
Relative Density: H2O 0.51 0.58
Relative Density: air 1.53 2.00
L per kg 1.96 1.724
kg per L 0.51 0.58
Specific Gravity @ 25ºC 1.55 2.07
Density @ 15ºC: kg/m3 1.899 2.544

 Note: Some numbers have been rounded.

The following short video (8:29) explains all of the basics of LPG…

LPG Gas Mixture

LPG – Liquefied Petroleum Gas – (Autogas) is primarily comprised of propane, butane, and isobutane in a range of mixtures. LPG heating gases are produced as a co-product of crude oil refining and natural gas processing. The constituents of LPG are gaseous at 20°C and 1 atmosphere pressure (NTP).

Gas in LPG Tanks

Gas in LPG tanks is LPG liquid under pressure, from 0 kPa at -42°C to 1794 kPa at 54°C, and turns back into gas when you release some of the pressure. The LPG (propane) exists as both liquid and vapour (gas) within the cylinder. See image below.

LPG Fuel

LPG is a fuel gas. Liquefied petroleum gas or liquid petroleum gas – LPG – also identified as propane or butane, are flammable hydrocarbon gas mixtures used as fuel in vehicles, as Autogas, and as home heating gases and cooking fuel.

LPG Full Form – LPG Meaning – What Does LPG Stand For?

LPG stands for the acronym abbreviation for either Liquefied Petroleum Gas fuel or Liquid Petroleum Gas fuel. To explain LPG, LPG products mean the flammable hydrocarbon gases propane, butane and isobutane, used for heating, cooking, hot water and vehicle fuel.

LPG products go by many names but they all mean the same gases – propane and butane – and this can sometimes be confusing.

It is also called LPG Gas, LP Gas, Propane, BBQ Gas, Camping Gas or Autogas.

LPG Class

Butane emits more carbon than propane or a propane and butane LPG mix, as butane has 4 carbon atoms vs 3 for propane.

LPG fuel is not just a single gas. There are a number of gases that fall under the LPG fuel type category. The most common of these LPG products include propanebutane (n-butane) and isobutane (i-butane), as well as mixtures of these gases.

LPG class Hazchem Code is 2YE whilst the LPG Transport Hazard Class is 2.1. LPG GHS Classifications is Flammable Gases: CATEGORY 1. Hazard Statements classes are H220 – Extremely flammable gas and H280 – Contains gas under pressure; may explode if heated.

LPG Heating Gases

LPG heating gases are propane and butane. They are commonly used for generating heat for home heating, hot water, cooking and commercial applications, including boilers. Isobutane is the other common LPG gas but is not typically used for heating. The main uses of isobutane are as a petrol (gasoline) additive, as a refrigerant and as a feed stock for plastics.

Where Does LPG Come From?

LPG comes from drilling oil and gas wells.

It is a fossil fuel that does not occur in isolation.

LPG products are found naturally in combination with other hydrocarbon fuels, typically crude oil and natural gas.

LPG is produced during natural gas processing and oil refining.

It is isolated, liquefied through pressurisation and stored in pressure vessels.

How is LPG Stored?

LPG is stored in pressure vessels.

As such, it is almost always stored in its liquid form.

These can range from small camping cannisters to BBQ gas bottles to larger gas cylinders and much larger LPG tanks or bullets.

LPG fuel storage depots may consist of very large storage spheres, known as Horton Spheres (see accompanying image).

LPG can also be stored underground in specially built or prepared caverns.

Gas Bottles – LPG Gas Bottles for Home

Gas bottles range from small portable cylinders to large tanks and bulk storage vessels. LPG gas bottles are typically steel vessels for storing the common LPG gases, propane or butane. Homes and small businesses typically use either a 45kg gas bottle, 90 kg gas bottle or the larger 210kg LPG gas bottle sizes (gas cylinder sizes) and cylinder capacity.

High volume users have the larger LPG gas tank sizes (LPG tank sizes).

BBQ gas bottle sizes come in 4kg & 9kg gas bottle dimensions, cylinder capacity & gas bottle sizes (propane gas bottle sizes). Small LPG gas bottles are portable, as used in camping.

LPG & Natural Gas Liquids – NGLs

The typical LPG products heating fuel gases – propane and butane – are regarded as Natural Gas Liquids – NGLs.

However, not all NGLs are LPG.

Natural gas liquids, also called Condensate, include other hydrocarbons, too.

Interestingly, LNG – liquefied natural gas – is NOT a natural gas liquid.

What are Natural Gas Liquids – NGLs?

Raw natural gas, as it comes out of the ground, contains a number of fuel gases and compounds, as well as impurities.

However, it is predominantly methane (CH4) gas, which is more commonly known as natural gas.

The raw natural gas must be processed to obtain pipeline quality clean, dry natural gas (methane), including the removal of impurities.

NGLs – Natural Gas Liquids – or condensate are the heavier hydrocarbons that remain after the methane (natural gas) and impurities are removed.

NGLs include isobutane, ethane, ethene, propene, isobutene, butadiene, pentane, pentene and pentanes plus, as well as propane and butane.

Natural gas liquids (NGL) range from 1% to 10% of the raw natural gas flow.

How is LPG Made?  What is the Production Process?

LPG is made during natural gas processing and oil refining.

LPG is separated from unprocessed natural gas using refrigeration.

LPG is extracted from heated crude oil using a distillation tower.

This LPG can be used as is or separated into LPG products three primary parts: propane, butane and isobutane.

It is stored pressurised, as a liquid, in cylinders or tanks.


LPG is Refined from Oil & Natural Gas

LPG is produced during natural gas processing and petroleum refining.

Propane does not occur naturally in isolation.

LPG processing involves separation and collection of the gas from its petroleum base.

LPG is isolated from the hydrocarbon mixtures by separation from natural gas or by the refining of crude oil.

Both processes begin by drilling oil wells.

The gas/oil mixture is piped out of the well and into a gas trap, which separates the stream into crude oil and “wet” gas, which contains LPG and natural gas.

The heavier crude oil sinks to the bottom of the trap and is then pumped into an oil storage tank for refining.

Crude oil undergoes a variety of refining processes, including catalytic cracking, crude distillation, and others.

One of the refined products is LPG.

The “wet” gas, off the top of the gas trap, is processed to separate the gasoline (petrol) from the natural gas and LPG.

Once refined, LPG products are stored as a liquid under pressure in gas bottles – cylinders or tanks. 45kg gas bottles shown below:

The natural gas, which is mostly methane, is piped to towns and cities for distribution by gas utility companies.

The petrol is shipped to service stations.

The LPG fuel also enters the distribution network, where it eventually finds its way to end users, including Home LPG and Commercial LPG users all around Australia and the world.

At the point of use it once again becomes a gas.

What is LPG Used For?   How is LPG Used in Your Home

LPG (liquefied petroleum gas) is used in your home, including cooking, heating, hot water, autogas, aerosol propellant, air conditioning refrigerant and back-up generator applications. LPG used in your home is typically supplied in 45kg LPG gas bottles.

LPG – Liquefied Petroleum Gas – has hundreds, if not thousands, of LPG uses including hot air balloons

It is used in leisure time activities including caravans, boats, recreational vehicles and camping.

Business and industry use LPG fuel for a multitude of processes including steam boilers, kilns, ovens and LPG forklifts.

LPG products are also employed as a propellant, refrigerant, vehicle fuel and petrochemical feedstock.

Crop and produce drying, heating greenhouses, hot water for dairies, irrigation pumps and heating animal enclosures are just some of the agricultural applications for LPG.

LPG fuel for transport is also a big user of LPG (Autogas).

LPG products can be either as propane or propane mixed with butane, to fuel various vehicle types.

There are also many, many more LPG applications, including power generation and the hospitality industry.

How is Cooking Gas Produced

Cooking gas is produced using the LPG gas manufacturing process that occurs during natural gas processing and oil refining. That’s because cooking gas is LPG (propane) and not some different gas.

Cooking gas can also be produced using natural gas or piped gas.

Cooking Gas is an LPG Fuel

Cooking gas is no different from the typical gas provided in a given country.

If it is bottled gas, it is the regular LPG heating fuel gas supplied in that country.

If it is piped gas, it is most often natural gas, which is primarily methane.

Cooking Gas Cylinder

A cooking gas cylinder can be a 9kg BBQ gas bottle, a 14.2kg domestic cooking gas cylinder or a home 45kg LPG gas bottle. Cooking gas cylinders are typically steel or aluminium vessels for storing the common LPG gases – propane or butane. Cooking gas cylinder sizes are contingent upon the usage, the requisite volume of gas and the location of the gas cylinder installation.

LPG Fuel – Fuel Type LPG – Which Gas or Gases are Present in LPG?

LPG fuel is not just a single gas.

There are a number of gases that fall under the LPG fuel type category.

The most common of these LPG products include propanebutane (n-butane) and isobutane (i-butane), as well as mixtures of these gases.

The fuel type LPG is made up of other gases that also fall under the LPG products label, including ethane, ethylene, propylene, butylene and isobutylene, as well as mixtures of these gases.

In Australia, fuel type LPG is propane.

In the USA, the fuel type LPG is also propane and they call it “propane” instead of “LPG”.

In New Zealand, LPG is a mixture of propane and butane.

In the UK, consumers have choices LPG fuel types.  It is referred to as either propane, butane or LPG, depending on what gas is present in the customer’s choice.

LPG (Propane) Vaporisation – How LPG Boils

Did you know that every time you turn on one of your gas appliances, the LPG in your gas bottles starts to boil?

If you could see though the steel, you would also notice that it looks just like water boiling.

The big difference is that it happens at -42°C or -44°F.

Liquid LPG changing to gas vapour is called vaporisation.

To boil, the liquid LPG draws heat from the steel walls of the gas bottle which, in turn, get heat from the ambient air.

LPG liquid boils and turns back into gas vapour when you release some of the pressure in the gas bottle by turning on your gas appliance.

As with water, the more heat that is applied, the more rapidly it boils, vaporising at a faster rate.

The vapour pressure in the bottle also increases with temperature, as explained below.

So, as the steel of the bottle draws heat from the ambient air heat, cold weather will slow down the rate of vaporisation.

Vaporisation also makes the gas bottle feel colder than the ambient temperature.

The gas bottle gets even colder when you are actually using the gas.

The LPG gas vapour is held in the top of the bottle and the liquid LPG at the bottom, as shown in the image above.

Almost all of the uses for LPG involve the use of the gas vapour, not the liquefied gas

LPG Composition – What is LPG Made Up Of?

LPG is made up of the gases that fall under the LPG products label, including ethane, ethylene, propane, propylene, normal butane, butylene, isobutane and isobutylene, as well as mixtures of these gases.

The two most common LPG products are Propane and Butane.

Isobutane (i-butane) is an isomer of butane with the same chemical formula as butane but different physical properties.

Isobutane is converted from butane in a process called isomerization.

It is classified as LPG, along with propane, butane and mixes of these gases.

LPG Gas Chemical Formula – LPG Chemical Formula

There are a number of LPG gas chemical formulas (formulae). Starting with the lowest carbon LPG chemical formula, the Ethane chemical formula is C2H6. Propane chemical formula is C3H8. Butane and Isobutane both have the same chemical formula, C4H10, as isobutane is an isomer of butane. Pentane (n-pentane) chemical formula is C5H12, but is only a gas over 36.1°C. Heavier hydrocarbons (pentanes plus) are liquids or waxy solids.

LPG Properties Chart

LPG physical properties include specific gravity (density), boiling point, pressure, vapour expansion, energy content, combustion facts, flame temperature, flash point & more.

This chart shows some of the physical properties of propane, butane and isobutane…

LPG Pressure Varies with Temperature

As previously mentioned, when LPG is stored in a gas bottle, it is under pressure.

The term “pressure” refers to the average force per unit of area that the gas exerts on the inside walls of the gas bottle.

(LPG Pressure-Temperature Chart shown)

Pressure is measured in kilopascals (kPa) or pounds per square inch (psi).

LPG pressure can vary greatly based on temperature, as shown in the chart.The level of fill in the gas bottle comes into play when the LPG is being used, as it affects the rate of vapourisation.

As LPG is a liquefied gas, the pressure inside the cylinder will remain the same from full until the last of the liquid LPG is vapourised.

Then the pressure will fall quickly as the last of the LPG vapour is used, as well.

How Much Pressure is in an LPG-Propane Cylinder?

The pressure inside of an LPG 45kg cylinder, or larger vessel, is dependent upon the temperature of the vessel.

The higher the temperature, the higher the pressure of the LPG within the cylinder.

The pressure range for LPG (propane) is from 152 kPa (24 PSIG) at 0ºC to 1794 kPa (257 PSIG) at 54ºC.

The LPG – propane – exists as both liquid and vapour (gas) within the cylinder.

The term “pressure” refers to the average force per unit of area that the gas exerts on the inside walls of the cylinder.

The pressure drops to zero at -43ºC (which is just below the boiling point for propane) and the pressure becomes greater at even higher temperatures.

LPG is Heavier Than Air

In answer to the frequently asked question “Is LPG heavier than air”, the answer is “YES”.

For example, if the density of air is equal to 1.00, the density of propane is 1.53.

Butane is even heavier, at 2.00.  Isobutane is heavier still, at 2.07.

On the other hand, natural gas – methane – is lighter than air, at about 60% of the density of air.


In Australia, LPG is Propane.

Propane is the gas that is supplied to virtually all homes and most businesses that purchase LPG in Australia.

Propane is a flammable hydrocarbon gas with 3 carbon and 8 hydrogen atoms in a propane molecule.

The chemical formula of LPG gas (chemical formula for propane) is C3H8.  (Propane molecule model shown)

Propane is not made or manufactured, it is found naturally in combination with other hydrocarbons.

Propane is produced during natural gas processing and petroleum refining.

Propane processing involves the separation and collection of the gas from its petroleum base and other Natural Gas Liquids (NGLs).

Following its refinement, LPG is stored and distributed as a liquid under pressure until used, at which point it is utilised as either a liquid or a gas (vapour).

LPG is supplied in gas bottles that are either exchanged or refilled on site by LPG tankers.
Large users may utilise bigger LPG storage tanks.

Propane Combustion Formula

In the presence of sufficient oxygen, LPG burns to form water vapour and carbon dioxide, as well as heat.

Formula for Complete Combustion of LPG (propane):

Propane + Oxygen → Carbon Dioxide + Water + Heat
C3H8 + 5 O2 → 3 CO2 + 4 H2O + Heat
If not enough oxygen is present for complete combustion of LPG (propane), incomplete combustion occurs with water, carbon monoxide, and carbon dioxide being produced.

Formula for Incomplete Combustion of LPG (propane):

Propane + Oxygen → Carbon Dioxide + Carbon Monoxide + Water + Heat
2 C3H8 + 9 O2 → 4 CO2 + 2 CO + 8 H2O + heat



Butane (n-butane) is also considered to be LPG.

Butane is a flammable hydrocarbon gas that is liquefied through pressurisation.

The chemical formula for Butane is C4H10, with 4 carbon and 10 hydrogen atoms in a butane molecule. Technically, this is also a chemical formula of LPG gas. (Butane molecule model shown)

Butane is commonly used as a fuel, propellant and refrigerant, as well as a petrochemical feedstock.

Butane is supplied to businesses that require Butane, as opposed to propane.

Butane has some specific applications where it has advantages over propane.

Butane Combustion Formula

Assuming complete combustion, you get carbon dioxide and water:

Butane + Oxygen → Carbon Dioxide + Water + Heat

2 C4H10 + 13 O2 → 8 CO2+ 10 H2O + Heat

However, with incomplete combustion you can get carbon monoxide and water

Butane + Oxygen (insufficient) → Carbon Monoxide + Water + Heat

2 C4H10 + 9 O2 → 8 CO + 10 H2O + Heat

This would typically occur if the ratio of oxygen to butane was insufficient.

LPG Fuel: Autogas for Vehicles

Autogas is also LPG fuel.

Autogas that is sold at service stations can be propane or a propane/butane mix.

Not only is running an LPG car economical, but Autogas is also cleaner burning fuel than petrol, so engine life is actually extended and greenhouse gas emissions reduced.

LPG is Eco-Friendly

LPG heating gas is an eco-friendly choice, as it is a low carbon, low sulphur fuel.

LPG products result in lower CO2 emissions than other energy sources, such as coal fired electricity.

For example, with coal fired electricity, replacing your electric hot water system with a 6-Star LPG continuous flow hot water system may reduce the greenhouse gas emissions produced from your hot water use by about 75%.

Final Thoughts

LPG is a versatile, transportable, low carbon fuel.

Using it requires very little infrastructure, which makes it an excellent choice for developing countries, as well as developed countries.

LPG products are easy to transport, in cylinders or tankers, making it available virtually everywhere.

Delivery methods can range from very sophisticated to extremely basic.

From requiring considerable capital investment to virtually no investment at all.

Regardless of how it’s delivered, LPG is there when people need it.

Clean, safe and reliable energy for everyone everywhere.


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The information in this article is derived from various sources and is believed to be correct at the time of publication. However, the information may not be error free and may not be applicable in all circumstances.