Butane - a type of LPG

Butane is predominantly stored in blue Calor LPG cylinders / bottles, in a range of sizes. Like propane, it is an LPG (Liquefied Petroleum Gas), existing as a vapour (gas) at ambient temperature and pressure conditions, yet easily liquefied by cooling or applying moderate pressure.

A far higher boiling point than propane makes butane only suitable for outdoor use during milder months. Butane cylinders can be used indoors making them the Calor LPG fuel of choice for portable heater appliances used internally.

Butane is mainly used for portable heaters, barbecueing, and caravanning.

Butane - the technical explanation

Butane, a saturated hydrocarbon gas with the chemical formula C4H10, belongs to the Alkanes (previously known as Paraffins) family of hydrocarbon gases. Its chemical structure is given in the diagram to the right:

Commercial butane, the form generally supplied in the UK, primarily consists of butane (n-butane and iso-butane) along with concentrations of other hydrocarbon gases, such as propane and butanes.

The specification of commercial butane, is defined in BS 4250, the British Standard ‘Specification for commercial butane and commercial propane’.

Volume

The ability to liquefy under modest pressure distinguishes butane from natural gas. When liquefied, the volume occupied significantly reduces, making it easy to store and transport in specially constructed pressure vessels (e.g. Calor LPG cylinders).

An expansion ratio of approximately 233:1 from its vapour to liquid state means one volume of liquid butane produces 233 volumes of gas.

Density

Butane vapour is around 2.08 times denser than air, meaning it sinks to a low level when released in the atmosphere.

For this reason, butane cylinders cannot be stored below ground or near drains and cellar openings. Butane-fuelled appliances must not be used within cellars or basements.

Flammability

Butane mixed with correct proportions of air produces a highly flammable mixture, with flammability range of between 1.8% and 9.5%, by volume of gas in air. Outside this range the mixture is either too lean or rich to propagate a flame.

Calorific Value

The Calorific Value (CV) of a fuel mixture is the amount of energy released when a known fuel quantity undergoes combustion.

Butane has a CV of 126MJ/m3 whereas natural gas has a CV of 38MJ/m3, giving it a far greater heat energy release per unit volume, as well as a difference in air requirement and other combustion characteristics.

Butane-fuelled appliances must therefore have adequate means of ventilation, to ensure complete fuel combustion.

Regular servicing by suitably qualified and competent individuals will ensure these requirements are met and appliances perform correctly and safely.

Volatility

Butane is less volatile than propane. A boiling point of approximately -0.5ºC and a vapour pressure of around 2 bar / 30 psi (at 15ºC) makes it more suitable than propane for appliances where Calor LPG cylinders may be used indoors.

Odour

Butane is a colourless and odourless gas. For safety reasons a stenching agent of mercaptans (mainly ethyl mercaptan) and organic sulphides is added to butane to ensure leakages are easily detected by the distinctive and unpleasant smell.

Your Gas Needs

If you are unsure which Calor LPG cylinder / bottle to use, please consult our simple guide to selecting the right one.

Persons involved in the storage and handling of butane cylinders should have adequate information, training and supervision.