Elgas LPG Gas Blog

Is LPG Lighter than Air – Is Butane Heavier than Air

LPG gas is not lighter than air. LPG (propane) is heavier than air. Butane is also heavier than air.

In fact, LPG is over 50% heavier than air at sea level (1 atm).

As a result, LPG gas will settle in low places.

LPG Density - Is LPG is Lighter than Air

LPG is not lighter than air. LPG is heavier than air. LPG density (propane density) is 1.55 times heavier than air. Specific Gravity of LPG gas is 1.55 (air = 1.00). LPG weighs 1.898 kg/m3. Air weighs 1.225 kg/m3. (Both 15°C at 1 atm).

LPG Density Chart - LPG (Propane & Butane)
Is LPG (Propane & Butane)
Lighter or Heavier than Air
Density (Air=1)

At standard temperature and pressure – STP¹ – LPG is a gas.

LPG gas (vapour) is heavier than air.LPG (Propane & Butane) is Heavier than Air

The following apply to LPG, as a gas:

●  LPG – propane – weighs 0.1162 lbs/ft3.  Air weighs 0.0752 lbs/ft3.

Note that LPG gas is also referred to as “LPG vapour”. 

Vapour (vapor is the US spelling) is the more technically correct term.

Note that vapours are gases however not all gases are vapours.

¹STP - Standard Temperature and Pressure - is defined as 0°C (32°F) and 1 atm (14.7 psia or 0 psig)

Is Butane Heavier than Air - Is Butane Lighter than Air

Butane is heavier than air, Butane is not lighter than air. Butane gas is 2.08 times heavier than air.

Butane weighs 2.5436 kg/m3 (15°C at 1 atm). Air weighs 1.225 kg/m3. (15°C at 1 atm). So, Butane is a bit more than 2x heavier than air.

Butane is one of the gases, along with propane, that is classified as LPG.

Why It's Important to Know

In the event of an LPG gas leak, it is important to remember that LPG is heavier than air.

Leaking gas will settle to the lowest point, including basements and under houses.

Pits and drains are also obvious collection points.

So, if you have a leak, don't assume that all of the gas is gone just because you no longer smell it on the main level of your home.

Be sure that the gas has dissipated everywhere, even within the low spots inside and around your home.

LPG Density - Specific Gravity of Liquid LPG

Density of LPGLPG density is less than that of water. LPG density or specific gravity is about half that of water, with 1 litre equalling 0.51 kg (at 15°C). Unlike water, 1 kilogram of LPG does NOT equal 1 litre of LPG. 1kg of LPG has a volume of 1.96L.

LPG is a liquid when stored under pressure in a cylinder or other vessel.

Conversely, 1L of LPG (propane) weighs 0.51kg (at 15°C). 

Expressed in USA units of measure, 1 lb of propane (at 60°F) has a volume of 0.24 US gallons.

Conversely, 1 US gallon of propane (at 60°F) only weighs 4.23 lbs, instead of the 8.34 lbs it would weigh if it was water.

Propane is 580.88 kg/m3 (at boiling point of -42°C or -44°F)

Butane is 601.26 kg/m3 (at boiling point of -0.4°C or 31.3°F)

The specific gravity (SG) of liquid Butane is 0.601 (at 25°C)

LPG Liquid to Gas or LPG Gas to Liquid

Note that the following are liquid to gas or gas to liquid conversions:

●  LPG kg to m³ (1kg = 0.53m³) or m³ to kg (1m³ = 1.89kg)

●  LPG litres to m³ (1L = 0.27m³) or m³ to litres (1m³ = 3.70L)




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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.