Is LPG Heavier than Air? – Is LPG Lighter than Air?

Is LPG Heavier than Air – Is LPG Lighter than Air

LPG – propane is 1.55 times heavier than air.  LPG density (propane density) is 1.55 times heavier than air. LPG – propane gas weighs 1.898 kg/m³ vs air at 1.225 kg/m³ (at 15°C and 1 atm).

Butane is slightly more than twice the weight of air. Butane is 2.006 times heavier than air, under the same temperature and pressure conditions. Butane weighs 2.5436 kg/m³ whilst air weighs 1.225 kg/m³ (with both 15°C at 1 atm), so slightly more than twice the weight.

Butane has a molar mass of 58.124 g/mol vs 28.97 g/mol for air. 

LPG (propane gas) is not lighter than air. In fact, LPG is over 50% heavier than air at sea level (1 atm). Butane relative density is not lighter than air. Butane gas relative density is heavier than air. 

So, LPG is heavier than air.

As a result, LPG gas, both propane and butane, will settle in low places.

LPG Density – Is LPG is Lighter than Air

No, LPG is not lighter than air. LPG is heavier than air. Propane gas weighs 1.898 kg/m³ vs air at 1.225 kg/m³. (All at 15°C and 1 atm). Specific Gravity of LPG (propane gas) is 1.55 (air = 1.00).

Butane is also not lighter than air. Butane is heavier than air. Butane gas weighs 2.5436 kg/m³ whilst air weighs 1.225 kg/m³. Butane is a bit more than 2 times heavier than air. 

LPG Density Chart – LPG (Propane & Butane)

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

LPG gas (vapour) is heavier than air.

LPG gas – 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)

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

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

Unlike water, 1 kilogram of LPG does NOT equal 1 litre of LPG. 1kg of LPG has a volume of 1.96L. 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.

The specific gravity (SG) of liquid Butane is 0.601 (at 25°C). Butane is 601.26 kg/m³ (at boiling point of -0.4°C or 31.3°F)

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

LPG Liquid to Gas or LPG Gas to Liquid

Note that the following are gas to liquid or liquid to gas 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)