What is not true for LPG?

Concept

LPG (Liquefied Petroleum Gas) is a fuel obtained from petroleum refining, consisting mainly of propane (C₃H₈) and butane (C₄H₁₀), stored as a liquid under pressure. Its properties as a domestic and industrial fuel — low residue on combustion, high heat output, and the colour of its flame — all follow from this propane–butane composition, not from methane (CH₄), which is instead the chief constituent of natural gas / CNG.

Application

Check each statement against LPG's actual composition and combustion behaviour:

• Clean fuel — complete combustion of propane/butane releases mainly carbon dioxide and water vapour, with negligible soot, ash, or particulate residue, so LPG is genuinely a clean fuel.

• High calorific value — LPG's calorific value is high (roughly 45–46 MJ/kg), among the highest of common domestic fuels, which is exactly why it heats efficiently.

• Blue flame — with adequate air supply, propane/butane combustion is complete and produces a steady blue flame; an insufficient air supply instead gives a yellow, sooty flame.

• Methane emitting — LPG's main constituents are propane and butane, not methane, so calling LPG "methane emitting" misattributes its composition; this is the false statement among the four.

Cross-check

Compressed Natural Gas (CNG), not LPG, is the fuel whose principal component is methane. Keeping this LPG-vs-CNG distinction in mind confirms that the methane-emission claim does not hold for LPG, while the other three properties (clean burning, high calorific value, blue flame) are all well documented for propane–butane combustion.