Gas and Combustion · 4 lessons
Natural gas and LPG: what's different
The two fuels behave differently, and the differences explain several of the rules.
Our gas engineering path is in public beta: some lessons are still being checked. More sections are coming.
What each one is
Natural gas is mostly methane, piped to most homes. LPG is propane, butane or a mix, stored as a liquid under pressure in cylinders or tanks. An appliance must match its fuel.
Why gas smells
Fuel gas has an odorant added so a leak can be smelt. Carbon monoxide has no smell, so your nose cannot tell you a room is safe.
Rising and sinking
Natural gas is lighter than air, with a relative density of about 0.6, so it tends to rise. LPG vapour is heavier and can collect low down, which is why Great Britain's 1998 Regulations restrict LPG storage and some LPG appliances in cellars and basements.
Standing and working pressure
Standing pressure is measured with no gas flowing; working pressure with appliances running. Pressure drops as gas flows along a pipe. The path teaches what the readings mean, never how to take them.
The lessons this guide comes from
- Natural gas and LPG
- Lighter or heavier than air
- Standing and working pressure
- Gas rate
Keep learning
Sources
Sources checked 29 October 2026. The law and official pages can change.
- Gas Safety (Installation and Use) Regulations 1998, regulation 6Restrictions on LPG storage and appliances below ground in Great Britain.
- HSE: about LPGWhat LPG is and how it is stored.