A man uses a lighter to relight the Olympic torch held by torchbearer and former swimming champion Shavarsh Karapetyan (L), after the flame was blown out during Karapetyan’s ran through the Kremlin in ...

For a flame to be sustained, three things need to be present: fuel, oxygen (or an alternative oxidising agent) and heat. This is known as the triangle of combustion, and if any of the three sides of ...