Spontaneous human combustion possible?

This week, we tackle the burning issue of spontaneous human combustion. Is it possible for humans to spontaneously burst into flames and if so, how?

Hannah - Well, bacteria in the human gut naturally produce phosphine gas, methane and hydrogen. Phosphine gas, also known as PH₃ - a phosphorus attached to 3 hydrogens - could feasibly, spontaneously convert to diphosphine P₂H₄. If this happens, it could ignite the methane and hydrogen fuels in the gut and cause an explosion, igniting in our abdomen and providing high temperatures for the burning of the fat on our skin and the clothes on our back. Surely then, this could make spontaneous human combustion a possibility? Over to Dr. John Emsley, chemist and author. He's contributed his considerable spark to the scientific feasibility of such combustion in nature...

John - Spontaneous combustion is seen as a possible explanation for the "Will-o-the-Wisp" phenomenon that was flickering lights that can be seen over marshes at night when something appears to ignite methane as it bubbles to the surface.

Hannah - So, the explosive combination of phosphine gas, diphosphine, methane and hydrogen are emitted by the marsh bacteria that live there, eating the decomposing material - these mix, causing spontaneous combustion and a scientific explanation for the marsh folklore of small goblin-like fairies, mischievously leading travellers off the bitten path at night, using light that looked to be shelter. So, back to microbes living in the human gut, could phosphine gas mix with the hydrogen there to form diphosphine and thereby, ignite the methane? If so, surely, this could explain any reported cases of spontaneous human combustion. Back to John...

John - But it seems highly unlikely, why is that? Well, because getting two phosphorus atoms to bond together in diphosphine requires a lot of energy. They didn't see much point in microbes producing this.

Hannah - So, due to energy requirements, spontaneous human combustion seems improbable. But just to be sure, has diphosphine ever been found lurking in our guts?

John - Diphosphine has never been detected in human intestine or gas.

Hannah - Spontaneous human combustion, at least via this chemical pathway looks to be out of the question though. Thanks, John Emsley for setting us straight. We next turn our attention to this.

Neil - Hi. I'm Neil from Glasgow. I find that I can't work with music playing. All my attention is on the music and it distracts me. On the other hand, I have friends who can't work unless they have music, that loud volume blasting through their skulls via their headphones. Why does this difference exist?

Hannah - Music, a concentration aid or a complete distraction. Find out next time why some people find it helpful and others disruptive...?