It has been said that you can't start a fire without a spark, but as Hannah and Dara are about to discover, that's not true!

Welcome to the fiery phenomenon of spontaneous combustion, when something can ignite all on its own: no matches, no sparks, no external flame. It happens when certain materials heat themselves up internally through chemical or biological reactions, and if that carried on unchecked and the material gets hot enough, it can eventually ignite itself.

This process can occur in various everyday items such as piles of hay or grass clippings, oily rags and in certain instances lithium batteries; but there are also several useful chemical substances that autoignite when they come into contact with air - as Hannah, Dara and a wary BBC fire officer witness in the studio...

So how can we stop things regularly bursting into flames? How scared should we be about oiling floorboards and our increasingly battery-powered life? And is spontaneous human combustion really a thing? Our investigators are on the case.

To submit your question to the Curious Cases team, please email: curiouscases@bbc.co.uk

Contributors: - Andrea Sella, Professor of inorganic chemistry at University College London - Emanuel ‘Big Manny’ Wallace, former science teacher now a science content creator - Matt Oakley, fire investigations officer at Surrey Fire and Rescue Service - Roger Byard, Emeritus Professor of pathology at the University of Adelaide and a senior specialist forensic pathologist at Forensic Science SA (FSSA)

Producer: Lucy Taylor Executive Producer: Alexandra Feachem

A BBC Studios Production

Borderlands 4 Breaks Records and its own engine | The Best Gaming Podcast # 543