from their homepage :

A Fireproof Casing which REALLY Works!

Scared of battery fires? I know that we are!

This is why our Infinite Battery comes with a casing that we designed to resist the heat of a fire, thanks to it's thick aluminum casing, and a design which dissipates heat quickly.

And YES THIS WORKS! We have put a massive effort in making our casing sustain the battery fire, and extensively tested it (videos coming soon), so you can sleep safely (and us too!!). See our complete fireproof testing on our documentation/FAQ