How?
Discussion
https://www.computerhardwareinc.com/2022/01/19/beware-the-bulging-battery-and-what-to-do-if-yours-expands/ | https://archive.ph/3c68a
I have a swollen battery in an old iPhone, the original first generation, or maybe second generation (iPhone 3G). I don't know really, but I know mine is swollen, and years old. Realized it's buried in the clutter here somewhere. Ordered myself a fire extinguisher from Amazon to have nearby. Just in case.
old iPhone hasn't exploded yet.
Fire extinguisher expected to arrive tomorrow.