Some of my comments are tongue firmly-in-cheek.
However, regarding fire extinguishers - One can purchase small single-use FEs now, app 2.5” in diameter and about 8” high, about the size of a can of spray paint, with a finger-pull trigger. And a holster. Could come in handy for runners, etc.
The fire extinguisher as a defense for dog attacks I presume was discovered by firemen who needed to get into a burning building, or were being attacked while attempting to give aid. It may work up to three ways - the powder or foam as a surprise, the sound which resembles a snake, or most important - spraying the nose and mouth to render the dog unable to breath without letting go of its victim. There do exist vids of firemen driving off dogs with FEs.
And as for the small personal FEs upon which I just commented, I now wonder if spray-paint or aerosol hairspray would function in the same manner.
I would rather carry a dog extinguisher.
It also serves as a bad guy extinguisher.
As well as a bear extinguisher.