The biggest problem is that folks think 5-10% will do fine on dogs and humans when 20-40% is what was used on bears.
First off, the bears are not used to being attacked by humans; some dogs and humans are. Thus the surprise factor is missing.
Second, bears have a LOT of mucous membrane hanging out there; mouthes open, big watery eyes with exposed mucousy underlids, and BIG wet noses. Also bears in particular and dogs on occassion, are breathing a lot during an attack.
People have very little mucous membrane to hit. They are not usually breathing heavily during an attack, and they are more capable of overcoming something with some sort of thinking.
As to Mace... HAH. Thirty years ago, when I was a military cop, a friend of mine, a silly county cop, came up and sprayed me with a can of MACE which we'd been told to rely on. I quickly pulled mine out and used the entire can on him through the open window of his car. Ten minutes later, out in 30 degree weather, we were smoking cigarettes together and agreeing that we would NEVER spray someone with MACE unless we already had them cuffed and under the gun.. Later on, I got a dose of MACE on a hot, humid summer day and found it to be far more uncomfortable. However I was NOT messed up so much that I could not have done something terminal to someone if I had to.
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