For decades a Gas Mask was part of my uniform worn low below my left hip or under my left arm. When riding having a small waist pack in the same position is unobtrusive. That's just me. Ha, I still find myself reaching for my Canteen when thirsty. And yes, getting to the point of thirst, is a bad, bad, bad...
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No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)