I actually used one of those 30+ years ago when there was a big fire that burned many, many acres around Black River Falls, WI. Our group had the task of walking around putting out hotspots with those cans strapped to our backs. Known by all that use them as, pardon the expression, "piss cans". It was a dirty, dirty job and made more uncomfortable if you were one of the lucky ones that had a can that leaked down your back, pants, and boots all day.