[flignats]

nope, Mark Rober did a video on this. It's urine and sweat.

[kortilla]

nope, had a pool at my house in California that I never peed in and wouldn’t use sweaty. Distinct chlorine smell.

[coldtea]

We can also just drop some drops of chlorine in a bucket of clear water. It smells.

Not sure what the vlogger was exactly testing. Perhaps the "left them sit for 3 days" part, had the chlorine he put dissipate into the air and lose the smell?