I agree with PaulaO2 that you're probably smelling the hose, but it may also be the humidifier container.
I would also follow the recommendation of using only vinegar and water (or in my case, a germicide like Control III) in a total immersion/soak for several hours followed by a good rinse and dry-out before initial use, not for cleaning so much as to get rid of the "eau de plastique" perfume :-), vs. any form of soap, shampoo or detergent.
Many years ago, a food manufacturing specialist told me that if one is not careful, the residues from consumer-grade cleaning products can actually encourage mold growth [yuck!] - knowing how life can throw distractions your way (meaning I'm rushed and don't rinse properly), I use Control III...
You may find that gentle scrubbing of hose interior with an appropriately-sized brush may also help....
Finally, for normal hose cleaning/soaking, a number of vendors [e.g. Amazon,
[link removed] Supplier #1, etc] sell this little hanging pale blue hose rack with end caps. It IS a bit flimsy, but it does allow total soaking of a hose's interior with only the liquid required to fill the hose vs. filling a bucket with cleaning solution etc..
Hope this helps...
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