Anti microbial materials and coatings are rather expensive and would eventually be a hazard if they corroded or disolved into the water meant to evaporate.

Mold and bacteria thrive in moist, humid environments. It’s less that humidifiers have been engineered to need excessive cleaning and more that their intended function encourages this growth as a natural consequence.

Preventing it would require doing things to the water that you probably don’t want to do to something you’re intending to aerosolize and inhale, or else treating the device itself in ways that are likely to require cleaning and/or maintenance anyway.

So at that point it’s cheaper and safer just to tell people they need to clean their humidifiers because the thing that makes humidifiers good for you also makes it good for stuff you don’t want building up in the humidifier.

Mold is life. Life grows where there is water. Humidifiers dump tons of water in their general vicinity. It's a natural consequence of humidifiers.

As noted by the other person there are ways to get around it by making the humidifier itself out of materials that kill anything that it touches, but those materials are almost never safe.

Copper would probably be the least concerning from a health standpoint, but copper is not cheap, and it's really heavy.

It's way more practical to just ask you to scrub it every once in a while.

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it has to be cleaned???

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