Yes, yes, yes, they do. Those little pink hippo guys really are thirsty and suck in the excess moisture in the air. I’ve tested them in my own most scientific way- one closet with and one closet without the dehumidifier for one year (replaced the dehumidifiers twice)- the books in the one without the dehumidifier was visibly more yellowish. The books also smelled less musty and there was no powdery white mold residue that you often see when things get left unattended for a few weeks.
Now here’s the thing though- those thirsty hippo dehumidifiers are made of silica gel and need to be replaced quite often which can amount to quite a bit. I’ve tried using the ones that you can dry out in the sun but they’re nowhere near as good. So the only thing really (apart from airing your entire place everyday, closets and all) is to get an electrical humidifier, and if you’ve got a big place, an industrial size (around $150-600) one is the best.
And it’s not just the tropical isles that have this problem actually. Northern climes where homes have basements also have humidity issues as the lower grounds tend to be more damp, especially where there is little to no air circulation. So best check out basement dehumidifiers for sale if your walls feel damp or things stored are getting that dull moldy powdery white look. It’s an investment worth making, not just to keep your stuff from degrading faster but also for your health.
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. They do work. My basement is now a very pleasant place after placing a dehumidifier: no smell of humidity, no leaks from walls, no spoilt furniture and crinkly books. I have even placed a Billiard table there, so my children spend much time there. It proved to be very useful.