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What is a Humidity Absorber?

By S. Mithra
Updated May 17, 2024
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No one likes when lingering moisture causes mildew, mold, or encourages musty odors. A humidity absorber is a chemical, usually enclosed in a packet or bucket, which can be placed indoors to lower humidity. It reduces the water vapor in the air by turning a crystallized substance into a liquid gel that permanently traps water molecules. Many rooms in a house, vehicle, or business would benefit from the improvement in dampness due to a humidity absorber.

A humidity absorber placed in a damp or humid area will prevent mold from forming on books, furniture, or other household items. Mold can be damaging to objects, but also dangerous to sufferers of allergies or asthma. Some places appropriate for a humidity absorber are in cars, boats, recreational vehicles, underneath sinks, couches, or in closets, lockers, or cabinets. Even if your home has a central dehumidifier appliance, these enclosed spaces often do not have enough air circulation for it to be effective.

Most types of humidity absorbers use special chemical granules that are hygroscopic, which means they attract and absorb water floating in the atmosphere. These crystals must be in an appropriate container that has pores to let in water, yet funnels the liquefied gel into a reservoir so it can't drip out. Some containers resemble boxes with lids punched full of holes and two compartments inside, a top one for crystals and a bottom section for gel. They're often reusable by refilling them with more granules.

Other types are bags or pouches that can be hung over closet rods or adhered to walls. Their plastic lining is permeable to entering moisture, but doesn't allow anything to leak out. Some varieties, designed for closets, are reusable blocks of material that you can dry out in a warm oven after they change color as an indication that they are full.

A humidity absorber will not only eliminate excess moisture, but unwanted stale or musty odors. Look for one with a fresh scent like orange, lavender, or jasmine. There are also non-scented varieties. The humidity absorber is completely non-toxic, so it is safe for use in children's play areas or near pets' litter boxes and food bowls. Some kinds can absorb as much as three times their weight in water. Once all of the crystals have transformed into gel, the liquid can be thrown away with your regular garbage.

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Discussion Comments
By anon353073 — On Oct 28, 2013

Yes, I agree with you. Moisture causes mildew, mold, or has a terrible smell and can be really dangerous to the health. I have used a mini moisture trap for smaller spaces such as bathrooms and utilities and it has worked very well.

By LisaLou — On Jun 02, 2012

I always keep a humidity absorber somewhere on my boat. There always seems to be water somewhere and this helps keep it dry and smelling nice.

Some of them have more of a pleasant smell than others, and it is much nicer to smell this than just the scent of stale moisture.

I use this all year long and have had good results. When I store my boat for the winter, it helps keep the area fresh and clean smelling. When I take my boat out of storage in the spring, it no longer has such a stale odor to it.

I can see where something like this might work better in a small, enclosed area. I am going to try using this under my sink and see if it helps keep that area drier and smelling better.

By sunshined — On Jun 02, 2012

@anamur - I agree that the price of using a humidity absorber seems high. It didn't seem so high when I first bought it, but it seemed like it had to be replaced frequently. I might not have minded so much if I felt like it was doing a good job, but I didn't notice much of a difference.

I used this in my basement which always seems to be damp and have musty smell to it. I usually run a dehumidifier down there as well, but was looking for something else that would help take away the odor.

I have gone back to just using the dehumidifier as I feel it is cheaper and works just as well. Maybe moisture absorbers would work better in a smaller space than a big open space like my basement.

By bear78 — On Jun 01, 2012

I'm still kind of confused about how a humidity absorber works. And how can it be completely non-toxic?

For some reason, when I think of a humidity absorber, the silica gel packets that come with newly purchased items come to mind. Those absorb moisture too, but they're poisonous. That's why it always has a warning to keep it away from children and pets.

What's the difference between the desiccant silica used in silica packets and the substance used in humidity absorbers?

By serenesurface — On May 31, 2012

@burcidi-- I'm mostly pleased with how these things work too, but don't you think they're too expensive? There refills are almost the same price as a whole unit including the tablet and they are extremely difficult to find.

I was really happy with it the first time I used a humidity absorbent. But after buying it for the third time, I feel it's too costly and it's also not enough for large rooms. I find that it works the best for small, enclosed spaces, especially closets and wardrobes. But if you put it in, say the living room, it doesn't make as much of a difference. Especially considering how fast it runs out.

I'm not sure if I'm going to keep buying them. I wish they were made more efficient and more affordable.

By burcidi — On May 31, 2012

@mlayne-- That's a good question. I'm not sure, but I've been using one for the past three weeks in my bedroom and I have not felt that there is less oxygen than before.

I don't have a mold problem in my room but it always smelled musty. Since it doesn't get as much light as the rest of the house, it always cold and damp in there. So I decided to get a moisture absorber to see if it would make a difference.

They had a large size available for larger rooms and a small one for smaller rooms. I got a small one and after three weeks, the tablet that came with is only half gone. But it has collected a considerable amount of moisture! I'm actually really surprised. I knew my room was damp, but when you see the collected water in the container, it's different.

By mlayne — On Mar 17, 2011

are the oxygen or hydrogen molecules damaged in any way during this process? Could the potential hydrogen energy still be contained.

By anon75377 — On Apr 06, 2010

where can I obtain the "reuseable" blocks?

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