Open source hardware and reliable method for measuring air humidity in a room?

Hey everyone,
I’m in the process of moving and need to figure out what kind of things I can store in a cellar without risking damage due to humidity. Anyone know of a good approach to take to figure this out?

Don’t store clothes in there and anything made of cardboard or similar materials.

Plastic containers can seem like a good idea but if there is humidity around they can collect condensation…the best is to have some moisture absorbing products like

If you use absorbing products, you can store most of things really, even wood, but I still wouldn’t store cardboard or anything softer than wood but of same material.

So this category is the open source hardware helpdesk now? I’d like that. :blush:

Like Jasen said, desiccants are great to prevent dampness and mould when storing a wide variety of things in a cellar.

I had similar issues in the truck when not being there for several weeks or even months in winter, and now find a great (and cheap) solution: excessive amounts of calcium chloride (example: 10 kg for 18 EUR). This material is the most frequently used agent in the non-electric room dehumidifiers.

They sell also dehumidifiers for these 1 kg fabric bags, but no need for these (and they are way too expensive for what they do). I’d just use a large enough bucket at the bottom to catch the solution and a plastic or stainless steel kitchen colander places at its top, with the bag in there. So all water it captures will just run into the bucket, and from there can be emptied into the drain. By using a bucket that is large enough, you don’t have to worry that it might overflow while in use; one kilogram calcium chloride will grab up to 7 l of water out of the air over time.

By using excessive amounts of large enough dehumidifier buckets distributed in the room, the room will keep dry for a year or longer.

Caveats: success depends on the type of cellar. If it’s a small room with a tightly closing door, that’s perfect. If the whole cellar is one large open space, it will be difficult to keep that dry by any means. In that case, I’d put sensitive items into airtight boxes, together with silicium dioxide as dehumidifier. That other type of dehumidifier stays completely solid when attracting water, so does not endanger anything in the box by producing some sort of solution.

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For solutions in living quarters you could also have some decorative stuff made of salt, absorbs a lot of water I think