40 g Silica Gel Dehumidifier

First off, the cubic volume of your storage area is 392 cubic feet. Each individual canister is designed to cover a maximum of 3 cubic feet. The best option would be to use the smaller canister in each individual box that you are storing in the unit. If you are wanting to use silica gel to cover the entire volume of the storage unit you would need 5,227 grams(or 11.52 lbs), so I would suggest going with a higher volume canister to get the appropriate coverage for your area.

Yes. This product is suggested for use in containers up to 3 cubic feet.

Great question. I don't think it will directly protect it by preferentially attracting the water to itself rather than the CaCl2. I think I would try storing your ice melt wrapped as effectively as you can, and then put it into a container with a small excess volume and protect that volume with either silica gel or more ice melt with a little collection bin, like the ones available at the dollar store. This way, you can try to keep the small volume of air in the container very dry before any significant moisture gets past the bag or plastic bucket that the ice melt is in. Does that make sense?

Yes thought for this amount of Silica Gel (40 grams) it would best be utilized in a space of 3 cubic feet or less.

Not really. You would have to make sure the trailer was air tight so the outside humidity would not be able to enter the trailer. You also need to know the cubic feet of the inside of the trailer. The is a specified amount of silica gel recommended for the amount of space it would be used in.

This product has the following dimensions: 4 depth x 2 height x .5 width in inches.