A device for controlling relative humidity in an environment with a solidified humectant composition. The solidified humectant composition is made from a humectant salt, water, and a carrier. The solidified humectant may be formed into a tablet with the aid of a binder, or it may be contained within a thermoformed felt material, a sachet, or a water permeable canister. In a preferred embodiment, the sachet is made of a micro-perforated polyester/paper/polyethylene material. Preferred humectant salts include CaCl2, K2CO3, LiCl, NaCl, K2SO4, and combinations thereof. A preferred embodiment of the present invention includes the use of one or more of: an antimicrobial agent, activated carbon, a volatile organic, a moisture adsorber and an oxygen absorber, in combination with the solidified humectant salt.