Patent ID: 8748723

Claim:
A humidity control device for use in a closed environment for maintaining a relative humidity in the closed environment in the general range of 40% to 60%, the device comprising: (a) a pouch formed of a thin-walled polymeric material permeable to water vapor but not to liquid solutions; (b) a humidity control solution comprising saturated aqueous salt solution containing an amount of alkali metal formate selected from sodium formate and potassium formate and combinations thereof sealed in said pouch wherein said salt solution contains from about 30% to 90% salt; and (c) wherein the water vapor permeability of the pouch is such that the moisture transfer capacity of the pouch transmits at least from about 1% to about 50% by weight of the initial pouch contents in a 24-hour period when exposed to an atmosphere of less than 10% relative humidity and absorbs at least from about 1% to about 50% by weight of the initial pouch content when exposed to an atmosphere having greater than 85% relative humidity.