Breathing boards have the hygroscopic capacity to keep room humidity in a range from 40% to 70%. When the humidity of room air rises, the vermiculite absorbs extra moisture, and when the humidity of room air goes lower, the vermiculite releases the moisture they have absorbed. Breathing boards can control room humidity and offer a comfortable hospital environment by capturing harmful substances which volatilize from building materials, furniture, etc. and are considered to cause sick building syndrome. They have the ability to prevent the propagation of bacteria.