I have been our school librarian, in the same room, for several years. Since August, I have not been able to get the humidity below 55% and the room smells like a musty cellar. Our HVAC guy has been in here twice and recharged one of the units. He says both units now are working, that since we live in a humid state, 55% is pretty good and smells can come from anywhere. He suggested I turn the thermostat down to 68 degrees to get the humidity out. I've tried to explain that it has never felt or smelled like this before. I finally purchased a temp/humidity gauge. At times the humidity has been as high as 72% with the AC keeping the room at 72 degrees. Currently, Classroom next door--75 degrees and 45% humidity. Hallway that doesn't even have vents--75 degrees and 48% humidity. This library--68 degrees and 55% humidity. Part of the time, the humidity goes UP once the AC kicks on in the morning. Humidity in a library is never supposed to go above 50% because it affects the quality of the materials. I would like to stress that this is a NEW phenomenon. It has not been a problem until this year. Thanks for your ideas.