I must take exception, as I imagine other conservators will, with the statement that calcium chloride is not a risk to collections. It has been found to pose a significant risk when used in proximity to collections museum collections. Calcium chloride strongly attracts water molecules in the air and solubilizes rapidly to form ionic solutions – even at a microscopic level. one of its purposes in industry is to create microscopic surfaces that stay continuously wet and conductive – road salt as the prime example. Ionic solutions are HIGHLY reactive – initiating corrosion in metals, hydrolyzation in skins, leathers, feathers and other protein materials such as gelatin photographic emulsions, denaturating chemical dyes in costumes, textiles and documents . It is also highly abrasive as a fine powder. The desiccant satchels containing commercially available calcium chloride are designed to be generally permeable to water molecules but fine enough to prohibit large quantities of calcium chloride out. That said, the crystals inside the satchels continually break down in to finer and finer particles and will escape as dust particles of the size that suspend easily in room-air convection currents. Where ever convection currents slow – on and under shelving or within cabinets or drawers, these particles settle on whatever material is sitting on those shelves. Where they settle, they immediately initiate accelerated chemical reactions that damage many collection material surfaces. This is not a material you will want to use in conjunction with museum material storage.