The article describes investigations on brown spots sometimes found on silver photographic images and caused by contaminated atmospheres. Two test methods are described. Use of a zinc sulfide paper moistened with water or with aqueous ammonia indicated the solubility properties of the silver compounds constituting these spots, and with other observations showed the chemistry of their production to be ill-defined and complex. Test strips containing yellow colloidal silver (grain size > 30 nm) were found to be darkened by dangerous atmospheres much more rapidly than photographic images were damaged, and are produced by Agfa-Gevaert AG. These strips showed that particular sources of damaging contamination were certain types of plastic index cards and automobile exhaust gases, among others. A restoration method for damaged negatives is described; it consists of soaking the negative for a controlled time in a 0.5-1. 0% solution of iodine in alcohol, followed by fixing and washing.