Air pollution effects on library microforms

Abstract

The use of microfilm for the preservation of the information content of acidic, embrittled books has increased dramatically. Research was undertaken between 1989 and 1993 by the Image Permanence Institute (Rochester, New York) to identify and measure the threat to micrograph materials by common air pollutants. Eight types of microfilm and four other contemporary photographic products were exposed to controlled amounts of ozone (O 3 ), hydrogen sulfide (H 2 S), nitrogen dioxide (NO 2 ), and sulfur dioxide (SO 2 ). Temperature, relative humidity (RH), and gas concentrations were varied and the effects on the image were measured. Two specially constructed chambers were designed to withstand the corrosive atmospheres and allow close control of all variables in the study over a wide range. Results show that photographic materials differ greatly in their response to air pollutants. Some are unaffected even after exposure to high concentrations of pollutants at extremely high temperatures and RH. Others show a particular sensitivity to one gas. At moderately high concentrations (5 ppm), ozone and nitrogen dioxide attack and fade conventional color films at room temperature and RH. Furthermore, image silver in black-and-white film is extremely sensitive to combinations of oxidizing and sulfiding gases, although it is not sensitive to high levels of either oxidants or sulfiding gases on their own.