Technical aspects of gaseous formaldehyde as a sterilant

The design of a sterilizer for sterilization of heat sensitive items using gaseous formaldehyde and steam is described. The sterilizer is able to create a constant formaldehyde-steam concentration over a period of at least one hour. It is further able to operate at formaldehyde concentrations close to saturation with only small residues on sterilized plastic materials. The autoclave is used for measurement of formaldehyde solubility in polyolefines and poly(vinyl chloride) being approx. 15 and 250 ppm, respectively, at 70 degrees C and 30 mg HCHO I-1. The diffusion coefficient of formaldehyde in poly(vinyl chloride) is measured and is in the same order of magnitude as for ethylene oxide in poly(methyl methacrylate) i.e. 10(-10) cm2 s-1. Measurements of airborne formaldehyde in front of different sterilizers show that it is possible to design facilities meeting occupational exposure limits.