MICROBIAL-GROWTH ON RESPIRATOR FILTERS FROM IMPROPER STORAGE

Microbiological contamination and particle penetration were studied in two respirator filters with high efficiency. Microbial growth in filt er materials during storage under humid conditions and the passing of microorganisms through the filters were particularly examined. Filters with different fiberglass and cellulose proportions were loaded in en vironments containing high microbial levels and incubated at a relativ e humidity of 98%. Particle penetration through loaded and incubated f ilters and carbon, nitrogen and microbial content were measured. After incubation, considerable particle penetration and the passing of fung al spores were observed for filters composed mainly of cellulose, prob ably because of humid conditions, which stimulated fungi to grow and e xtend mycelia and spores through the filter. Microbial activity, micro organism concentrations, and the chemical properties of the filter mat erials also supported this hypothesis. Storing used respirators in hum id environments may result in heavy microbial contamination of the fil ters, especially if the filter material is biodegradable by microorgan isms.