Survival of bacterial and mould spores in air filter media.

The survival of bacterial and mould spores in new and used air filter media is explored. Samples of different media were challenged with specific microbial aerosols in a filtration test unit, and the viability of the microorganisms collected in the filter media examined. In five days there was no noticeable decrease or increase in the viability, nor did relative humidity have an influence. In two new filter media the viability declined notably at high relative humidity, a trend attributed to the combined effect of spore rehydration and diffusion of fibre substances in the spore which rendered them prone to air flow and air toxics. Abundant mould growth occurred in static conditions in a climatic chamber in two filter media. States that the results indicate that atmospheric dust deposited in air filters may serve as nutrient for moulds if the humidity is sufficient and filters are not exposed to an air flow.