FUNGAL COLONIZATION OF AIR FILTERS FOR USE IN HEATING, VENTILATING, AND AIR-CONDITIONING (HVAC) SYSTEMS

New and used cellulosic air filters for HVAC systems including those t reated with antimicrobials were suspended in vessels with a range of r elative humidities (55-99%) and containing non-sterile potting soil wh ich stimulates fungal growth. Most filters yielded fungi prior to susp ension in the chambers but only two of 14 nontreated filters demonstra ted fungal colonization following use in HVAC systems. Filters treated with antimicrobials, particularly a phosphated amine complex, demonst rated markedly less fungal colonization than nontreated filters. In co mparison with nontreated cellulosic filters, fungal colonization of an timicrobial-treated cellulosic filters was selective and delayed.