Examination of the physical and chemical nature of used ventilation filters and collected particulate matter

Maintenance workers expressed concern of a potential health hazard due to a strong odor from used ventilation filters during routine maintenance at a research facility. This prompted a thorough examination of the physical and chemical nature of the filters and collected particulate matter. Light and electron microscopy indicated a predominance of opaque small particles, mostly in the submicrometer range. Many were agglomerations of smaller, roughly spherical subunits, consistent with combustion aerosol. Headspace samples of filter portions were analyzed by gas chromatography-mass spectroscopy (GC-MS). Numerous volatile organic compounds were found on all samples at sub-ppm concentrations. Possible odor sources are: combustion aerosol containing adsorbed vapors, organics normally present in ambient environments concentrating on the particles, and/or microbial growth. The combined approach of GC-MS/microscopic examination proved useful in determining the vapor and solid collection history of ventilation filters. The concentrations of toxic substances were below levels at which adverse effects would be expected.