Use of Particle Counters To Identify Contaminant Sources In Buildings

Tenants of a mixed-use office suite reported several unexplained health effects that were purportedly associated with building occupancy.  These effects include headache, respiratory problems, eye irritation, and discomfort associated with unpleasant tastes and odors.  The structure was previously affected by water damage from interior flooding.  The building tenants therefore suspected that ailments could somehow be linked to mold contamination related to the flooding event.

Study Design
This case study involved a 11,000 sq. ft. facility containing office space, warehouse, and a small-scale metal machining area.  We reviewed reports and remediation plans related to the earlier water damage.  The distribution of water damage was found to be highly localized.  Furthermore, the scope of building repairs was more than adequate given the type of flooding and its distribution.  Assessment of the building enclosure showed no evidence of moisture-related problems that might account for concealed mold within exterior walls.

Our initial building walkthrough revealed that the machining room shared ceiling plenums and supply air distribution systems with offices, common areas, and warehouse.  Although the two high-speed milling machines were operated within enclosures under independent air exhaust, containment was incomplete and mill wastes were freely exposed to the common atmosphere.  Milling was therefore suspected as the primary contaminant source and the likely cause of reported ailments.  To test this hypothesis, we performed real-time monitoring of airborne particles at 27 locations during operating and non-operating conditions.   Settled dust samples from represented surfaces, including the supply air distribution system, were analyzed for unknown material identification by means of polarized light microscopy, epi-reflected light microscopy, Scanning Electron Microscopy (SEM), energy-dispersive X-Ray spectrometry (EDX), and Attenuated Total Reflection Fourier Transform Infrared Spectrometry (ATR-FTIR).

Our findings indicated that milling operations, not mold, represented the most likely source of airborne particles.  Because the milling process was poorly contained, particles were capable of cross-contaminating other areas of the building by means of ambient air movement and cross contamination of supply air ducts.  Concentrations were highest in areas that shared the same supply air (milling area, conference room, and reception area).  Airborne particles in the machining room were extremely high during pre-milling periods and increased more than two-fold while the milling machines were operating.   Unknown materials identifications of settled dust revealed high levels of fine metal particles and various compounds consistent with metalworking oils and fluids.   Concentrations of biological particles were deemed normal.

 Particle Counters and Indoor Air Quality

Hand-held particle counters can provide a reliable, cost-effective means for monitoring and trouble-shooting suspected air quality concerns.  In this case, monitoring provided a useful indicator of airborne contaminant source and probable pathways for occupant exposure.