Measuring airflow through the portable high-efficiency air filtration (PHEAF) device to assess reliability of instrument and sample location.

The portable high-efficiency air filtration (PHEAF) device is an engineering control common to the environmental remediation industry. Damage to the high-efficiency particulate air (HEPA) filter (e.g., filtration media, gasket), improper installation of the filter into the mounting frame, or defects in the filtration housing affect the capture efficiency of the device. PHEAF devices operating at less than marketed efficiencies justify periodic leak testing of the PHEAF device, especially when the filtered air is exhausted into occupied spaces. A leak test is accomplished by injecting a known concentration of aerosol upstream of the HEPA filter and measuring the percentage of aerosol penetrating through the filtration system. The test protocol scripted for stationary systems (i.e., biological safety cabinets) states that upstream concentrations can be empirically determined using the aerosol photometer to measure particulate matter (PM) in the airstream. This practice requires a homogenous mixture of the aerosol challenge agent within the airstream. However, design of the PHEAF device does not include a validated induction point for the aerosol. Absent of an acceptable means to achieve a homogenous mixture for upstream measurement, the aerosol concentration is mathematically derived based on the measured air volume passing through the PHEAF equipment. In this study, intake volume and exhaust volume for each PHEAF device were measured by either the balometer or the hot wire anemometer. Variability of measurements was examined by instrument and sample location (intake vs. exhaust) to understand which combination would be most consistent for measuring airflow volume. From this study, the authors conclude that the balometer is preferred compared with the hot wire anemometer for measuring airflow through the PHEAF device. Exhaust measurement by balometer seems more reliable than intake measurements by hot wire anemometer. Implications: Although testing of PHEAF devices is recommended by various public health authorities, no nationally recognized test protocol has been published in the United States. In support of measuring the performance of the PHEAF device in a field setting, this study evaluated the hot wire anemometer and balometer techniques and sample locations (intake vs. exhaust) to reliably measure airflow through the PHEAF device. Since accuracy of the particle measurement is associated with airflow volume, it is essential to obtain a true airflow reading. This study suggests that the balometer was more consistent in measuring airflow through the PHEAF device.

Capture efficiency of portable high-efficiency air filtration devices used during building construction activities.

The portable high-efficiency air filtration (PHEAF) device is used to control particulate matter (PM) generated from construction-type activities occurring within the built environment. Examples of activities where PHEAF devices are mobilized include building renovation, asbestos abatement, remediation of microbial contamination, and lead-based paint projects. Designed for use on short-term, temporary projects the PHEAF device captures airborne PM using a high-efficiency particulate air (HEPA) filter. This study sought to evaluate the capture efficiency of the PHEAF device in a field setting. An aerosol generator and photometer were used to measure particle penetration through 85 PHEAF devices. Average overall capture efficiency ranged from 41.78% to ≥99.97% with more than 88% of the tests failing to achieve 99.97% capture efficiency. Approximately 73% of the PHEAF device sample population failed to demonstrate HEPA performance criteria during any test round. A higher occurrence of PM concentrations measured around the perimeter of the filter suggested the presence of bypass leakage. While PHEAF devices were effective in capturing a significant quantity of aerosol test agent, these findings suggest that routine testing of the PHEAF device should be conducted to validate performance.

A multi-laboratory comparative study of spore trap analyses.

Fungal spore trap analyses currently are being marketed to the medical and environmental industries as a means of evaluating fungal bioaerosols. No studies comparing the results of these analyses have been conducted among laboratories providing these services. In the current study we compared the results from seven such laboratories with four different commercial spore trap cassettes with samples from four environmental conditions. The conditions included indoor air from a single location in a building under low, moderate and high agitation, and a sample from outside the same building. The means, ranges and standard deviations of total spore counts per cubic meter were respectively: low agitation indoor 514, 40-1933, 395; moderate agitation indoor 446, 80-1120, 290; high agitation indoor, 5154, 1510-15278, 3335; and outdoor 16012, 3700-28959, 6600. Results were similarly variable for the 27 spore categories that contribute to the total count. No consistent difference was observed in the precision of the kinds of spore traps. We concluded that spore trap analyses should be used with caution and should not be used as a sole method of assessing fungal spore populations and that standardized methods of analysis must be developed that include information about analytical precision of the sample data.