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.