AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Filtration of Combustion Aerosols by Facepiece Respirators and Stationary IAQ Filters
SHUANG GAO, Jin Yong Kim, Michael Yermakov, Xinjian He, Yousef Elmashae, Tiina Reponen, Sergey A. Grinshpun, University of Cincinnati
Abstract Number: 123 Working Group: Control Technology
Abstract Filters used in filtering facepiece respirators (FFR) and in indoor air quality (IAQ) control devices are usually tested with aerosol simulants such as NaCl, KCl, or dioctyl phthalate. It is assumed that these tests produce filter efficiency levels representative of real aerosol hazards, e.g., particulate combustion products. However, little data are available to justify the above assumption. In this study, we tested the samples of two types of filters: one was an N95 FFR filter widely deployed in occupational environments, and the other was a MERV 14 stationary indoor filter used in heating, ventilation and air conditioning (HVAC) systems. Both were challenged with three combustion aerosols (produced by burning wood, paper and plastic) and with a NaCl aerosol. Each tested filter sample was mounted on a specially designed holder. The particle concentrations and size distributions upstream and downstream of the filters were determined by a Nanocheck (Grimm Technologies, Ainring, Germany) in a size range of 15 to 900 nm. Different air flow rates were applied to the filter samples representing typical inhalation conditions for respirators and conventional air exchange rates for IAQ control devices. For both filter types, we observed significant difference (p<0.05) between the total particle penetrations of the tested combustion materials and NaCl particles. The plastic combustion aerosol showed the lowest filtration efficiency, followed by paper, wood, and NaCl. The size-selective analysis indicates that the greatest difference between penetrations of combustion and NaCl particles occurred within a size range of 20–80 nm, and the difference was found dependent on the challenge aerosol, flow rate, and type of the filter. It was concluded that the filter efficiency obtained with a well-established simulant such as NaCl may overestimate the protection level offered by the same filters against combustion aerosols.
This work was supported by NIOSH Contract 200-2013-M-56581.