AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Standard Test Method for the Measurement of Filtration Efficiency of Electret Facepiece Respirators Challenged with Diesel Exhaust
SWATHI SATISH, Jacob Swanson, David Kittelson, David Y. H. Pui, University of Minnesota
Abstract Number: 563 Working Group: Instrumentation and Methods
Abstract Electret respirators are widely used by workers in underground mines as respiratory protection against exhaust from heavy duty diesel engines. The current NIOSH standard testing procedure for evaluating the filtration efficiency of air-purifying respirators requires using sodium chloride (NaCl) or dioctyl phthalate (DOP) as the test aerosol. This method is not easily adaptable for diesel exhaust as preliminary results show that unlike NaCl and DOP, diesel particulate matter (DPM) has characteristics that depend very nonlinearly on operating and sampling conditions. This poster presents a methodology that enables us to achieve a high degree of control over those properties of DPM that have the potential to significantly impact the measurement of filtration efficiency. By fixing the ratio of elemental carbon (EC) to organic carbon (OC) in the exhaust, the dilution ratio and the residence time, DPM with reasonably well-defined characteristics will be obtained regardless of the diesel engine used to generate exhaust.
Exhaust from a diesel engine is first treated with an over-sized diesel oxidation catalyst (DOC), which oxidizes all of the organic compounds to produce dry black carbon aerosol. Organic carbon in the form of motor oil vapor is injected into the high temperature flow stream. The resulting mixture is diluted with clean dry air to facilitate adsorption and condensation of oil vapors onto the soot particles, forming the required standard test aerosol. The respirator is tested with this aerosol at 85 L/min and its filtration efficiency is determined using mass concentration measurements obtained from laser photometers placed upstream and downstream of the respirator. The significance of the proposed method lies in the concept of creating DPM with a unique set of properties according to the requirements of its application.