Advanced testing method to evaluate the performance of respirator filter media

ABSTRACT

Filter media for respirator applications are typically exposed to the cyclic flow condition, which is different from the constant flow condition adopted in filter testing standards. To understand the real performance of respirator filter media in the field it is required to investigate the penetration of particles through respirator filters under cyclic flow conditions representing breathing flow patterns of human beings. This article reports a new testing method for studying the individual effect of breathing frequency (BF) and peak inhalation flow rate (PIFR) on the particle penetration through respirator filter media. The new method includes the use of DMA (Differential Mobility Analyzer)-classified particles having the most penetrating particle size, MPPS (at the constant flowrate of equivalent mean inhalation flow rate, MIFR) as test aerosol. Two condensation particle counters (CPCs) are applied to measure the particle concentrations at the upstream and downstream of test filter media at the same time. Given the 10 Hz sampling time of CPCs, close-to-instantaneous particle penetration could be measured. A pilot study was performed to demonstrate the new testing method. It is found that the effect of BF on the particle penetration of test respirator filter media is of importance at all the tested peak inhalation flow rates (PIFRs), which is different from those reported in the previous work.

KEYWORDS:

• Breathing frequency
• cyclic flow
• inhalation flow rate
• particulate matter (PM)
• respirator filter media

Additional information

Funding

Qiang Wang and Da-Ren Chen appreciate the partial financial support from Center of Filtration Research, University of Minnesota. The members of the Center consists of 3M, BASF, Boeing, Cummins Filtration, Donaldson, Entegris, Ford Research & Innovation Center, W. L. Gore & Associates, H.B. Fuller, MANN+HUMMEL GMBH, MSP, Samsung Electronics, Shigematsu Works Co., Ltd, TSI Inc., XinXiang Shengda, and Guangxi WatYuan Filtration System Co., Ltd.