Abstract
Polydisperse dioctyl phthalate (DOP) aerosols are employed for testing filter penetration with loading of R- and P-series particulate filters for National Institute for Occupational Safety and Health (NIOSH) certification. Penetration for filters must not exceed NIOSH allowed maximum levels during the entire loading of 200 mg DOP indicating no filter degradation. Degradation of respirators loaded with DOP by other aerosols as well as respirators exposed to both oil and non-oil aerosols found in some workplaces is not well studied. To better understand the degradation of respirators with electrostatic filter media, two models of N95 and P100 filtering facepiece respirators (FFRs) were loaded with polydisperse DOP aerosols up to 200 mg as employed for NIOSH certification testing with simultaneous measurement of filter penetration. In parallel experiments, both N95 and P100 FFRs were loaded with 10 to 200 mg DOP and challenged with polydisperse NaCl aerosol employed for NIOSH certification testing as well as monodisperse NaCl aerosol, and filter penetration was measured. Results showed that filter penetration for both N95 models increased with increasing amounts of DOP loading and exceeded NIOSH allowed maximum penetration (5%) by both DOP and NaCl aerosols indicating filter degradation. Monodisperse NaCl aerosols (20–400 nm) gradually increased the penetration and shifted the most penetrating particle size from ~40 nm to larger sizes. In the case of P100 FFRs, DOP aerosol penetration was below 0.03% for up to 200 mg DOP loading as required for NIOSH certification. Interestingly, one of the two P100 FFR models loaded with 10–50 mg DOP showed >0.03% penetration with polydisperse, as well as monodisperse, NaCl aerosol testing. Overall, the results obtained in the study indicate that some P100 models loaded with DOP at lower amounts may show higher penetration with other aerosols such as NaCl. Further studies are needed to better understand the filter degradation of DOP loaded respirators.