There are two major sources of respirator leakage: filter and faceseal. What is astm f3502 in this context? The elastic ear loop on many BFCs does not provide adequate seal on the face. OSHA assigns the half-mask respirator with an APF of 10. If means that if the faceseal (tight fitting elastomeric facepiece) has a leakage of 10%, the filter penetration cannot be more than 1%. For the BFC, The elastic ear loop on many BFCs does provide a tight seal on the face. The potential faceseal leakage could be more than 20%. What is astm f3502? Look for a manufacturer like Puraka. For a Level 2 high performance BFC, the total leakage to the submicrometer aerosol can be as high as 70% (50 + 20). Is it acceptable for the users who wear it for protection against submicrometer aerosols? 5. What is the difference in filter efficiency between the charged and neutralized testing aerosol for the BFC test? Do we really need neutralized testing aerosol for the low performance BFC?