The particle capture of an electret filter is contributed by both mechanical and electrostatic capture mechanisms. An electrostatic capture mechanism significantly improves the quality factor (filtration performance per a unit resistance); and when the surface charges are decayed, filtration mostly depends on the mechanical capture of particles. It is well accepted that IPA treatment removes the surface charges of filter media; therefore, the IPA-treated samples can be deemed as the mechanical filter (mechanical contribution noted as “mech. cont’n”) (Figure 2 and Figure 3B). The performance above this level of filtration for the untreated respirators A and B is considered as the electrostatic capture mechanism (electr. cont’n). Disinfection treatments such as solvent immersion, UV, oven-dry, and microwaving seemed to have negligible impacts on the structural integrity (Figures S3 and S4); accordingly, there were no apparent changes in the resistance and mechanical filtration after those treatments. Notable fiber damage was found in the laundered samples by the external force imposed during laundering (Figure S3A). The physical damage of Resp. A resulted in the decrease of resistance and mechanical filtration performance, corresponding to the lower filtration efficiency compared with Resp. B.