Meltblown Pore Size & Filtration Pressure Drop Modeler

Pressure drop is given two ways. The Davies figure is his 1953 correlation as published, computed from the solidity and fibre diameter above with no fitted constant; he built it on media with fibres far coarser than meltblown. Refitted to six N95 filtering layers with fibres of about 2.5 µm, the same correlation needed its leading constant cut from 64 to 8.3 (O Shaughnessy and others, Journal of Occupational and Environmental Hygiene, 2023), so the recalibrated figure is the closer guide for fine meltblown and the Davies figure an upper estimate. The recalibrated resistance constant is that figure in the form the Filter Media Efficiency, Resistance and Quality Factor tool takes, so the two tools agree when it is carried across. Pressure drop is mechanical only; it says nothing about the electret charge that carries most of the efficiency in respirator media, and charge decays. Respiratory protection is decision-support only — certification requires testing to the applicable standard.