Electrostatic Charge Decay in Synthetic Filter Media

Both the electrostatic factor and the decay constant are fitted quantities and neither transfers between media — they must be recovered from measured penetration on the specific product, ideally by testing charged and discharged samples of the same batch. The single exponential also hides that charge decays through several mechanisms at once, with the surface component going far faster than the bulk. Oil aerosols and organic vapours neutralise electret charge in service on a timescale of hours, which is a separate and usually more urgent problem than shelf ageing. Respirator performance is a certified safety matter — this models a degradation mechanism and is not a fitness-for-use determination.