Woman with severe allergy ‘left with no choice’ but to buy every packet of peanuts on flight
(www.independent.co.uk)
As in, removing 99,97% of particles over 0.3 micron in size.
HEPA filters remove 99.97% of particles that are 0.3 micron in size. (That is the size of particles they're tested with, as it's the most difficult to filter.) They remove over 99.97% of particles larger or smaller than 0.3 microns.