North by Honeywell air purifying respirators with filters provide respiratory protection against aerosols by removing dusts, mists, fumes, fibers, and other particles. Filters do not remove gases or vapors, or correct for oxygen deficiency. End of service life for filters is normally determined by the increase in breathing resistance sensed by the user. When it becomes difficult to breathe comfortably, the filters should be replaced. R95 filters are limited to a maximum of 8 hours use, when used in atmospheres containing oil. 2 per dispenser. p100 filters may be used in atmospheres containing oil-based aerosols.