What's the difference between P95, P100 and OV cartridges?

P95 filters at least 95% of airborne particles; P100 (sometimes labeled HEPA) filters at least 99.97%, including oil-based aerosols. OV (organic vapor) cartridges absorb solvent fumes from paint, finishes, adhesives and pesticides. For spray painting you typically want a combined OV + particulate cartridge; for sanding or woodworking, a P100 particulate filter is the gold standard cited across the reviewers we read.