The story
From Initialism of oil-Proof with 100% filtration efficiency in NIOSH air filtration ratings.
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: P100 standard Full definition →
From Initialism of oil-Proof with 100% filtration efficiency in NIOSH air filtration ratings.
Etymology from Wiktionary, CC BY-SA 4.0.