The story
From Initialism of Not resistant to oil particles with 99% filtration efficiency in NIOSH air filtration ratings.
Etymology from Wiktionary, CC BY-SA 4.0.
N99
Today it means: N99 standard Full definition →
Today it means: N99 standard Full definition →
From Initialism of Not resistant to oil particles with 99% filtration efficiency in NIOSH air filtration ratings.
Etymology from Wiktionary, CC BY-SA 4.0.