R99

noun

R99 standard

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Meanings

nounR99 (countable and uncountable, plural R99s)

plural R99s

  1. R99; Ellipsis of NIOSH R99.
    1. uncountableR99 standard
    2. countableR99 filter

Origin

From Initialism of Resistant to oil particles with 99% filtration efficiency in NIOSH air filtration ratings.

Full word history & related roots →
Cite this entry
APA

R99. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/R99

MLA

“R99.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/R99. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “R99,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/R99.

Source: R99 on Wiktionary, CC BY-SA 4.0.