R99

noun

noun ·Rare ·Advanced level

Definitions

Noun
  1. 1
    R99; Ellipsis of NIOSH R99.; R99 standard uncountable
  2. 2
    R99; Ellipsis of NIOSH R99.; R99 filter countable

Etymology

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

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.