42 CFR § 84.181 - Communication performance test—PAPR class PAPR100.

(a) Powered air-purifying respirators must be designed to allow for proper communication while worn.

(b) A Modified Rhyme Test 7 will be used to test the wearer's ability to communicate efficiently.

7 The Modified Rhyme Test is used in speech intelligibility experiments. See https://www.nist.gov/ctl/pscr/modified-rhyme-test-audio-library.

(c) The communications requirement is met if the overall performance rating is greater than or equal to 70 percent.