(a) In lieu of testing according to § 211.206-1, manufacturers may use the latest available test data obtained according to ANSI STD Z24.22-1957 or ANSI STD S3.19-1974 to determine the mean attenuation and standard deviation for each test frequency and the NRR calculated from those values. Manufacturers whose data is based on the ANSI STD Z24.22-1957 measurement procedure must state in the supporting information required by § 211.204-4 that the mean attenuation and standard deviation values used to calculate the NRR are based on ANSI STD Z24.22-1957.

(b) Manufacturers who initially use available data based on ANSI STD Z24.22-1957 must retest within one year of the effective date of this regulation (by September 27, 1981) the affected categories of hearing protectors in accordance with § 211.206-1 of the regulation, and must relabel those categories as necessary.

(c) Manufacturers who use available data based on ANSI STD S3.19-1974 are not required to retest the affected categories of hearing protectors.

(d) If a manufacturer has both ANSI STD S3.19-1974 test data and ANSI STD Z24.22-1957 test data on a hearing protector category, that manufacturer must use the data obtained according to ANSI STD S3.19-1974.