The A, B, C Classification¹

The A, B, C System can be traced back to the oldest CSA standard for hearing protectors published in 1965. Subsequent editions of the Standard have kept it with minor changes. However, the Standard is now under revision, expected to be re-issued in the year 2022. It is

unknown if the CSA Technical Committee on Occupational Hearing Conservation that is presently revising the Standard will keep the system or scrap it altogether.