When the results of a walk-around survey indicate that noise levels may exceed those outlined in the Occupational Noise Exposure standard, additional monitoring is necessary through the sampling of noise exposures from each potentially overexposed job classification. An 80-decibels threshold is used to determine compliance with the 85-decibels time-weighted average action level under OSHA’s noise standard. As a minimum, sampling should be conducted for a length of time necessary to establish whether exposures are above the limits permitted.