OSHA's interpretation is stringent: only one day of noise exposure in excess of 85 dBA time-weighted average triggers inclusion in the hearing conservation program. But hearing loss prevention, like any other safety and health program, is not just a regulatory matter. For practical reasons and best practice, many companies provide protections to employees with only occasional noise exposures, as well as temporary workers and contractors. For more information, see NIOSH's webpage and OSHA's topic page.