Does the standard require employers to count any day during which an employee is required to use a respirator, for any amount of time, as a day of respirator use for purposes of applying the 30-day trigger for medical surveillance?

Yes. If an employee is required by the standard to use a respirator at any time during a given day, regardless of the duration of the respirator use, that day counts as one day toward the 30-day threshold for medical surveillance. Thus, a “day” of respirator use for purposes of the 30-day threshold does not mean a full day of respirator use.