Fresh air bases in mines require emergency staffing and rescue equipment before entry beyond the base is permitted. Fresh air bases in mines must be set up in fresh air as near as possible to the irrespirable zone, with telephone connection where practicable. Rescue trained persons may not proceed beyond the base until specified personnel and emergency equipment are provided, unless delay would endanger life. If persons are already working beyond the base, the same persons, apparatus and equipment must be supplied there as soon as possible.