Except as provided in subsection (b) of this section, whenever an employer has an employee working in a manhole, the employer shall have another employee available in the immediate vicinity of the manhole to give emergency help. The employee who is available to give emergency help may enter the manhole to give other help. For a brief period, a qualified employee who is working alone may enter a manhole where cables or equipment are in service to: perform an inspection; perform housekeeping; take readings; or do other work if it can be performed safely.