It is a common practice among employees engaged in fire protection
activities to relieve employees on the previous shift prior to the
scheduled starting time. Such early relief time may occur pursuant to
employee agreement, either expressed or implied. This practice will not
have the effect of increasing the number of compensable hours of work
for employees employed under section 7(k) where it is voluntary on the
part of the employees and does not result, over a period of time, in
their failure to receive proper compensation for all hours actually
worked. On the other hand, if the practice is required by the employer,
the time involved must be added to the employee's tour of duty and
treated as compensable hours of work.