Iowa Admin. Code r. 875-220.225
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. 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 federal Fair Labor Standards Act, 29 U.S.C. 207(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. Alternatively, 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.
Iowa Admin. Code r. 875-220.225
29 CFR 553.225.