29 CFR §790.8

1. (a)An employer's liabilities and obligations under the Fair Labor Standards Act with respect to the “principal” activities his employees are employed to perform are not changed in any way by section 4 of the Portal Act, and time devoted to such activities must be taken into account in computing hours worked to the same extent as it would if the Portal Act had not been enacted. 53 But before it can be determined whether an activity is “preliminary or postliminary to (the) principal activity or activities” which the employee is employed to perform, it is generally necessary to determine what are such “principal” activities. 54
2. (b)The term “principal activities” includes all activities which are an integral part of a principal activity. 61 Two examples of what is meant by an integral part of a principal activity are found in the Report of the Judiciary Committee of the Senate on the Portal-to-Portal Bill. 62 They are the following:
   1. (1)In connection with the operation of a lathe an employee will frequently at the commencement of his workday oil, grease or clean his machine, or install a new cutting tool. Such activities are an integral part of the principal activity, and are included within such term.
   2. (2)In the case of a garment worker in a textile mill, who is required to report 30 minutes before other employees report to commence their principal activities, and who during such 30 minutes distributes clothing or parts of clothing at the work-benches of other employees and gets machines in readiness for operation by other employees, such activities are among the principal activities of such employee.
3. (c)Among the activities included as an integral part of a principal activity are those closely related activities which are indispensable to its performance. 64 If an employee in a chemical plant, for example, cannot perform his principal activities without putting on certain clothes, 65 changing clothes on the employer's premises at the beginning and end of the workday would be an integral part of the employee's principal activity. 66 On the other hand, if changing clothes is merely a convenience to the employee and not directly related to his principal activities, it would be considered as a “preliminary” or “postliminary” activity rather than a principal part of the activity. 67 However, activities such as checking in and out and waiting in line to do so would not ordinarily be regarded as integral parts of the principal activity or activities. 67