5 C.F.R. § 551.215
(c) Engaged in fire protection activities.
(1) An employee (including a firefighter, paramedic, emergency medical technician, rescue worker, ambulance personnel, or hazardous materials worker) is considered engaged in fire protection activities for the purpose of determining possible application of section 7(k) of the Act as provided for in § 551.501(a)(1) and (5) and § 551.541 if the employee:
(2) Subject to the requirements of paragraph (c)(1) of this section, the following types of employees are engaged in fire protection activities for the purpose of determining possible application of section 7(k) of the Act:
(d) Not engaged in fire protection activities. Examples of types of employees who are not engaged in fire protection activities for the purpose of applying section 7(k) of the Act (as provided for in § 551.501(a)(1) and (5) and § 551.541) include the following:
(4) Employees on rescue and ambulance crews who: