May I suggest changing your list container class to:
public class EquipmentNeedingService : List<Equipment>
{
// no internal list is need: public readonly List<Equipment> ...();
// no need to any AddEquipmentToList(), but if you insist:
public void AddEquipmentToList(Equipment equipment)
{
this.Add(equipment);
}
}
Later you can easily enumerate EquipmentNeedingService
just like any list.