(b) Service of subpoenas.

1. (1) When the ALJ issues a subpoena under this section, the party who requested such subpoena shall serve all other parties with a copy of the subpoena, notice of the names and addresses of the individuals subpoenaed and specify any documents required to be produced.

2. (2) Subpoenas may be served:

   1. (i) By a U.S. Marshal or deputy marshal,
   2. (ii) By any other person who is not less than 18 years of age, or
   3. (iii) By registering and mailing a copy of the subpoena addressed to the person to be served at the last known principal place of business or residence.

3. (3) Proof of service may be made:

   1. (i) By the return of service on the subpoena by the U.S. Marshal or deputy marshal,
   2. (ii) If served by an employee of the Department, by a certificate stating that he personally served the subpoena upon the person named therein,
   3. (iii) If served by another person, by an affidavit of such person stating that he personally served the subpoena upon the person named therein, or
   4. (iv) If service was by registered mail, by an affidavit made by the person mailing the subpoena that it was mailed as provided herein and by the signed return post-office receipt. Where the subpoena is issued on behalf of the Secretary and service is by mail, the return receipt without an affidavit or certificate of mailing shall be sufficient proof of service.
4. (4) In making personal service, the person making service shall leave a copy of the subpoena with the person subpoenaed, or, if such person is not immediately available, with any other responsible person authorized to accept service residing or employed at the place of residence or business of the person subpoenaed.
5. (5) The original of the subpoena, bearing or accompanied by the required proof of service, shall be returned to the official who issued the same. The party at whose request the subpoena is issued shall be responsible for the service thereof.