5 CFR § 1201.42 - Disqualifying a judge.
(b) A party may file a motion asking the judge to withdraw on the basis of personal bias or other disqualification. This motion must be filed as soon as the party has reason to believe there is a basis for disqualification. The reasons for the request must be set out in an affidavit or sworn statement under 28 U.S.C. 1746. (See appendix IV.)
(c) If the judge denies the motion, the party requesting withdrawal may request certification of the issue to the Board as an interlocutory appeal under § 1201.91 of this part. Failure to request certification is considered a waiver of the request for withdrawal.