(a) A judge shall disqualify himself/herself whenever in his/her opinion it is improper for him/her to preside at the proceedings.

(b) At any time following appointment of the judge and before the filing of the decision, any party may request the judge to withdraw on grounds of personal bias or prejudice either against it or in favor of any adverse party, by promptly filing with him/her an affidavit setting forth in detail the alleged grounds for disqualification.

(c) If, in the opinion of the judge, the affidavit referred to in paragraph (b) of this section is filed with due diligence and is sufficient on its face, the judge shall promptly disqualify himself/herself.

(d) If the judge does not disqualify himself/herself, he/she shall so rule upon the record, stating the grounds for his/her ruling. Then, he/she shall proceed with the hearing, or, if the hearing has closed, he/she shall proceed with the issuance of the decision.