21. Challenge procedure
(1) The parties are free to agree on a procedure for challenging an arbitrator.
(2) In the absence of such agreement, a party who intends to challenge an arbitrator shall, within 30 days after becoming aware of the constitution of the arbitral tribunal or after becoming aware of any circumstance referred to in section 20(2), send a written statement of the reasons for the challenge to the arbitral tribunal. Unless the challenged arbitrator withdraws from his office or the other party agrees to the challenge, the arbitral institution administering the arbitration or, where there is no such institution, the Court shall decide on the challenge. While such a request to the arbitral institution administering the arbitration or, where there is no such institution, to the Court, is pending, the arbitral tribunal may continue the arbitral proceedings and make an award.