D.C. Mun. Regs. tit. 10, r. 10-C3104
A majority of the duly constituted Board shall constitute a quorum for the purpose of conducting business at a public hearing or meeting pursuant to these regulations.
If the Board loses a quorum during the course of a meeting, unless otherwise prohibited, the Board may at its own discretion proceed to conduct business without a quorum on a case-by-case basis, provided that there is no objection from the applicant or any person interested in the matter under consideration by the Board.
Actions of the Board shall be taken in public by a majority vote among the members present and voting, and the vote of each member shall be recorded and noted for inclusion in the transcript or minutes of the meeting.
A member may participate and vote on a case even though that member may not have attended prior proceedings in the case, provided that the member has reviewed the complete record in the case.
D.C. Mun. Regs. tit. 10, r. 10-C3104