Who leads the tenancy tribunal when the chair is unavailable?

This answer concerns Ontario’s Residential Tenancies Act, 2006, which governs the residential tenancy tribunal identified in the question. The Lieutenant Governor in Council appoints one Board member as Chair and one or more members as vice-chairs [cite:ca-ontario-rta-2006-sec170]. If the Chair is absent or unable to act, the Chair may designate one of the vice-chairs to act. That person then exercises the powers and performs the duties of the Chair [cite:ca-ontario-rta-2006-sec170]. Accordingly, the person leading the hearing is not simply an arbitrary board member: it is the vice-chair designated by the Chair for the Chair’s absence or inability to act. The statutory language concerning a vice-chair who “shall exercise the powers and perform the duties of the Chair” supports treating the acting vice-chair as having the Chair’s authority to conduct the proceeding and participate in the Board’s decision-making while serving in that capacity [cite:ca-ontario-rta-2006-sec170]. The Board itself consists of members appointed by the Lieutenant Governor in Council [cite:ca-ontario-rta-2006-sec169], but the Act does not authorize any member to take over merely because that member is available. The replacement mechanism specifically depends on the Chair’s designation of a vice-chair [cite:ca-ontario-rta-2006-sec170].