Conformance has been used as a correctness criterion for asynchronous circuits. In the case of untimed systems, conformance of an implementation to a specification is equivalent to the failure-freeness between the implementation and the mirror of the specification. For bounded-delay systems, in general this property does not hold. In this paper, we define various notions of failures and examine whether the above property holds or not. We then discuss an alternative and effective algorithm for conformance checking of bounded-delay asynchronous circuits.