On review of the record we detect no error or evidence of bias in the hearing examiner’s actions and decision. After a one-day hearing in which documentary evidence comprising, as here, approximately twenty-eight exhibits, some with multiple parts, and covering the history of a contentious tenant-landlord relationship over a four and one half year period, it is not surprising that a hearing examiner, upon review, should conclude there may be missing elements in the evidence. Faced with the regulatory imperative that “[tjhere *223shall be a full and fair open proceeding to determine whether . . . a certificate of eviction [shall be] issued” (under the board’s regulation 35-01), it was not an abuse of discretion for the hearing examiner to provide a complete and comprehensive record. Analogous regulatory systems promote hearing officer amplification of the record in the interests of completeness and fairness. See 801 Code Mass. Regs. § 1.02( 10)(g)(5)(1993)10; 20 C.F.R. § 404.944 (1993).11 The dictates of fairness were well preserved by the hearing examiner’s offer, after supplementing the record, to receive further documentation, argument, or requests for a further hearing. He did not rely on secret evidence. There was no violation of the general principle that “[w]hatever actually plays a part in the decision should be known to the parties and subject to being controverted.” Schwartz, Administrative Law § 7.13, at 369 (2d ed. 1984). To the extent the hearing examiner’s activities constituted outside consultation, he acted within the spirit of the board’s regulation 36-04,12 which permits such consultation outside the hearing provided the parties are given an opportunity to participate. Here, the hearing examiner issued a clear invitation to participate. Cf. New York Central R.R. v. Department of Pub. Works, 354 Mass. 332, 336 (1968). Norway Cafe, Inc. v. Alcoholic Bevs. Control Commn., 7 Mass. App. Ct. 37 (1979).