The employer and its workers’ compensation insurer appeal from a decision of the Department of Industrial Accidents reviewing board (board) affirming the decision of an administrative judge. The board awarded the employee double compensation pursuant to G. L. c. 152, § 28, finding that the employee’s injury was due to the serious and wilful misconduct of the employer.1 We reverse.

Background. We summarize the facts found by the administra-*39live judge and adopted by the board.2 On Valentine’s Day, 1991, the employee was working at a floral shop operated by the employer when she fell into an unguarded trap-door floor opening and tumbled to the floor below, sustaining serious injuries. The floor door, which covered a set of stairs leading down to the cellar, measured approximately eight feet by three feet. The floor door, when open, reveals what is not disputed to be a “floor opening” subject to the safeguards outlined in Massachusetts and Federal regulations.3

The employer relied upon a warning system of orange safety cones and chains to direct the employees’ attention to the potential hazard and preclude the likelihood that anyone would fall into the opening when the door was open.4 The workers, including the employee who had worked at the shop for five years, were aware of the floor door. The Occupational Safety and Health Administration had inspected the workplace in the early 1980’s without commenting on the floor door, although recommending exit signs and fire extinguishers.5 No other employee had ever sustained an injury related to the fact that the door was sometimes open during work hours.

There was conflicting testimony whether there was sufficient floor space between the open floor door and a table set against the wall where completed orders were placed; while ordinarily *40the space was sufficient, on Valentine’s Day, a very busy day in the flower industry, the circumstances were not ordinary in that the pace was much brisker.

The employer’s enforcement of the warning system was inconsistent, and the cones and chains were not in place at the time of the employee’s accident. In any event they would not have physically prevented a person from falling into the opening. The judge found that the employee’s injury was causally connected to the lack of safeguards when the door was open.

The administrative judge initially refused to admit the regulations into evidence and denied the employee’s § 28 claim. However, after appeal to the board, the case was recommitted to the judge for admission and consideration of the regulations.6 The judge then admitted the regulations and allowed the § 28 claim. The board affirmed. On appeal, the employer and insurer argue that (i) the judge and board improperly relied solely upon the regulatory violation when allowing the employee’s claim,7 (ii) the finding that the employer engaged in serious and wilful misconduct was an error of law, as the regulatory violation was not shown to be intentional, and (iii) the evidence was insufficient as a matter of law to support the finding of serious and wilful misconduct.

Discussion. We may set aside or modify the decision of the board, pursuant to G. L. c. 152, § 12(2), if the decision is, among other reasons, “[bjased upon an error of law” or “[arbitrary or capricious, an abuse of discretion, or otherwise not in accordance with law.” G. L. c. 30A, § 14(7)(a)-(d), (/), (g), as appearing in St. 1973, c. 1114, § 3.8

*41The judge found that, by failing to install the required railings and instead sporadically enforcing its own warning system, the employer engaged in serious and wilful misconduct, see G. L. c. 152, § 28. “The ‘serious and wilful misconduct’ which lays the foundation for double compensation under § 28 of the [workers’ compensation] act ‘is much more than mere negligence, or even than gross or culpable negligence. It involves conduct of a quasi criminal nature, the intentional doing of something either with the knowledge that it is likely to result in serious injury or with a wanton and reckless disregard of its probable consequences.’ ” O’Leary’s Case, 367 Mass. 108, 115 (1975), quoting from Scaia’s Case, 320 Mass. 432, 433-434 (1946). “[N]ot only must the actor intentionally do the act upon which he is sought to be charged, but also he must know or have reason to know . . . facts ‘which would lead a reasonable man to realize that the actor’s conduct not only creates an unreasonable risk of bodily harm to the other but also involves a high degree of probability that substantial harm will result to him.” O’Leary’s Case, 367 Mass. at 116, quoting from Scaia’s Case, 320 Mass. at 434, and citing Restatement (Second) of Torts § 500 (1965). See Moss’s Case, 451 Mass. 704, 713-714 (2008).

We conclude that the record before us does not support a determination that the employer’s conduct attained a wanton and reckless disregard for safety that was quasi criminal in nature; our cases and those of the Supreme Judicial Court in which § 28 liability was upheld have required conduct of a significantly greater magnitude than that shown here. Armstrong’s Case, 19 Mass. App. Ct. 147 (1984), is instmctive, involving a worksite where falling debris was a regular feature, and the employee, like three other workers before him, had refused to undertake work at a specific location because of the danger. At the foreman’s order, however, the employee eventually complied, resulting in his permanent and total disability from falling timber. Id. at 149-150. Similarly, O’Leary’s Case, supra, involved a deliberate order by a foreman to disregard an important safety provision, forcing an employee to work on steel beams having sharp steel protrusions called shear connectors, in violation of the collective bargaining *42agreement. 367 Mass. at 116-117. In Memmolo’s Case, 17 Mass. App. Ct. 407 (1984), an employee was injured after the employer ignored a regulation requiring him to notify public utilities before conducting ground excavations, and a supervisor ordered the employee to continue digging despite the appearance of underground concrete. Id. at 409, 412. Finally, in Paccia’s Case, 4 Mass. App. Ct. 830 (1976), a foreman ordered an employee to work in a trench that had not been shored up, contrary both to instructions from the general foreman and to regulations. Id. at 830. In sum, the deliberate disregard of a known safety requirement in the face of admonitions to the contrary is a prevalent theme of these cases.9

By contrast, the failure, identical to that in Paccia’s Case, to shore up a trench in violation of applicable regulations, but in circumstances lacking the admonition or contrary instruction, was found not to constitute serious and wilful misconduct. Lopes’s Case, 277 Mass. 581, 584-585 (1931). Other cases in which the employer’s conduct was held insufficient to support doubled penalties under § 28 are analogous to this one, or involve conduct that was arguably worse. For example, the failure, again in violation of regulations, to have installed a safety guard on a carding machine, Sciola’s Case, 236 Mass. 407, 414 (1920), and the employer’s refusal of a suggestion to use “tested,” rather than ordinary, chains on the dryer roll of a paper making machine, Scaia’s Case, 320 Mass, at 433-435, were each deemed insufficient under § 28. In the latter decision, the court’s language is equally descriptive of the record in this case: “[Tjhere was evidence that [the employer] could have been more careful and that he took some risk in using the ordinary chain, but we fail to find evidence that the risk he took was both so obvious and so great as to render his conduct ‘serious and wilful,’ that is, practically speaking, wanton and reckless, within the established construction of section 28.” Id. at 435.

The employer’s precautions were inadequate and the enforcement of those precautions was, in the event, ineffective. This *43conduct can certainly be characterized as negligence or gross negligence. But our cases do not support a determination that the employer acted with wanton and reckless disregard for the consequences or engaged in behavior that was quasi criminal in nature. The reviewing board’s decision was arbitrary and capricious in the sense of not having adequate evidentiary and factual support. See Moss’s Case, 451 Mass, at 712.

Decision of the reviewing board reversed.