Any affected employer may apply to the commission for a rule or order for a variance from a standard or regulation promulgated under this article. Affected employees shall be given notice of each such application and an opportunity to participate in a hearing. The commission shall issue such rule or order if it determines on the record, after opportunity for an inspection where appropriate and a hearing before the commission that the proponent of the variance has demonstrated by a preponderance of the evidence that the conditions, practices, means, methods, operations or processes used or proposed to be used by an employer will provide employment and places of employment to his employees which are as safe and healthful as those which would prevail if he complied with the standard or regulation. The rule or order so issued shall prescribe the conditions the employer must maintain, the practices, means, methods, operations and processes which he must adopt and utilize to the extent they differ from the standard or regulation in question. Such a rule or order may be modified or revoked upon application by an employer, employees or by the commission on its own motion, in the manner prescribed for its issuance under this section at any time after six months from its issuance.