The Commission shall grant, in whole or in part, or deny any petition under section
553
(e) of title
5 requesting the Commission to initiate a rulemaking, within a reasonable time after the date on which such petition is filed. The Commission shall state the reasons for granting or denying such petition. The Commission may not deny any such petition on the basis of a voluntary standard unless the voluntary standard is in existence at the time of the denial of the petition, the Commission has determined that the voluntary standard is likely to result in the elimination or adequate reduction of the risk of injury identified in the petition, and it is likely that there will be substantial compliance with the standard.