1911.16—Powers of presiding officer.
         The officer presiding at a hearing shall have all the powers necessary or appropriate to conduct a fair and full hearing, including the powers:
    
    
    
    
        
        (c) 
         To confine the presentations to the issues specified in the notice of  hearing, or, where no issues are specified, to matters pertinent to the proposed rule;
    
    
    
    
        
        (f) 
         To take official notice of material facts not appearing in the evidence in the record, so long as parties are entitled, on timely request, to an opportunity to show the contrary; and
    
    
        
        (g) 
         In his discretion, to keep the record open for a reasonable, stated time to receive written recommendations, and supporting reasons, and additional data, views, and arguments from any person who has participated in the oral proceeding.