An exemption from the requirement of a tolerance is established for residues of the 1-Methylcyclopropene in or on fruits and vegetables when:
    
    
        
        (a) 
         Used as a post harvest plant growth regulator, i.e., for the purpose of inhibiting the effects of ethylene.
     
    
        
        (b) 
         Applied or used outdoors for pre-harvest treatments.
     
    
        
            Code of Federal Regulations
        
        [73 FR 19150, Apr. 9, 2008]