Application by disinfectors for approval will be made on forms furnished by the commissioner. The commissioner may approve or disapprove an application after inspection and recommendation of a full-time State or Federal veterinarian which findings and recommendations shall be based upon the adequacy of the equipment to be used in the application of said disinfectants and the ability and qualifications of the applicant in the usage of said equipment, and said findings and recommendations shall be made only after said veterinarian has inspected such equipment and observed the applicant's operation thereof. Limited approval may be granted to a responsible individual employed by a livestock auction for the disinfection of the premises at which he is regularly employed. Approval may be withdrawn at any time upon evidence of noncompliance with regulations or instructions of the commissioner.