For the purpose of enforcing this part, carriers engaged in commerce, and persons receiving hazardous substances in commerce or holding such hazardous substances so received, shall, upon the request of an officer or employee duly designated by the commissioner, permit such officer or employee at reasonable times, to have access to and to copy all records showing the movement in commerce of any such hazardous substances, or the holding of the hazardous substances during or after such movement, and the quantity, shipper, and consignee of the hazardous substances, and it is unlawful for any such carrier or person to fail to permit such access to and copying of any record so requested when such request is accompanied by a statement in writing specifying the nature or kind of such hazardous substance to which such request relates; provided, that evidence obtained under this section shall not be used in a criminal prosecution of the person from whom obtained; and provided further, that carriers shall not be subject to the other provisions of this part by reason of their receipt, carriage, holding, or delivery of hazardous substances in the usual course of business as carriers.