The department is authorized to conduct examinations, inspections, and investigations for the purposes of this chapter through officers and employees of the department or through any health officer or employee of the state of North Dakota. For purposes of enforcement of this chapter, officers or employees duly designated by the department upon presenting appropriate credentials to the owner, operator, or agent in charge are authorized to enter, at reasonable     times, any factory, warehouse, or establishment in which hazardous substances are held or to enter any vehicle being used to transport or hold such hazardous substances and to inspect and sample at reasonable times, within reasonable limits, and in a reasonable manner finished hazardous substances in retail packages and labeling thereon in such factory, warehouse, establishment, or vehicle. Each such inspection must be commenced and completed with reasonable promptness.