The department, or a laboratory designated by the department which has been certified pursuant to Section 12500.7, shall certify the standards of the county sealers as often as may be deemed by the director to be necessary, based upon a review of statistical data resulting from previous certifications, but in no event shall the period of time between certifications exceed 10 years. In the absence of statistical data, standards shall be certified at least every two years. Sealers shall, upon the request of the department, deliver for testing those standards in their possession which are used in the discharge of their duties. Direct expenses incurred in the certification process shall be borne by the state, while any incidental expense, such as the cost of transportation, shall be borne by the county whose standards have been certified.