100. FACILITIES Each utility shall, unless specifically excused by the Commission, provide such laboratory, meter testing equipment and other equipment and facilities as may be necessary to make tests required o it by these rules or other orders of the Commission. The apparatus and equipment so provided shall be subject to the approval of the Commission, and it shall be available at all times during business hours for inspection or use on the premises of the utility by any authorized representative of the Commission.105. TESTS REQUIRED Each utility shall make such tests as are prescribed under these rules with such frequency and in such manner and at such places as are herein provided, as may be approved or ordered by the Commission. Unless otherwise directed by the Commission, the methods and apparatus recommended by the National Bureau of Standards shall be used.110. METER PROVERa. Each utility furnishing metered gas service shall own an approved type of meter prover, preferably of not less than five (5) cubic feet capacity, equipped with suitable thermometers and other necessary accessories, and it shall maintain such equipment in proper adjustment so that it shall be capable of determining the accuracy of any service meter to within one-half of one per cent. Each meter prover shall be so placed that it will not be subject to drafts or excessive temperature variations.b. The accuracy of all provers and methods of operating them shall be established by the utility subject to approval and changes from time to time by a representative of the Commission, All alterations, accidents or repairs which might affect the accuracy of any meter prover or the method of operating it shall be promptly reported in writing to the Commission.