35 Miss. Code R. § 4-07-03-305
Manufacturing machinery does not include machinery for use in the severance of timber, sand, gravel, oil, gas or other natural resources produced or severed from the soil or water, maintenance or repair machinery, research laboratory machinery, storage facilities warehouse machinery, equipment for protection of the plant or comfort of the personnel or other equipment and supplies of like character. Equipment used in the treatment of water by a manufacturer qualifies for the reduced rate of tax. Equipment used in the treatment of water by a public or private water system or sewage system is not classified as manufacturing machinery and does not qualify for the reduced rate of tax. The term "manufacturing machinery" does not include foundations or materials for their construction, nor does it include portable equipment that is not assembled and used at a fixed location.
35 Miss. Code. R. § 4-07-03-305