| (3) Pollution control equipment and machinery or equipment used in processing, packing, or marketing by an original producer, may qualify even if the machinery and equipment are affixed to real property. For a timber producer to qualify for sales tax refunds or credits on qualifying items that are installed under a contract to improve real property, the timber producer must enter into a separated contract. Additionally, the contract must separately state the charges for the qualifying items from the charges for other tangible personal property. See §3.291 of this title (relating to Contractors) for information regarding new construction contracts. See §3.357 of this title (relating to Nonresidential Real Property Repair, Remodeling, and Restoration; Real Property Maintenance) for information regarding nonresidential real property repair, remodeling, or restoration. (j) Repeal of previous exemption. Effective October 1, 2001, the exemption in Tax Code, §151.3161, that took effect on October 1, 1995, is repealed. That provision allowed a tax exemption for the first $50,000 of the purchase price of each complete unit of machinery or equipment used exclusively in a commercial timber operation to prepare the site, plant, cultivate, or to harvest timber in the regular course of business.