N.C. Gen. Stat. § 99B-3

(1) No manufacturer or seller of a product shall be held liable in any product liability action where a proximate cause of the personal injury, death, or damage to property was either an alteration or modification of the product by a party other than the manufacturer or seller, which alteration or modification occurred after the product left the control of such manufacturer or such seller unless: The alteration or modification was in accordance with the instructions or specifications of such manufacturer or such seller; or

(2) The alteration or modification was made with the express consent of such manufacturer or such seller.

(3) For the purposes of this section, alteration or modification includes changes in the design, formula, function, or use of the product from that originally designed, tested, or intended by the manufacturer. It includes failure to observe routine care and maintenance, but does not include ordinary wear and tear.