(7) (a) "Lead-based paint" shall mean paint or other similar surface coating material containing 1.0 milligrams of lead per square centimeter or greater, as determined by laboratory analysis, or by an x-ray fluorescence analyzer. If an x-ray fluorescence analyzer is used, readings shall be corrected for substrate bias when necessary as specified by the performance characteristic sheets released by the United States environmental protection agency and the United States department of housing and urban development for the specific x-ray fluorescence analyzer used. X-ray fluorescence readings shall be classified as positive, negative or inconclusive in accordance with the United States department of housing and urban development "Guidelines for the Evaluation and Control of Lead-Based Paint Hazards in Housing" (July 2012) and the performance characteristic sheets released by the United States environmental protection agency and the United States department of housing and urban development for the specific x-ray fluorescence analyzer used. X-ray fluorescence readings that fall within the inconclusive zone, as determined by the performance characteristic sheets, shall be confirmed by laboratory analysis of paint chips, results shall be reported in milligrams of lead per square centimeter and the measure of such laboratory analysis shall be definitive. If laboratory analysis is used to determine lead content, results shall be reported in milligrams of lead per square centimeter. Where the surface area of a paint chip sample cannot be accurately measured or if an accurately measured paint chip sample cannot be removed, a laboratory analysis may be reported in percent by weight. In such case, lead-based paint shall mean any paint or other similar surface-coating material