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Niton XLp 300, 9/24/2004, ed. 1 <br /> BACKGROUND INFORMATION <br /> EVALUATION DATA SOURCE AND DATE: <br /> This sheet is supplemental information to be used in conjunction with Chapter 7 of the HUD Guidelines for <br /> the Evaluation and Control of Lead-Based Paint Hazards in Housing ("HUD Guidelines"). Performance <br /> parameters shown on this sheet are calculated from the EPA/HUD evaluation using archived building <br /> components. Testing was conducted in August 2004 on 133 testing combinations. The instruments that <br /> were used to perform the testing had new sources; one instrument's was installed in November 2003 with <br /> 40 mCi initial strength,and the other's was installed June 2004 with 40 mCi initial strength. <br /> OPERATING PARAMETERS: <br /> Performance parameters shown in this sheet are applicable only when properly operating the instrument <br /> using the manufacturer's instructions and procedures described in Chapter 7 of the HUD Guidelines. <br /> SUBSTRATE CORRECTION VALUE COMPUTATION: <br /> Substrate correction is not needed for brick, concrete, drywall, metal, plaster or wood when using Lead-in- <br /> Paint K+L variable reading time mode, the normal operating mode for these instruments. If substrate <br /> correction is desired, refer to Chapter 7 of the HUD Guidelines for guidance on correcting XRF results for <br /> substrate bias. <br /> EVALUATING THE QUALITY OF XRF TESTING: <br /> Randomly select ten testing combinations for retesting from each house or from two randomly selected <br /> units in multifamily housing. Use the K+L variable time mode readings. <br /> Conduct XRF retesting at the ten testing combinations selected for retesting. <br /> Determine if the XRF testing in the units or house passed or failed the test by applying the steps below. <br /> Compute the Retest Tolerance Limit by the following steps: <br /> Determine XRF results for the original and retest XRF readings. Do not correct the <br /> original or retest results for substrate bias. In single-family housing a result is defined as <br /> the average of three readings. In multifamily housing, a result is a single reading. <br /> Therefore, there will be ten original and ten retest XRF results for each house or for the <br /> two selected units. <br /> Calculate the average of the original XRF result and retest XRF result for each <br /> testing combination. <br /> Square the average for each testing combination. <br /> Add the ten squared averages together. Call this quantity C. <br /> Multiply the number C by 0.0072. Call this quantity D. <br /> Add the number 0.032 to D. Call this quantity E. <br /> Take the square root of E. Call this quantity F. <br /> Multiply F by 1.645. The result is the Retest Tolerance Limit. <br /> Compute the average of all ten original XRF results. <br /> Compute the average of all ten re-test XRF results. <br /> Find the absolute difference of the two averages. <br /> 2of3 <br />