ARCHIVED REPORTS_ROY'S AUTO - HISTORICAL (2)

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I Y � is attached. However, the decision logic for a sample of units is more complicated than for single residential units, and should be fully grasped before a sample is selected. How to Sample The recommended method for testing in a residential unit at this time is the K shell reading from a portable XRF instrument. Substrate corrections are to be made where necessary. Standard reference material paint films developed by NIST for usage with XRFs are to be used to demonstrate that XRF instruments are in control. XRF results are in units of milligrams per square centimeter. An average of three readings is recommended. Each reading should be approximately 15 seconds with a new source. Appropriate adjustments in reading time should be made for source age. Where portable XRF is not feasible due to a surface being narrow or curved, where greater accuracy is desired, or where comparison to the percent by weight standard is desired, paint samples can be collected and sent for to a laboratory for analysis. The paint samples should be collected from a one square inch area. Care should be taken to collect all the paint in the area, and to minimize the inclusion of substrate material. Lead in paint samples collected in this way can be reported in both milligrams per square centimeter and percent by weight. If a surface is so deteriorated that XRF is not feasible• and a paint sample cannot be collect from a square inch, then a strip of peeling paint is to be collected. Lead from such a sample can only be reported in percent by weight units. How to Analyze Paint Samples Paint chip samples should be analyzed by a laboratory recognized by EPA's National Lead Laboratory Accreditation Program. Paint samples should be no more than 500 milligrams in weight. If the paint samples received by the laboratory are larger than 500 milligrams, the laboratory should homogenize and subsample the paint samples to select a subsample of approximately 500 milligrams for the analysis. Results reported by the laboratory must make the appropriate adjustment for the subsampling. Conclusions For single houses and units, conclusions are reached as follows. XRF results are to be corrected for substrate effects where necessary. Corrected XRF results are divided into three categories: positive, inconclusive, and negative. Reading averages of 1.6 mg/cm2 or more are classified as positive; reading averages or 0.4 mg/cm' or less are classified as negative. All other reading averages are classified as inconclusive. K-shell XRF results in the positive category indicate lead is present at or above 1.0 mg/cmZ. K-shell XRF results in the negative category indicate lead is not present at or above 1.0 mg/cm2. The probability of false positives is currently estimated to be at least less than 10%, and less than 5% in most cases. The 5