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Lead Paint Inspection
What is it?
A surface-by-surface investigation to determine the presence or absence of lead-based paint and a certified report of the results.
Most Common Inspection Method
Portable XRF lead-based paint analyzers are the most common primary analytical method for inspections in housing because of the demonstrated ability to determine if lead-based paint is present on many surfaces and to measure the paint without destructive sampling or paint removal, as well as the high speed and low cost per sample. Portable XRF instruments expose a building component to electromagnetic radiation in the form of X-rays or gamma radiation. In response to radiation, each element, including lead, emits energy at a fixed and characteristic level. Emission of characteristic x-rays is called “X-Ray Fluorescence,” or XRF. The energy released is measured by the instrument’s fluorescence detector and displayed. The inspector must then compare this displayed value (reading) with the threshold or inconclusive range specified in the XRF Performance Characteristic Sheet (PCS) for the specific XRF instrument being used, and the specific substrate beneath the painted surface (see section IV.F, below). For instrument – substrate combinations that have a threshold:
✦ If the reading is less than the threshold, then the reading is considered negative for lead-based paint.
✦ If the reading is greater than or equal to the threshold, then the reading is considered positive.
For instrument – substrate combinations that have an inconclusive range:
✦ If the reading is less than the lower boundary of the inconclusive range, then the reading is considered negative.
✦ If the reading is within the inconclusive range, including its boundary values, then the reading is considered inconclusive.
✦ If the reading is greater than the upper boundary of the inconclusive range, then the reading is considered positive.
As of the publication, the detection elements and software of all of the XRF analyzers for which HUD has issued PCSs, all of the inconclusive ranges and/or thresholds are based on 1.0 mg/cm2, so that positive and negative readings are consistent with the HUD definition of lead-based paint for identification and disclosure purposes. Laboratory analysis is recommended to confirm inconclusive XRF results, as mentioned in Section I.G, below; alternatively, the paint can be presumed to be lead-based paint.
XRF Performance Characteristic Sheets and Manufacturer’s Instructions
When an XRF instrument is used for testing paint in target housing or pre-1978 child-occupied facilities, it must have a HUD -issued XRF Performance Characteristic Sheet. XRFs must be used in accordance with the manufacturer’s instructions and the PCS.The PCS contains information about XRF readings taken on specific substrates, calibration check tolerances, interpretation of XRF readings, and other aspects of the model’s performance.
If discrepancies exist among the PCS, the HUD Guidelines and the manufacturer’s instructions, the most stringent guidelines should be followed. For example, if the PCS has a lower (more stringent) calibration check tolerance than the manufacturer’s instructions, the PCS should be followed.
These Guidelines and the PCS are applicable to all XRF instruments that detect K X rays, L X rays, or both. Most XRF instruments in use at the time of publication of this detect K-shell fluorescence (X-ray energy), some instruments, L-shell fluorescence, and some, both K and L fluorescence. In general, L X rays released from greater depths of paint are less likely to reach the surface than are K X rays, which makes detection of lead in deeper paint layers by L X rays alone more difficult. However, L X rays are less likely to be influenced by substrate effects.