The LPA-1 Lead Paint Analyzer is a state-of-the-art XRF spectrum analyzing system for the quantitative measurement of lead in paint on various substrates. The LPA-1 Analyzer provides a fast, accurate measurement of lead content in 1 to 5 seconds, thereby assuring the highest level of productivity for an inspector.
The advance design of the LPA-1 represents a new generation of XRF system. By employing technological advances in the fields of electronics and microprocessors, and combining them with knowledge gained from experience with existing x-ray fluorescence technologies, the new analyzer can now make accurate assessments of lead levels in a fraction of the time previously needed. The result is the most effective lead inspection system available today.
The LPA-1 method of measurement is based on spectrometric analysis of lead K-shell x-ray fluorescence in a controlled depth of paint. Unlike L-shell x-rays, K-shell x-rays can easily go through the paint without being affected by different thickness and composition of various layers of paint that can cause false readings. The controlled depth concept used in the design of the LPA-1 restricts the penetration of the energetic K-shell x-rays into the substrate so that the system cannot be mislead by the presence of lead pipes or other objects located deep in a wall.
The LPA-1 uses a Co-57 radioactive source and a modern solid state x-ray detector to generate a spectrum of the fluorescence from the painted surface. The spectrum is then analyzed by a microprocessor to eliminate the effects of scattering and other factors such as the influence of the substrate to allow an accurate determination of the amount of concentration of lead on the surface to be made.
The LPA-1 microprocessor can analyze spectrometric data in real time and can pick out the lead signal from the spectrum much faster than can be done by eye. The built in permanent memory (ROM) of the analyzer provides the storage for the radiation coefficients and mathematical formulas used for substrate correction and calculation of the lead content. The microprocessor also controls the unit self-calibration and monitors all other aspects of system operation.
The most intriguing aspect of the LPA-1 analyzer is its ability to make a variable time measurement with a 95% confidence level (2 sigma) based on the regulation action level. This approach is consistent with the proposed ASTM method of measuring lead in paint. This method of analysis is a new concept that utilizes the advance circuitry of the LPA-1 and provides the inspectors the highest level of productivity by optimizing the time required to achieve a statistically meaningful measurement.
There are two measurement modes of operation in LPA-1 analyzer namely the “Standard Mode” and the “Quick Mode”. In the “Standard Mode”, the most similar to other lead measuring instruments, the operator selects a fixed measurement time which remains constant irrespective of the lead signal. In the “Quick Mode”, the analyzer automatically adjusts the measurement time to be the least time that is needed to make a definitive measurement with a 95% confidence level (2 sigma). The LPA-1 analyzer will finish a measurement once the 2-sigma confidence level is achieved and the data is statistically meaningful. This time period for conclusive measurements is typically between 1 to 5 seconds depending on the action level.
For example, if the action level had been set to 1.0 mg/cm2 and the actual lead level is 5.0 mg/cm2, even a 1 second reading provides enough information for the unit to determine with at least 95% confidence that the lead level is conclusively above the action level. In contrast, if the actual lead level is 1.3 mg/cm2, the unit will automatically extend the time to 10 seconds, which will provide the required 95% confidence level. In the case where the actual lead level is very close to the abatement level, the unit will extend the measurement to a maximum of 60 seconds and indicate whether or not a conclusive measurement has been made. This approach is the most productive measurement method for the elimination of unnecessarily long measurement times.
The LPA-1 analyzer eliminates the need for constant calibration by being a self-calibrating unit. The system consistently monitors its own internal spectrum and makes self-adjustments as necessary. This will save time as the need for carrying a set of standards and performing calibrations in the field is essentially eliminated.