CDPH Lead Inspector/Assessor California State Practice Exam

What is the recommended number of calibration check readings for an XRF instrument before an inspection?

1. One nominal-time reading

2. A set of three readings

3. Five consecutive readings

4. Two readings taken at different intervals

The correct answer is: A set of three readings

The recommended practice for calibrating an XRF (X-ray fluorescence) instrument before an inspection involves taking a set of three readings. This approach ensures that the calibration of the instrument is accurate and reliable. By obtaining multiple readings, you can assess whether the instrument consistently measures the same values and identify any potential errors or deviations in its performance. Taking three readings allows for a better statistical evaluation of the calibration process, which increases confidence in the results that will be obtained during the actual inspection. A single reading would not provide enough data to verify accuracy, and while five consecutive readings could offer more information, they may not be necessary for ensuring calibration. Similarly, two readings taken at different intervals may not provide comprehensive coverage of the instrument's performance, which is vital for accurate lead content analysis. Thus, three readings represent a balance between thoroughness and efficiency in the calibration process prior to an inspection.