In a TEM clearance z-test, how many samples inside containment, outside containment, and blanks are required, including sealed blanks?

• A. 5 inside containment, 5 outside, 2 blanks (one inside containment and one outside), 1 sealed (unopened) blank
• B. 3 inside containment, 7 outside, 2 blanks, 1 sealed
• C. 6 inside containment, 4 outside, 2 blanks
• D. 5 inside containment, 5 outside, 1 blank, 2 sealed blanks

Answer: (A)

In this TEM clearance z-test, the setup tests for contamination by comparing measurements taken inside containment with those from outside, while also accounting for background and potential contamination through blanks. Having five samples inside provides a solid estimate of the indoor level and its variability, and having five samples outside gives a reliable baseline for the surrounding environment. The two blanks—one inside containment and one outside—serve to reveal any contamination introduced during the sampling or analysis process specific to each location. The sealed blank, kept unopened, ensures there’s no pre-existing contamination from packaging or transport affecting the blank result. This combination gives enough replication for a meaningful z-test and robust checks against contamination sources, which is why it is the best fit. Other arrangements either reduce replication, omit a critical control (the sealed blank), or don’t properly separate inside/outside contamination sources, weakening the test’s reliability.