Which combination correctly lists the required sample counts for a TEM clearance z-test?

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

Answer: (A)

In a TEM clearance z-test, you need a sampling plan that both compares contamination across the containment boundary and checks for background or handling contamination. The standard setup uses five samples collected inside containment and five outside, giving a balanced dataset to assess any difference across the boundary. To monitor background and the integrity of the sampling process, you include blanks: two of them, one processed inside containment and one outside, so you can detect contamination that might occur during handling in either location. A sealed blank is also included and kept unopened to serve as a true control, confirming that blanks haven’t been contaminated during transport or storage.

Other patterns that deviate from this plan—such as altering outside counts, omitting one of the blanks, or not including a sealed blank—would weaken the control over background contamination and the integrity check, making the test less reliable. Therefore, five inside, five outside, two blanks (one inside, one outside), and one sealed blank best matches the required sampling protocol.