Who is correct regarding calibration gases?

• A. Technician A only.
• B. Technicians A and B.
• C. Technician B only.
• D. Neither technician.

Answer: (B)

Calibration gases are used to verify and adjust an exhaust analyzer so its readings reflect the true concentrations being measured. To do this correctly, you rely on gases that are certified and traceable to standard references, and you follow the instrument maker’s procedures. A zero gas establishes the baseline, ensuring the instrument reads near zero when there is no pollutant, while a span gas with a known concentration checks that the instrument’s response is accurate across its operating range. Using the appropriate gases for the pollutant being tested and documenting the results ensures the test is valid and compliant.

If both technicians followed these steps—one handling the zero calibration to set the baseline and the other handling the span calibration to set the scale—then both are applying the required calibration gas practices. That joint correctness is why the answer indicates both technicians are correct. Proper calibration also involves equipment checks (correct regulators, leak checks) and using gases within their labeled shelf life, which reinforces why using the right gas and following the procedure matters.