AQS Monitoring Tools 2 — Questions and Answers
Question 1: What is the primary purpose of a zero calibration check performed on an ambient air quality analyzer?
- To verify the instrument reads correctly when sampling clean air with no target pollutant present (Correct answer)
- To measure the maximum detectable concentration of the target pollutant
- To confirm the sample flow rate matches the design specification
- To test the data logger's communication link to the DAS
Correct answer: To verify the instrument reads correctly when sampling clean air with no target pollutant present
A zero check verifies the instrument output is at baseline (zero) when exposed to certified zero air, confirming no instrument drift or contamination.
Question 2: Under EPA 40 CFR Part 75, a SO2 CEMS must complete a Relative Accuracy Test Audit (RATA) at what minimum frequency?
- Annually (Correct answer)
- Quarterly
- Semi-annually
- Every two years
Correct answer: Annually
EPA Part 75 requires an annual RATA for SO2 CEMS to compare monitor data against a reference method and verify relative accuracy within 10% or 15 ppm.
Question 3: Per EPA regulations, what is the maximum allowable calibration drift for a SO2 CEMS over a 24-hour period?
- 2.5% of the span value (Correct answer)
- 5% of the span value
- 10% of the span value
- 1% of the span value
Correct answer: 2.5% of the span value
EPA 40 CFR Part 75 Appendix B limits the daily calibration drift of SO2 CEMS to ±2.5% of the span value to ensure data quality.
Question 4: Which EPA document (40 CFR Part 58 Appendix A) establishes network design and QA requirements for the SLAMS ambient air monitoring network?
- Quality Assurance Requirements for SLAMS, PAMS, and NCore Monitoring (Correct answer)
- National Ambient Air Quality Standards Reference Methods
- Performance Audit Handbook for Air Quality Monitors
- Tier 1 Monitoring Protocol for Criteria Pollutants
Correct answer: Quality Assurance Requirements for SLAMS, PAMS, and NCore Monitoring
40 CFR Part 58 Appendix A sets QA requirements—including precision, accuracy, and completeness targets—for the SLAMS, PAMS, and NCore networks.
Question 5: A 'span check' in air quality monitoring involves introducing a certified gas at what approximate concentration level?
- 70–90% of the instrument's upper measurement range (Correct answer)
- 10–30% of the instrument's upper measurement range
- Exactly at the NAAQS standard concentration
- At the instrument's lower detection limit
Correct answer: 70–90% of the instrument's upper measurement range
Span checks use a certified calibration gas at 70–90% of the measurement range to verify the instrument's response at high concentrations is accurate.
Question 6: What distinguishes a NIST-traceable primary calibration standard from a secondary (working) standard used in field monitoring?
- Primary standards are certified directly against NIST reference materials; secondary standards are calibrated against the primary (Correct answer)
- Primary standards are portable; secondary standards are lab-only instruments
- Primary standards measure more pollutants simultaneously than secondary standards
- Primary standards are used only during RATAs; secondary standards are used daily
Correct answer: Primary standards are certified directly against NIST reference materials; secondary standards are calibrated against the primary
A NIST-traceable primary standard has an unbroken calibration chain back to national standards; a secondary (working) standard is certified by comparison to the primary for routine field use.
Question 7: What minimum data completeness percentage is required by EPA 40 CFR Part 58 for valid quarterly monitoring data from a criteria pollutant monitor?
- 75% (Correct answer)
- 90%
- 50%
- 85%
Correct answer: 75%
EPA 40 CFR Part 58 requires at least 75% data completeness per quarter for criteria pollutant monitors so that statistical design values are representative.
AQS Monitoring Tools 2
What is the primary purpose of a zero calibration check performed on an ambient air quality analyzer?