CES Air Quality Monitoring & Standards 2 — Questions and Answers
Question 1: Which EPA method is the federal reference method for measuring ambient PM2.5 concentrations?
- Method TO-15
- 40 CFR Part 50 Appendix L (Correct answer)
- Method 5
- 40 CFR Part 60 Appendix A
Correct answer: 40 CFR Part 50 Appendix L
40 CFR Part 50 Appendix L specifies the gravimetric filter-based federal reference method for measuring PM2.5 in ambient air.
Question 2: The 24-hour NAAQS standard for PM2.5 was tightened in 2024 to:
- 35 µg/m³
- 25 µg/m³
- 15 µg/m³ (Correct answer)
- 12 µg/m³
Correct answer: 15 µg/m³
In February 2024, EPA revised the 24-hour PM2.5 NAAQS from 35 µg/m³ to 9 µg/m³ annual and kept or revised the 24-hour standard to 35 µg/m³, but the annual was lowered to 9 µg/m³; the 24-hour standard remains 35 µg/m³ — however the new 2024 rule set the annual at 9 µg/m³.
Question 3: A PAMS (Photochemical Assessment Monitoring Station) is specifically required to measure:
- SO2 and NOx only
- Ozone precursors including VOCs and NOx (Correct answer)
- PM10 and PM2.5 speciation
- Mercury and air toxics
Correct answer: Ozone precursors including VOCs and NOx
PAMS sites are required to monitor ozone precursors — volatile organic compounds (VOCs) and NOx — to support photochemical modeling and ozone control strategies.
Question 4: What does the term 'attainment area' mean under the Clean Air Act?
- An area that has never exceeded any NAAQS
- An area where air quality meets or is better than the relevant NAAQS (Correct answer)
- An area with no major stationary sources
- An area subject to Prevention of Significant Deterioration rules only
Correct answer: An area where air quality meets or is better than the relevant NAAQS
An attainment area is one in which ambient air quality meets the applicable NAAQS for a given pollutant, as determined by EPA based on monitoring data.
Question 5: Which instrument operating principle is used by a TEOM (Tapered Element Oscillating Microbalance)?
- Beta attenuation of particles on a filter tape
- Change in oscillation frequency of a tapered element as mass accumulates (Correct answer)
- Laser light scattering at 90 degrees
- Flame ionization of carbon-containing particles
Correct answer: Change in oscillation frequency of a tapered element as mass accumulates
A TEOM measures PM mass by detecting changes in the resonant frequency of a vibrating tapered element as particles collect on a filter at its tip.
Question 6: Under 40 CFR Part 58, a minimum data completeness requirement of _____ is needed for a valid annual average NAAQS comparison.
- 50%
- 65%
- 75% (Correct answer)
- 90%
Correct answer: 75%
40 CFR Part 58 Appendix A requires at least 75% data completeness on quarterly and annual bases for valid NAAQS comparisons using ambient monitoring data.
Question 7: A community air monitoring program notices elevated benzene levels near an industrial facility. The most appropriate next step is:
- Immediately shut down the facility
- Conduct source apportionment and health risk screening (Correct answer)
- Switch to a different monitoring method
- Remove the monitor and re-site it farther away
Correct answer: Conduct source apportionment and health risk screening
Elevated benzene triggers source apportionment analysis to identify contributors and a health risk screening to assess community exposure, guiding regulatory action.
CES Air Quality Monitoring & Standards 2
Which EPA method is the federal reference method for measuring ambient PM2.5 concentrations?