CES Air Quality Monitoring & Standards 3 — Questions and Answers
Question 1: The Air Quality Index (AQI) is calculated using which set of pollutants?
- PM2.5, PM10, O3, CO, SO2, NO2 (Correct answer)
- PM2.5, O3, CO, Pb, VOCs
- NOx, SO2, CO, PM10, benzene
- O3, PM2.5, CO, NH3, SO2
Correct answer: PM2.5, PM10, O3, CO, SO2, NO2
The AQI is computed for six pollutants: PM2.5, PM10, ground-level ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide, with the highest sub-index reported.
Question 2: In dispersion modeling, the Pasquill-Gifford stability classes range from A to F, where class A represents:
- Extremely stable nighttime conditions
- Extremely unstable daytime conditions (Correct answer)
- Neutral atmospheric stability
- Moderately stable evening conditions
Correct answer: Extremely unstable daytime conditions
Pasquill-Gifford class A denotes extremely unstable atmospheric conditions (strong insolation, low wind speed), leading to rapid vertical mixing and dilution of pollutants.
Question 3: Which monitoring siting criterion in 40 CFR Part 58 Appendix E specifies the minimum distance a monitor must be from a roadway to measure neighborhood-scale PM2.5?
- 5 meters
- 10 meters
- 25 meters (Correct answer)
- 50 meters
Correct answer: 25 meters
For neighborhood-scale PM2.5 monitoring, 40 CFR Part 58 Appendix E requires the probe inlet to be at least 25 meters from the nearest road edge to avoid direct traffic emission impacts.
Question 4: What is a 'design value' in the context of NAAQS compliance?
- The target emission rate for a facility's air permit
- The statistically derived ambient concentration used to compare against a NAAQS (Correct answer)
- The maximum modeled concentration from a single emission source
- The average of all monitoring data collected in a calendar year
Correct answer: The statistically derived ambient concentration used to compare against a NAAQS
A design value is the ambient air quality statistic — derived from monitoring data per EPA-specified averaging and calculation procedures — compared against the NAAQS to determine attainment status.
Question 5: Continuous Emission Monitoring Systems (CEMS) for SO2 at large point sources must meet performance specifications under:
- 40 CFR Part 75 (Correct answer)
- 40 CFR Part 58
- 40 CFR Part 51
- 40 CFR Part 70
Correct answer: 40 CFR Part 75
40 CFR Part 75 establishes the continuous emission monitoring requirements and performance specifications for SO2, NOx, and CO2 at electric generating units and other large sources.
Question 6: Which chemical reaction is primarily responsible for the formation of ground-level ozone in urban areas?
- NOx + VOCs + sunlight → O3 (Correct answer)
- SO2 + H2O → H2SO4 → O3
- CO + O2 → CO2 + O3
- NH3 + NOx → O3 + N2
Correct answer: NOx + VOCs + sunlight → O3
Ground-level ozone forms when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight through a series of photochemical reactions.
Question 7: A Summa canister used in Method TO-15 must be certified to what vacuum level before field deployment?
- Atmospheric pressure
- −5 in Hg
- Less than 0.5 mm Hg absolute (Correct answer)
- −15 in Hg
Correct answer: Less than 0.5 mm Hg absolute
TO-15 Summa canisters must be cleaned and evacuated to less than 0.5 mm Hg absolute pressure to ensure no residual contamination before sampling ambient VOCs.
CES Air Quality Monitoring & Standards 3
The Air Quality Index (AQI) is calculated using which set of pollutants?