ETC Air Quality & Emissions Monitoring 2 — Questions and Answers
Question 1: Under the Clean Air Act, what is a 'criteria pollutant'?
- Any toxic air pollutant listed under Section 112
- One of six common air pollutants for which EPA has set NAAQS to protect public health and welfare (Correct answer)
- A pollutant that requires a Title V operating permit to emit
- A pollutant identified only by state environmental agencies
Correct answer: One of six common air pollutants for which EPA has set NAAQS to protect public health and welfare
The six criteria pollutants are CO, NO2, SO2, O3, PM2.5/PM10, and lead — pollutants widespread enough for EPA to set health-based ambient standards (NAAQS).
Question 2: What does PM10 refer to in air quality monitoring?
- Particulate matter with an aerodynamic diameter of 10 nanometers or less
- Particulate matter with an aerodynamic diameter of 10 micrometers or less (Correct answer)
- Particulate matter measured at 10 meters above ground level
- Particulate matter with a mass concentration of 10 µg/m³ or more
Correct answer: Particulate matter with an aerodynamic diameter of 10 micrometers or less
PM10 refers to inhalable particles with aerodynamic diameters of 10 micrometers (µm) or less, which can penetrate into the upper respiratory tract.
Question 3: What is 'opacity' as used in air emissions monitoring?
- The total mass of particulate matter emitted per hour from a stack
- The percentage of light obscured by emissions leaving a stack or fugitive source (Correct answer)
- The chemical composition of particulate matter in a plume
- The height above ground at which stack emissions become diluted
Correct answer: The percentage of light obscured by emissions leaving a stack or fugitive source
Opacity is the degree to which emissions block or reduce the transmission of light, expressed as a percentage; it is visually assessed using EPA Method 9.
Question 4: What is a fugitive emission?
- An emission that escapes detection by a CEMS
- An emission released from a source that is not captured by an exhaust hood or stack and vented to the atmosphere directly (Correct answer)
- An accidental release during a plant emergency or malfunction only
- An emission from a mobile source such as a vehicle
Correct answer: An emission released from a source that is not captured by an exhaust hood or stack and vented to the atmosphere directly
Fugitive emissions escape from equipment, seals, or open areas without passing through a control device or stack, such as dust from unpaved roads or leaks from valves.
Question 5: What is the role of a 'zero gas' when calibrating a continuous air quality analyzer?
- A gas containing a certified known concentration of the target pollutant for span calibration
- A gas with no detectable concentration of the target pollutant used to set the instrument's zero response (Correct answer)
- A gas used to purge moisture from the sample line before calibration
- A gas that resets the analyzer's internal clock to a reference time
Correct answer: A gas with no detectable concentration of the target pollutant used to set the instrument's zero response
Zero gas (scrubbed air free of the target pollutant) is introduced to verify and adjust the instrument's zero point so it reads 0 when no pollutant is present.
Question 6: Which Clean Air Act permit program requires large sources emitting above major source thresholds to obtain an operating permit that consolidates all air quality requirements?
- New Source Review (NSR) permit
- Title V operating permit (Correct answer)
- Prevention of Significant Deterioration (PSD) permit
- State Implementation Plan (SIP) permit
Correct answer: Title V operating permit
Title V of the Clean Air Act requires major stationary sources to obtain an operating permit that incorporates all applicable air quality requirements into a single enforceable document.
Question 7: What does the Ringelmann scale measure?
- The concentration of SO2 in flue gas
- The visible density or darkness of smoke emissions from a stack (Correct answer)
- The particle size distribution of stack particulate matter
- The efficiency of an electrostatic precipitator
Correct answer: The visible density or darkness of smoke emissions from a stack
The Ringelmann scale is a visual reference tool using shaded gray cards numbered 0–5 to estimate smoke density/opacity from combustion sources.
ETC Air Quality & Emissions Monitoring 2
Under the Clean Air Act, what is a 'criteria pollutant'?