ETC Air Quality & Emissions Monitoring 1 — Questions and Answers
Question 1: What is the primary purpose of a Continuous Emissions Monitoring System (CEMS)?
- To measure pollutant concentrations in ambient outdoor air
- To provide real-time measurement of pollutant emissions from a stationary source (Correct answer)
- To collect grab samples of stack gases for laboratory analysis
- To model the dispersion of pollutants from a facility
Correct answer: To provide real-time measurement of pollutant emissions from a stationary source
CEMS continuously measure and record pollutant concentrations directly at the emission point (e.g., a stack) in real time to demonstrate compliance with permit limits.
Question 2: What does the acronym NAAQS stand for?
- National Ambient Air Quality Standards (Correct answer)
- National Air Analysis and Quality System
- Nationwide Assessment of Air Quality Sources
- National Authority for Atmospheric Quality and Safety
Correct answer: National Ambient Air Quality Standards
NAAQS stands for National Ambient Air Quality Standards, which are EPA standards for outdoor (ambient) air quality for six criteria pollutants.
Question 3: EPA Method 5 is primarily used to measure which type of air pollutant from stationary sources?
- Sulfur dioxide (SO2)
- Nitrogen oxides (NOx)
- Filterable particulate matter (Correct answer)
- Carbon monoxide (CO)
Correct answer: Filterable particulate matter
EPA Method 5 is the reference method for determining filterable particulate matter emissions from stationary sources using a heated probe, filter, and impinger train.
Question 4: What is the purpose of isokinetic sampling during stack emissions testing?
- To ensure the sample gas is cooled to a standard temperature before measurement
- To match the sampling velocity to the stack gas velocity so representative particulate samples are collected (Correct answer)
- To neutralize acidic gases before they contact the sampling filter
- To maintain a constant flow rate through the sample pump regardless of stack pressure
Correct answer: To match the sampling velocity to the stack gas velocity so representative particulate samples are collected
Isokinetic sampling matches the probe inlet velocity to the stack gas velocity, preventing over- or under-sampling of particulates that would bias results.
Question 5: Which analyzer technology is most commonly used to measure ambient nitrogen dioxide (NO2) concentrations in continuous air quality monitors?
- Non-dispersive infrared (NDIR) absorption
- Chemiluminescence (Correct answer)
- Ultraviolet fluorescence
- Electrochemical cell
Correct answer: Chemiluminescence
Chemiluminescence analyzers detect NO2 by measuring the light emitted when nitric oxide (NO) reacts with ozone; NO2 is converted to NO before detection.
Question 6: What unit of measurement is used for the 24-hour NAAQS standard for PM2.5?
- Parts per million (ppm)
- Micrograms per cubic meter (µg/m³) (Correct answer)
- Milligrams per liter (mg/L)
- Nanograms per cubic meter (ng/m³)
Correct answer: Micrograms per cubic meter (µg/m³)
The PM2.5 24-hour NAAQS is expressed in micrograms per cubic meter (µg/m³), currently set at 35 µg/m³.
Question 7: Which EPA-approved method is used to collect volatile organic compound (VOC) air samples for subsequent laboratory analysis?
- EPA Method 8
- SUMMA canister or Tedlar bag with EPA TO-15 (Correct answer)
- EPA Method 5 impinger train
- High-volume Hi-Vol sampler
Correct answer: SUMMA canister or Tedlar bag with EPA TO-15
SUMMA canisters (evacuated stainless steel) and Tedlar bags, analyzed by EPA TO-15, are standard methods for collecting and analyzing VOCs in ambient or indoor air.
ETC Air Quality & Emissions Monitoring 1
What is the primary purpose of a Continuous Emissions Monitoring System (CEMS)?