Air Quality Testers: Who Measures, Models and Assesses Air Quality?

What do air quality testers actually do?

The phrase air quality testers sounds as though the job is simply to take an instrument outside, collect a sample and see what it says.

Sometimes that is exactly what is needed. Industrial air-quality work can also involve emissions calculations, CEMS, ambient monitoring, meteorological observations, dispersion modelling, regulatory reporting, audits and detailed technical investigations.

The common thread is a simple question: What is in the air, where did it come from, what happens to it and what should we do about it?

Stuff in the Air began in 2003 as a site for explaining meteorology and environmental science. Over time, the air-quality side has grown from general educational material into a practical resource covering industrial emissions, monitoring, modelling and regulatory work.

This page is the doorway. From here you can explore the science of air quality, learn what an air-quality professional actually does or move into detailed resources on modelling, monitoring and emissions.

Air Quality Testers: Three Ways We Learn About Air Quality

A useful way to understand the field is to divide the work into three broad approaches.

1. Measure it - Instruments can measure pollutant concentrations directly.

Examples include:

• ambient air monitoring stations
• portable and mobile monitors
• CEMS
• stack testing
• meteorological sensors
• passive samplers
• laboratory analysis

Alberta's monitoring system includes continuous ambient stations, industrial monitoring and continuous emissions monitoring. Data are subject to quality-control and quality-assurance processes under the Alberta Air Monitoring Directive and the CEMS Code.

2. Calculate it - Sometimes the quantity of pollution cannot simply be measured continuously.

Emission rates may instead be determined from engineering information, production data, equipment characteristics, published emission factors, stack testing or other accepted methods.

Calvin Consulting prepares Alberta Annual Emissions Inventory Report Quantification Methodologies and submission forms for many clients. We have also developed procedures for determining emissions and other source parameters for equipment such as tanks, engines, external-combustion equipment, fugitive sources and flares.

3. Model it - Sometimes the important question is not simply how much was emitted, but: Where will it go? That's where dispersion modelling comes in.

Models such as AERMOD and CALPUFF use emissions, meteorology, terrain, receptors and other information to estimate ground-level concentrations. Alberta currently identifies AERSCREEN for screening and AERMOD-PRIME and CALPUFF for refined assessments.

Good air quality testers therefore need to understand when a measurement, calculation or model is the appropriate tool.

What Is Air Quality?

Air quality describes the condition of the air around us. It depends on what substances are present, their concentrations and how those concentrations change through time and space.

Improvements in Alberta's air quality

Some substances occur naturally. Others come from transportation, industry, agriculture, fires, dust, combustion and many other sources.

Meteorology has a major influence because wind, temperature, atmospheric stability, precipitation and mixing determine how substances move and disperse. That is why air quality and meteorology are so closely connected.

Want the basics first? What Is Air Quality? explains the subject from the ground up.

What Can Affect Air Quality?

Air pollution can come from many different sources. Industrial sources can include:

• combustion equipment
• process vents
• storage tanks
• flares
• engines
• fugitive emissions
• material handling
• roads and other dust sources

Transportation is another major source of many pollutants. Natural processes matter too, including wildfire smoke, dust and biological emissions.

Indoor air presents a different set of questions involving building ventilation, occupant activities and indoor sources. The important lesson for air quality testers is that the source determines much of what needs to be measured or calculated. A monitoring strategy designed for a refinery stack won't necessarily be the right strategy for indoor air.

Measure, Calculate or Model?

Suppose a client asks: How much pollution are we releasing? That may be primarily an emissions-quantification question.

Suppose the question is: What is the concentration at our fence line? That could involve monitoring, modelling or both.

Suppose the question is: Will the new facility affect nearby locations? Dispersion modelling may be appropriate.

Suppose the question is: Our reported numbers don't agree with the equipment records. Which one is right? Now the job may be an investigation.

This is where professional judgement begins.

The most useful air quality testers are not simply people who know how to operate instruments or software. They understand what each source of evidence can and cannot tell them.

What Does an Air-Quality Professional Actually Do?

A professional air-quality assessment may involve several disciplines.

Meteorology: Weather data provide the atmospheric conditions needed to understand dispersion.

Processing meteorological data commonly includes examining windroses and statistical summaries as well as preparing the files needed by the dispersion model.

At Calvin, windroses and statistical charts may be produced using WRPlot View or summary functions associated with AERflare workflows.

Emissions: The modeller or emissions specialist may determine source rates from engineering information, stack tests, CEMS, operating records, emission factors or other information.

Geography: Terrain, land use, buildings and nearby sources can affect the assessment.

Modelling: AERMOD, CALPUFF, AERflare and ABflare may be used where appropriate.

Regulation: The assessment may need to address legislation, approvals, objectives, guidelines or facility-specific conditions.

Communication: The final report has to explain the result to people who may not be atmospheric scientists.

These skills come together every day in professional air-quality work.

The Air-Quality Consultant's Real Job Starts Before the Model Runs

One of the most important things Calvin Consulting does is question the information before relying on it.

• Client information may be incomplete.
• Two records may disagree.
• An emission rate may not fit the operating condition.
• A facility drawing may differ from the information used in a previous assessment.
• A source may have been overlooked.
• A proposed scenario may not represent how the equipment can actually operate.

Those discrepancies matter. An answer can be calculated to many decimal places and still be based on a poor assumption.

An agreement between two professionals

So one of the less obvious skills of professional air quality testers is knowing when a number deserves another question. At Calvin, we investigate inconsistencies rather than quietly choosing whichever number gives the most convenient result.

From Data to a Picture of the Facility

Before detailed dispersion results are presented, Calvin commonly prepares a topographical isopleth drawing showing terrain, broad land-use information, anthropogenic features and receptor locations.

This gives the reader a picture of the physical setting before the modelling begins. It can reveal questions that aren't obvious in a spreadsheet:

• Where are the nearby residences?
• Where are the industrial facilities?
• How does the terrain change?
• Where are the receptors?
• Are there important sources nearby?
• Does the digital representation resemble the real facility?

For a dispersion assessment, the map is part of the reasoning.

Buildings Matter

Air doesn't simply flow around a facility as though every structure were invisible. Buildings can alter airflow and create downwash and other effects that affect plume behaviour.

Calvin uses BPIP where appropriate to parameterize building and stack geometry for dispersion modelling. Reports can include BPIP input and output so the geometry used in the assessment can be reviewed. The process involves checking details such as:

• building dimensions
• roof heights
• building tiers
• stack locations
• stack heights
• nearby structures
• the relationship between sources and buildings

This is another place where experienced air quality testers and modellers add value: the software can calculate what it has been told, but someone has to decide whether the digital facility actually represents the physical one.

When Monitoring and Modelling Work Together

Monitoring and modelling are often treated as separate activities. They can also strengthen one another. Ambient measurements can provide background information. Meteorological observations help explain dispersion.

Much Better because of air quality testers

CEMS (and other source measurements) can improve emission estimates. Model predictions can help determine where monitoring might be useful. Historical data can reveal whether an assumed operating condition is realistic.

Alberta's current data systems provide access to ambient air and industrial emissions information that can support modelling, research and compliance work.

This is why a strong assessment looks at the whole evidence chain.

What Happens When the Numbers Disagree?

Suppose three sources give you three different answers for an emission rate.

A calculation produces one value. A historical report contains another. A monitoring result suggests a third.

Which number should be used? There is no responsible shortcut. The difference might come from:

• different operating conditions
• different averaging periods
• different measurement methods
• changes in equipment
• calculation assumptions
• data-quality problems
• an error in one of the records

Investigating that difference may be more valuable than immediately running another model. This kind of problem is common enough that professional air quality testers need a healthy amount of skepticism.

Air Quality Modelling

Dispersion modelling is one of the more visible parts of Calvin's work, but it is only one part of the larger air-quality picture. A typical assessment may consider:

emissions → meteorology → terrain → buildings → receptors → dispersion → predicted concentrations → regulatory comparison

The important questions include:

• What should be modelled?
• Which emissions should be included?
• Which operating scenarios matter?
• Which receptors are important?
• Which meteorology is representative?
• Which model is appropriate?
• Does the result make physical sense?

The Air Quality Modelling section of Stuff in the Air goes into the professional service side of this work. Air Quality Dispersion Modelling then goes deeper into the science and methodology.

Why Model Results Need Judgment

A computer model can run successfully while the assessment is still wrong. The problem might be the input data.

Data and procedure evaluation by Calvin Consulting

It might be the source representation. It might be the receptor network. It might be the building-geometry.

It might be the model selection. It might be the interpretation. Or the result might actually be correct even though it looks surprising.

That's why Calvin's modelling reports go through several levels of review. One question that comes up repeatedly is: Does the model adequately represent the physical and regulatory problem? This is the practical meaning of professional judgement.

It is also why the air quality testers who work with industrial data need to be comfortable investigating uncertainty rather than hiding it.

Air Quality Statistics Matter Too

A maximum concentration is only one way to describe an air-quality dataset. Depending on the regulatory question, an assessment may use:

• averaging periods
• percentiles
• nth-highest concentrations
• annual averages
• background concentrations
• frequency distributions
• compliance statistics

A model can produce an impressive-looking maximum that has little regulatory meaning unless the correct averaging period and statistical treatment are applied.

The Air Quality Statistics section provides a more detailed introduction.

What About Cars, Indoor Air and Natural Gas Leaks?

Air quality is a big subject. The Stuff in the Air library includes information about transportation emissions, indoor air pollution and natural gas leak detection because these are important air-quality topics in their own right.

Potential source of gas leaks

They also illustrate why air quality isn't synonymous with industrial stack emissions. The appropriate question depends on the setting.

A car exhaust, an office building, a sour-gas facility and a wildfire plume create very different measurement and assessment problems. That's why the broader Stuff in the Air library includes both general educational material and specialized industrial resources.

What Regulations Have to Do With It

In Alberta, air quality is managed through the Environmental Protection and Enhancement Act, regulations and related requirements.

AAAQOs and AAAQGs are important regulatory tools for ambient air quality. Applicable activities requiring an EPEA approval, operating under a Code of Practice or otherwise subject to modelling requirements may need air-quality modelling to demonstrate impacts relative to these objectives or guidelines.

The Air Monitoring Directive establishes requirements for monitoring and reporting. Alberta's current resources include procedures for calibration, audits, data quality and reporting.

Industrial air-reporting submissions include ambient data, monitoring reports, CEMS-related information and other required documents through Alberta's electronic reporting systems.

The details change over time, which is one reason a professional assessment should always start with the requirements applicable to the particular facility and project.

The Professional Advantage Is Knowing What to Question

Good air-quality work involves uncertainty. There may be missing data. There may be conflicting records. There may be assumptions that need testing.

A model may produce an unexpected maximum. An instrument may produce an unexpected measurement. An engineering design may create an unforeseen environmental problem.

Experience helps a professional decide which questions are worth pursuing. Where I work, at Calvin Consulting, that questioning is part of the work.

We discuss unusual results with one another. We review one another's work. We question supplied information when it doesn't appear complete or consistent. We look for obvious design problems before they become expensive problems.

Sometimes the answer requires more modelling. Sometimes it requires better data. Sometimes the best solution is an engineering change. And sometimes the analysis already available is sufficient.

Why Call an Air-Quality Specialist?

Modern environmental software is increasingly accessible. That's a good thing. A person who understands atmospheric science can learn to operate many of these tools.

The difficult part comes earlier. 

• Which emissions belong in the assessment?
• Which operating conditions matter?
• Is the data complete?
• Is the meteorology representative?
• Where should the receptors go?
• Does the building representation make sense?
• Which regulatory criterion applies?
• Does the result make physical sense?

And perhaps the most important question: Are we spending money solving the actual problem?

A consultant can spend days or weeks producing a technically impressive assessment that answers the wrong question if those decisions are made incorrectly at the beginning.

That is why involving an experienced specialist early can be much cheaper than discovering a modelling problem after an application has been submitted or an engineering design has been finalized. You can learn to run the software. The valuable part is learning what to ask it, what to challenge and what the answer actually means.

Calvin Consulting works with industrial clients, engineers, operators and project teams across Western Canada to turn air-quality questions into defensible decisions. Start with the question. Then decide what needs to be measured, calculated or modelled.

Contact Calvin Consulting Group Ltd. to discuss an air-quality question, a proposed project or an existing assessment. Send Barry Lough, EP of Calvin Consulting a quick message at:

...for quicker, more detailed answers. 

A certified Environmental Professional (EP) will provide you with the best assistance on your project.

Keep Exploring Stuff in the Air

Stuff in the Air began with a simple curiosity:

What's in the air?
All kinds of stuff.
See what we can find.

Today that curiosity leads in several directions.

You can explore weather and meteorology, learn about atmospheric science, investigate air pollution or dig into the professional side of industrial air quality.

Air quality testers are only one part of that larger story. The more you learn, the more interesting the air becomes.

The Stuff in the Air Air-Quality Library (summary)

This page is the starting point. The more specialized questions have their own homes.

Start with the fundamentals

• What Is Air Quality?
• Air Pollution Facts
• Air Quality Statistics

Learn how the atmosphere helps determine the answer

• Computers in Meteorology
• Air Dispersion Model

Understand industrial sources

• Natural Gas Leak Detection
• Benzene Emissions
• Output SO₂

Learn how modelling works

• Air Quality Modelling
• AERMOD
• AERMOD Model
• Expert Judgement

Explore broader environmental applications

• Environmental Impact Assessment
• Air Pollution by Cars
• Indoor Air Pollution

Find regulatory material

• ERCB Applications and the newer Alberta regulatory material should be treated as historical or jurisdiction-specific resources where applicable rather than assumed to represent today's regulator or requirements.
• The goal is to let the reader move from a general question into increasingly specialized material without having to know the professional vocabulary first.

Take a look at the most recent Calgary, Edmonton and other Alberta air quality index values.

There was a time when stuffintheair provided regular articles.  These monthly emails covered airmodels, weather, air quality testers and other topics covered in environmental science and meteorology classes.  Although the e-zine is no longer being produced, you can still take a look at a few previous issues.

What Does a Professional Air-Quality Consultant Do for Industry?

Calvin Consulting's work can include:

• Emissions
• AEIR Quantification Methodologies and submissions
• emissions inventories
• emission calculations
• source characterization
• fugitive emissions
• CEMS-related work
• Monitoring
• ambient monitoring
• monitoring-station review
• data quality
• QA/QC
• reporting
• audits
• CEMS quality assurance
• Modelling
• AERMOD
• CALPUFF
• AERflare
• ABflare
• building downwash
• cumulative assessments
• flare modelling
• specialized pollutant assessments
• Regulatory work
• approval applications
• renewals and amendments
• Code of Practice requirements
• flare applications
• regulatory responses
• technical information requests
• Investigation and review
• reviewing previous modelling
• checking supplied data
• investigating discrepancies
• evaluating whether additional modelling is necessary
• providing technical advice before engineering decisions are finalized

This is a much better description of air quality testers than imagining one person standing beside a smokestack with a handheld instrument.

Do you have concerns about air pollution in your area??

Perhaps modelling air pollution will provide the answers to your question.

That is what I do on a full-time basis.  Find out if it is necessary for your project.

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Thank you to my research and writing assistants, and the author remains responsible for the content.

A Simple Air-Quality Decision Guide

What are we emitting? - Start with emissions quantification.

Are our measurements reliable? - Look at monitoring, calibration and data quality.

What is happening around our facility? - Consider ambient monitoring.

Where will our emissions go? - Consider dispersion modelling.

Will the project meet the applicable requirements? - Bring together emissions, monitoring, modelling and regulatory interpretation.

Our numbers don't agree. - Investigate the data before assuming another model run will solve the problem.

That last one is particularly important.