Alberta AMD Fourth Chapter: Fluoride, Stack Testing and Passive Sampler Accuracy

Your facility has collected vegetation samples, completed a stack survey or received passive air monitoring results. How do you know the measurements are reliable enough for regulatory compliance?  Check the fourth chapter.

A laboratory result alone cannot answer that question. Sampling methods must be appropriate, equipment must operate correctly and the records must demonstrate that the measurements are representative and defensible.

The final sections of the fourth chapter of Alberta's Air Monitoring Directive (AMD) address three activities that help industrial operators understand their environmental impacts:

• Vegetation fluoride monitoring: Determining whether industrial fluoride emissions are accumulating in plants or forage.
• Industrial source monitoring: Measuring pollutants released from stacks and evaluating continuous emissions monitoring systems.
• Passive sampler validation: Establishing whether ambient air measurements are sufficiently precise and accurate.

Each requires different methods. All depend on sound quality assurance and a clear understanding of what the results represent.

This guide explains the requirements, illustrates the essential calculations and identifies the checks worth completing before submitting monitoring results.

Sound environmental decisions require defensible data

Which fourth chapter of the AMD Requirements Apply to Your Facility?

An industrial operator's monitoring obligations generally begin with its Environmental Protection and Enhancement Act (EPEA) approval and any applicable codes or regulatory directions.

The following table identifies the relevant requirements in the fourth chapter.

The distinction is important. A vegetation fluoride programme, stack survey and passive air monitoring network answer different environmental questions. And understanding the purpose of each helps determine the methods, quality controls and reporting requirements needed.

1. Vegetation Fluoride Monitoring: What Must Be Authorized?

Certain industrial operations release fluoride compounds that may accumulate in surrounding vegetation. Fluoride can affect plant health and may present concerns for grazing animals that consume contaminated forage.

Where an industrial approval requires vegetation fluoride monitoring, AMD Chapter 4, Section 6 establishes four important requirements.

Fluoride sampling and analysis requirements

Under clauses ME 6-A through ME 6-D, the person responsible must:

1. Submit the proposed vegetation fluoride analytical method to the Director in writing for authorization before monitoring begins.
2. Use only the analytical method authorized in writing.
3. Collect vegetation after rain and dew have dried.
4. Have vegetation samples analyzed on an unwashed basis.

These requirements are especially important because collection and preparation can affect the measured fluoride concentration.

Monitor this!

Why must vegetation samples remain unwashed?

Fluoride may accumulate within plant material and through deposition onto vegetation surfaces. Washing the sample can remove deposited fluoride and change the measurement. Similarly, collecting wet vegetation may affect the fluoride available for analysis. 

The sampling procedure therefore influences the environmental information obtained.

What else should a sampling plan address?

The fourth chapter establishes the analytical authorization and collection requirements. An effective monitoring programme should also consider the following, as applicable to its approval and objectives:

For example, a facility located near agricultural land may need to evaluate fluoride accumulation in forage vegetation.

Dispersion modelling can help identify areas where airborne fluoride concentrations or deposition may warrant investigation. The final sampling design must also consider vegetation characteristics, exposure history and the facility's monitoring obligations.

The key decision: Does the sampling programme measure the vegetation exposure that the approval intends to assess?

2. Industrial Source Monitoring: Are Stack Test Results Representative?

Vegetation monitoring evaluates possible environmental accumulation. Industrial source monitoring moves closer to the origin of the emissions.

Stack testing measures pollutants being discharged from industrial equipment, helping determine emission concentrations, mass emission rates and compliance with applicable requirements.

The fourth chapter addresses industrial source monitoring in Section 7. Three testing activities are particularly important.

Which testing methods are required?

Under ME 7-A, manual stack surveys must follow the Alberta Stack Sampling Code and applicable prescribed analytical methods.

ME 7-B addresses the methods used for RATAs and CGAs, including requirements under Alberta's CEMS Code.

Written authorization from the Director is required before modifying prescribed test methods, as specified in ME 7-C.

Compliance monitoring for industrial emissions.

The related notification and reporting provisions are found in AMD Chapter 9. Additional requirements may be specified in the facility's approval.

A test plan requiring prior regulatory approval should be identified through those applicable requirements rather than assumed to be mandatory for every stack survey.

Why do facility operating conditions matter?

A stack test must be interpreted in the context of how the source was operating during the measurements.

Consider a natural gas-fired compressor engine: A test at reduced load might produce different exhaust temperatures, flow rates and pollutant concentrations from a test conducted near maximum operating capacity.

Those differences can influence both the measured emissions and the predictions obtained from an air dispersion model.

Before testing, the responsible parties should establish:

• Which pollutants and emission limits apply
• Which equipment and operating conditions must be represented
• What sampling methods and access arrangements are required
• Whether regulatory notification or authorization is necessary
• What operational and testing data must be recorded
• How results will be reviewed and reported

An efficient industrial testing workflow

Review approval and applicable code → Define test conditions → Select prescribed methods → Obtain required authorization and give notice → Conduct testing and QA/QC → Review results → Submit required reports

A clear testing strategy can reduce the risk of collecting technically valid measurements under operating conditions that fail to answer the regulatory question.

Connecting source measurements with dispersion modelling

Stack testing can also provide information used in air quality dispersion assessments. Models such as AERMOD and CALPUFF use emission rates and release characteristics to predict concentrations in the surrounding atmosphere.

Reliable source data can support realistic modelling assumptions. However, measured emissions must be evaluated for the operating scenarios represented in the assessment.

A test conducted under one set of conditions may be insufficient to characterize all relevant operating scenarios. Calvin Consulting's experience in industrial dispersion modelling can help determine which source data and operating conditions are relevant to an air-quality assessment.

3. Passive Air Sampling: How Accurate Are the Measurements?

Stack tests characterize releases at the source. Passive air samplers help investigate concentrations in the surrounding environment.

Passive samplers collect selected gaseous pollutants through diffusion over a defined exposure period, typically without an electrical power supply. They are useful for examining spatial concentration patterns and long-term changes across monitoring locations.

Commonly monitored pollutants include sulphur dioxide (SO₂), nitrogen dioxide (NO₂), hydrogen sulphide (H₂S) and ozone (O₃).

However, passive samplers can be influenced by temperature, wind, humidity, exposure duration and sampling design. The appendix to the fourth chapter provides guidance for determining their precision and accuracy.

What is the difference between precision and accuracy?

Imagine several passive samplers exposed to the same known pollutant concentration. They produce almost identical results, but every result is higher than the known value.

The samplers demonstrate good precision, although their measurements are biased.

A strong correlation does not guarantee accurate concentrations. Two instruments can follow the same concentration pattern while consistently disagreeing about the magnitude.

What does the AMD require?

Clause ME 3-M requires passive samplers to be validated over representative ranges of:

• Ambient pollutant concentrations
• Sampling periods
• Wind speed, temperature and humidity

The AMD also establishes requirements for deployment, sampling records, quality control samples and laboratory analysis.

For routine field sampling, clauses ME 3-Q and ME 3-S require at least one method blank and one replicate sample per sampling period, with each also representing at least 10% of the corresponding passive samples deployed.

The appendix provides additional guidance for validation studies, including comparison with a co-located reference monitor. Its recommended performance criteria include:

Important distinction: The appendix provides recommended validation procedures and criteria. The mandatory monitoring requirements appear in the applicable AMD clauses, including Section 3.1. A complete compliance review must consider both.

4. How to Calculate Passive Sampler Bias and Precision

The statistical calculations become easier to understand when we work through an example.

Step 1: Calculate bias

Bias expresses the difference between the sample mean and a known reference concentration.

• Bias (%) = [(x̄ − x₀) / x₀] × 100

Where:

• x̄ is the mean measured concentration.
• x₀ is the known reference concentration.

Suppose seven samplers are exposed to a known concentration of 10 ppb. Their measured concentrations are:

The calculated bias is:

• Bias = [(12.5 − 10) / 10] × 100 = +25%

The samplers overestimate the known concentration by 25% on average.

Step 2: Calculate precision

Precision can be expressed using the coefficient of variation (CV):

• CV (%) = (s / x̄) × 100

Where:

• s is the sample standard deviation.
• x̄ is the sample mean.

For the seven hypothetical results:

• Mean = 12.5 ppb
• Sample standard deviation ≈ 0.342 ppb
• CV ≈ 2.73%

That indicates closely grouped measurements. However, their average remains substantially higher than the reference value.

Step 3: Evaluate the 95% confidence limits

The appendix recommends assessing the confidence limits around the bias, which accounts for uncertainty in the estimated mean. For seven measurements:

• 95% confidence limits of the mean = x̄ ± 2.447 × (s / √7)

Convert each concentration limit to percentage bias using the known reference concentration. For this example, the approximate confidence interval for bias is:

• +21.8% to +28.2%

Although the CV is below 10%, the upper confidence limit exceeds +25%.

The example therefore satisfies the recommended precision criterion but fails the recommended 95% confidence-limit criterion for bias.

This is a hypothetical teaching example illustrating laboratory validation calculations. A complete validation would also need to address representative exposure conditions and applicable field comparisons.

Step 4: Compare passive samples with a reference monitor

Field validation uses paired measurements collected over equivalent sampling periods. And the relationship between passive sampler values and reference method measurements can be examined using:

• Scatter plots
• Correlation coefficients
• Mean percentage error
• Differences between corresponding measurements

The fourth chapter provides the detailed statistical procedures in its appendix.

When concentrations are very low, absolute differences in ppb may also help explain measurement performance. The practical question is whether the samplers are sufficiently reliable for their intended monitoring purpose.

5. What Can Go Wrong Even When Measurements Look Reasonable?

A monitoring programme can produce plausible numerical results while important quality assurance questions remain unanswered. Consider these examples:

• Vegetation: Samples are analyzed correctly, but the analytical method has not received the required written authorization.
• Stack testing: A survey follows the prescribed method, but the documented operating conditions do not establish whether the test represents the required emissions scenario.
• Passive samplers: Duplicate results agree closely, but comparison with a reference monitor reveals systematic overestimation.

In each case, resolving the problem requires understanding the measurement method and the regulatory purpose.

Help us understand air pollution

A lesson from Calvin Consulting's quality assurance work

During a 2026 AMD quality assurance audit, Calvin Consulting identified discrepancies between instrument specifications documented in a monitoring programme's Quality Assurance Plan and its supporting operating procedures.

The discrepancies required reconciliation to establish consistent technical documentation. They did not, by themselves, demonstrate that the monitoring equipment was defective.

The audit illustrates a broader principle:

• Quality assurance requires agreement between the regulatory requirements, the approved procedures, the monitoring records and the actual analytical methods.

That principle applies to vegetation sampling, industrial source testing and passive monitoring alike.

6. Before You Submit: Monitoring Compliance Checklist

Use this checklist as an initial review of environmental monitoring work.

• Have the facility's EPEA approval conditions been reviewed?
• Is the required pollutant or environmental parameter clearly identified?
• Does the sampling programme represent the intended conditions?
• Have required written authorizations been obtained?
• Were prescribed sampling and analytical methods followed?
• Are laboratory qualifications and analytical quality controls appropriate?
• Have instrument calibrations and field QA/QC checks been documented?
• Are blanks, replicates and reference comparisons adequate?
• Have unusual results or deviations been investigated?
• Do the Quality Assurance Plan and operating procedures agree?
• Are the required notifications and reporting forms current?
• Can the final conclusions be traced to the original measurements and supporting records?

The general workflow

Determine obligations → Plan the monitoring → Verify methods and authorizations → Collect samples or measurements → Apply QA/QC → Validate results → Interpret findings → Report and retain records

The same general approach supports all three activities covered in this guide, even though each has its own technical requirements.

How Calvin Consulting Can Help

Environmental monitoring can involve several specialists: facility engineers, field technicians, laboratories, stack-testing contractors and regulatory professionals. Coordinating their work requires a clear understanding of the monitoring objectives and the evidence needed to demonstrate compliance.

Calvin Consulting Group Ltd. provides expertise in air quality dispersion modelling, regulatory assessments, Quality Assurance Plans and monitoring programme audits.

Our work can help industrial clients:

• Review monitoring obligations and applicable AMD requirements
• Identify gaps in Quality Assurance Plans and operating procedures
• Evaluate monitoring information and supporting documentation
• Assess whether emission data are representative for dispersion modelling
• Review regulatory questions and the evidence available to answer them
• Identify corrective actions and unnecessary duplication of work
• Support technically defensible environmental reporting

A preliminary review can sometimes establish that existing information is sufficient. In other cases, it may identify a problem that should be resolved before a costly testing programme or regulatory submission proceeds.

This is where experienced technical review offers practical value. The right question at the planning stage can prevent expensive problems at the reporting stage.

Recommended Official References

The following Alberta government resources provide the regulatory foundation for the fourth chapter and related monitoring requirements.

Regulatory note: This article summarizes the edition of AMD Chapter 4 in place at the time of writing. Current government documents, written authorizations, applicable codes and facility-specific approval conditions govern. Recommended practices have been distinguished from the directive's mandatory requirements wherever practical.

Explore Related Stuff in the Air Articles

The fourth chapter connects with several other practical air-quality topics available on Stuff in the Air:

These resources help connect regulatory requirements with the scientific principles behind reliable environmental monitoring.

Need Help Demonstrating Air Monitoring Compliance?

Reliable environmental monitoring begins with selecting the correct methods and establishing what the measurements need to demonstrate.

A properly designed programme makes better use of field sampling, laboratory analysis and regulatory reporting resources. An experienced review can also identify gaps before they result in repeated testing or additional regulatory questions.

Calvin Consulting Group Ltd. can help you evaluate your monitoring requirements, quality assurance documentation and air-quality assessment needs.

For assistance with Alberta AMD compliance, monitoring programme reviews, Quality Assurance Plans, audits or air dispersion modelling, contact:

Calvin Consulting Group Ltd.
Calgary, Alberta
403-547-7557

Email:

Before commissioning additional monitoring or modelling, determine what your existing information already establishes and what the regulator actually needs.

Clean air is our passion. Regulatory compliance is our business.

Here are the last few sections of AMD Chapter 4

To ensure ecological compliance in industrial settings, the Alberta Air Monitoring Directive (AMD) details fluoride analysis, industrial emission monitoring, sampling procedures, and passive sampler accuracy.

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