---

Air issues such as smog and acid rain result from the presence of, and interactions between, a group of pollutants known as criteria air contaminants (CACs) and related pollutants. There are seven CACs listed in Part 4 (see Table 18).

8.1    Reporting Criteria for Part 4 Substances

In contrast to the majority of NPRI substances, the thresholds for CAC emissions are based on the quantity released to air, rather than the quantity manufactured, processed and otherwise used. In general, any person who owns or operates a facility must submit a report to the NPRI for a Part 4 substance if the following criteria are met:

• employees work a total of ≥ 20 000 hours, or
• activities to which the employee threshold does not apply (see Table 3) take place at the facility, or
• employees work a total of < 20 000 hours, and stationary combustion equipment is operated at the facility, or
• the facility is a pipeline installation where stationary combustion equipment is operated (see section 3.5 for the definition of a pipeline installation)

and the total amount of the Part 4 substance released to air is greater than or equal to the release threshold specified in Table 18.

Table 18. Release Thresholds for Criteria Air Contaminants

Criteria Air Contaminant	Release Threshold (tonnes)
Nitrogen oxides (expressed as nitrogen dioxide)	20
Sulphur dioxide
Carbon monoxide
Total particulate matter
Volatile organic compounds	10
Particulate matter with a diameter less than or equal to 10 micrometres (PM10)	0.5
Particulate matter with a diameter less than or equal to 2.5 micrometres (PM2.5)	0.3

Figure 7 illustrates the steps for determining if a report for Part 4 substances is required, and, if so, what information must be reported. For further information on CACs and their reporting criteria, refer to the Criteria Air Contaminants (CACs) Technical Source Guide for Reporting to the National Pollutant Release Inventory (www.ec.gc.ca/inrp-npri/default.asp?lang=En&n=3B695DF5-1) and the Supplementary Guide for Reporting Criteria Air Contaminants (CACs) to the National Pollutant Release Inventory (www.ec.gc.ca/Publications/default.asp?lang=En&xml=4A2D4BB8-BFA0-4129-A5A3-DBA372BD3B32).

Figure 7. Reporting for Part 4 Substances

8.1.1     Part 4 Substance Qualifiers

The following sections provide information on what should be included and excluded when reporting releases of CACs.

Nitrogen oxides

Nitrogen oxides (NO_x) include nitric oxide (NO) and nitrogen dioxide (NO₂). Since NO_x is a mixture, both NO and NO₂ must be expressed on an NO₂-equivalent basis before the individual quantities are combined for the total NO_x release. Do not include nitrous oxide (N₂O) when calculating NO_x releases.

Sulphur dioxide

Sulphur dioxide (SO₂) is part of the sulphur oxide (SO_x) family of gases. However, reporting to the NPRI is only required for SO₂, not SO_x. Therefore, the quantity of the other gases in the SO_x family, (i.e., sulphite, sulphur trioxide [SO₃] and sulphate [SO₄]) released should not be considered when calculating SO₂ releases.

Particulate matter

Three size fractions of particulate matter (PM) are required to be reported to the NPRI:

• total PM with a diameter less than 100 micrometres (TPM)
• PM with a diameter less than or equal to 10 micrometres (PM₁₀)
• PM with a diameter less than or equal to 2.5 micrometres (PM_2.5)

As shown in Figure 8, the TPM fraction includes PM₁₀and PM_2.5, while PM₁₀ includes PM_2.5. It is therefore impossible for PM_2.5or PM₁₀ releases to exceed TPM releases. It is also impossible for PM_2.5 releases to exceed PM₁₀releases.

TPM, PM₁₀ and PM_2.5 emissions must be reported on a dry basis. Only filterable PM is reportable to the NPRI; condensable PM should not be included in release calculations.

Figure 8. Particulate Matter Size Fractions

Volatile organic compounds

Volatile organic compounds (VOCs) are an aggregate grouping of more than 1000 organic substances that readily volatilize and undergo photochemical reactions in the atmosphere.

VOCs should be reported as the total quantity of VOCs that participate in atmospheric photochemical reactions. Do not include any of the substances that are specified as exclusions in section 65 of Schedule 1 of the Toxic Substances List established under CEPA 1999 (for the list of excluded substances, see www.ec.gc.ca/lcpe-cepa/default.asp?lang=En&n=0DA2924D-1&wsdoc=4ABEFFC8-5BEC-B57A-F4BF-11069545E434).

In addition, it is important to note the following:

• Approximately 100 VOCs are listed individually in Part 1A. Individual reports must be submitted for each of these VOCs that meet the Part 1A criteria (based on quantities manufactured, processed or otherwise used). Regardless of whether the Part 1A criteria are met, any releases to air of these substances must also be included in threshold calculations for Part 4 VOCs, along with all other VOCs emitted.
• Base the VOC emissions on the total mass of all VOC substances emitted annually.
• In addition to total VOCs, facilities may be required to report additional information on speciated VOCs listed in Part 5 (see section 9 for more information).
• Total organic compounds (TOCs) and VOCs do not have the same definition. All VOCs can be considered TOCs; however, not all TOCs are considered VOCs.

8.2    Calculating Releases of Part 4 Substances

Table 19 lists some of the most common sources of CAC emissions, with a brief description of each. For more information on these sources of CACs, consult theCAC guidance documents in the NPRI Toolbox (www.ec.gc.ca/inrp-npri/default.asp?lang=En&n=65A75CDF-1).

There are two possible scenarios that must be considered to determine which sources of CAC emissions must be included in threshold calculations. In Case 1, all CAC emission sources at the facility must be included in calculations. In Case 2, only the releases from the stationary combustion equipment at the facility should be included. Each case is described below.

Case 1: Facilities that must consider CAC emissions from all sources

All sources of CAC emissions must be considered when calculating releases (excluding the sources listed in Table 4), if:

• the facility is a contiguous facility, portable facility or offshore installation at which employees work ≥ 20 000 hours; or
• any of the activities to which the employee threshold does not apply (see Table 3) take place at the facility, regardless of the hours worked by employees.

Case 2: Facilities that must consider CAC emissions from stationary combustion equipment only

When calculating releases of Part 4 substances, facilities must consider only emissions from stationary combustion equipment if:

• employees work &lt; 20 000 hours; or
• the only activities that take place at the facility are those listed in Table 5; or
• the facility is a pipeline installation.

A facility that is exempt from reporting Parts 1-3 substances (see section 3.7.3) may still be required to report releases of CACs from stationary combustion equipment.

Table 19. Common Sources of Criteria Air Contaminant Emissions

Source	Description
Abrasive blasting	Abrasive blasting is the process of cleaning or texturing materials with an abrasive material, such as sand, coal and smelter slag, as well as mineral, metallic or synthetic abrasives. The blasting process itself is a source of PM emissions, especially PM10 and PM2.5.
Equipment leaks	Equipment connections, joints and interfaces can be the source of gaseous and liquid releases. If the equipment is handling a gaseous stream containing a CAC, the gaseous leak would result in a fugitive CAC release. Depending on the properties of a liquid (such as vapour pressure, temperature and pressure), a liquid release may also result in a fugitive CAC release.
External combustion equipment	This comprises any equipment with a combustion process that occurs at atmospheric pressure and with excess air, including heaters, furnaces, incinerators, boilers, flares, combustion chambers, external combustion engines such as steam engines and Stirling engines, steam/electric generating plants, and other commercial units.
Fermenting	The process of fermentation involves the use of yeast, bacteria, enzymes, etc., to break down complex organic compounds. Many industries use fermentation, including the production of bread, spirits, pharmaceuticals, fuel, beer and wine, as well as environmental bioremediation processes.
Internal combustion equipment	This comprises any equipment with a combustion process that occurs in a confined space and above atmospheric pressure, including gas turbines, natural‑gas-fired reciprocating engines, gasoline and diesel industrial engines, and large, stationary diesel and dual-fuel engines.
Loading and unloading	Fugitive CAC emissions can result from the loading and unloading of vehicles or containers. If the material being transferred is a liquid, the resulting emissions would likely be in the form of VOCs. If the material is a solid, the resulting emissions would likely be in the form of PM.
Painting	VOCs are released from paint during its application and drying. This category includes, but is not limited to, the painting of vehicles, furniture, storage tanks and any other painted product. PM2.5 may also be emitted if paint is applied by pulverization.
Printing	VOCs are released from fixers, developers and solvents used during printing processes.
Road dust	TPM, PM10 and PM2.5 releases from road dust caused by vehicular traffic on unpaved roads within facility boundaries are required to be included in release calculations, when travel on these roads is ≥ 10 000 vehicle kilometres travelled per year.
Solvent use	Solvent use includes, but is not limited to, solvent degreasing, waste solvent reclamation, product formulation and commercial solvent use. Many solvents contain VOCs that are released during storage, through evaporation.
Stationary combustion equipment	This comprises any combustion equipment that needs to be stationary to function or operate properly, or is not capable of self-propulsion, including both internal and external combustion equipment.
Storage piles	Handling storage piles generates PM emissions. Pile moisture content, wind speed and proportion of aggregate fines all influence total emissions from a storage pile.
Storage tanks	These comprise any storage tanks containing fuels, solvents, hydrocarbons, paints and other solutions that contain VOCs. This includes fixed roof, external floating roof, domed external floating roof, internal floating roof, variable vapour space and pressure storage tanks.

Possible exclusion for Case 2 facilities

A facility that meets the Case 2 criteria is not required to submit reports for CACs, if all the following criteria are met:

• CACs are released to air only from stationary external combustion equipment; and
• the cumulative nameplate capacity of all stationary external combustion equipment is less than 10 million BTUs/hour (10.55 million kJ/hour); and
• the only type of fuel combusted in that equipment is commercial‑grade natural gas, liquefied petroleum gas, Number 1 or 2 fuel oil, or any combination thereof.

This exclusion does not apply if any other fuels are burned in the stationary external combustion equipment.

8.3    Reporting Releases of Part 4 Substances

If the reporting criteria are met for a Part 4 substance, the releases to air of that substance must be reported in tonnes. Case 1 facilities must report all releases from all sources. Case 2 facilities should only report releases from stationary combustion equipment.

Stack-specific releases to air may also need to be reported for each stack ≥ 50 metres (m) above grade, if the stack-specific release threshold specified in Table 20 is met. The following information about each stack must also be reported: height above grade, equivalent diameter, average exit velocity and average exit temperature.

Table 20. Stack-Specific Release Thresholds for Criteria Air Contaminants

Criteria Air Contaminant	Stack Release Threshold (Tonnes)
Nitrogen oxides (expressed as nitrogen dioxide)	5
Sulphur dioxide
Carbon monoxide
Volatile organic compounds
Total particulate matter
Particulate matter with a diameter less than or equal to 10 micrometres (PM10)	0.25
Particulate matter with a diameter less than or equal to 2.5 micrometres (PM2.5)	0.15

Example of stack-specific CAC reporting

A facility releases 25 tonnes of NO_x to air from the whole facility. The facility has a stack that is 55 m above grade and that emitted 7 tonnes of NO_x. The following must be reported:

• 25 tonnes of NO_x must be first reported for total NO_x releases (NO_x has a total release threshold of 20 tonnes); and
• 7 tonnes of NO_x must be reported under the stacks requirement (NO_x has a stack release threshold of 5 tonnes).

---

Part 5 lists 75 VOCs in three groups (individual substances, isomer groups, and other groups and mixtures), which are subject to additional reporting requirements. These VOCs are collectively referred to as “speciated VOCs.” For a list of the speciated VOCs listed in Part 5, consult the NPRI website.

9.1    Reporting Criteria for Part 5 Substances

Like Part 4 substances, speciated VOCs must be reported based on quantities released to air. In general, any person who owns or operates a facility must submit a report to the NPRI for a Part 5 substance if both of the following criteria are met:

• Part 4 total VOCs released to air are ≥ 10 tonnes, and
• the total amount of the Part 5 substance released to air is ≥ 1 tonne.

Figure 9 illustrates the steps for determining if a report for Part 5 substances is required, and, if so, what information must be reported.

Figure 9. Reporting for Part 5 Substances

9.1.1     Part 5 Substance Qualifiers

Some Part 5 substances and groups of substances are qualified in terms of what needs to be included when calculating releases. The qualifiers, described in Table 21, determine whether a report will be required for a given substance.

Table 21. Part 5 Substance Qualifiers

Substance Qualifier	Substance(s) to Which the Qualifier Applies	Description
and its salts	aniline (CAS RN 62-53-3)	Aniline and all salts of aniline must be reported as an equivalent weight of the acid or base.
all isomers	anthraquinone, butane, butene (25167-67-3), cycloheptane, cyclohexene, cyclooctane, decane, dihydronaphthalene, dodecane, heptane, hexene (25264-93-1), methylindan (27133-93-3), nonane, octane, pentane, pentene, terpenes (68956-56-9) and xylene (1330-20-7)	Total of all isomers reported as an aggregate of the individual isomers
	hexane	Total of all isomers reported as an aggregate of the individual isomers, excluding n-hexane (110-54-3)
	trimethylbenzene (25551-13-7)	Total of 1,2,3-trimethylbenzene (526-73-8) and 1,3,5-trimethylbenzene (108-67-8) Excludes 1,2,4-trimethylbenzene (95-63-6)

9.2    Calculating Releases of Part 5 Substances

There are two scenarios that must be considered to determine what sources of VOC emissions must be included in threshold calculations for Part 5 substances.

Case 1: Facilities that must consider all sources of VOC emissions

All sources of VOC emissions must be considered when calculating releases (excluding the sources listed in Table 4), if:

• the facility is a contiguous facility, portable facility or offshore installation at which employees work ≥ 20 000 hours; or
• any of the activities to which the employee threshold does not apply (see Table 3) take place at the facility, regardless of the hours worked by employees.

Case 2: Facilities that must consider VOC emissions from stationary combustion equipment only

Only VOC emissions from stationary combustion equipment must be considered when calculating releases if:

• employees work ≥ 20 000 hours; or
• the only activities that take place at the facility are those listed in Table 5; or
• the facility is a pipeline installation.

9.3    Reporting Releases of Part 5 Substances

If the reporting criteria are met for a Part 5 substance, the releases to air of that substance must be reported. Part 5 substances must be reported in tonnes. Stack-specific releases to air may also need to be reported for each stack ≥ 50 m above grade if both of the following criteria are met:

• stack-specific reporting is required for total VOCs under Part 4; and
• 5 tonnes or more of total VOCs under Part 4 are released to air from the stack.

Example of stack-specific speciated VOC reporting

A facility emits 28 tonnes of VOCs to air, 7 tonnes of which are emitted from a stack 65 m above grade. The remaining 21 tonnes are from storage/handling, fugitive releases, spills and other non-point sources. Three tonnes of styrene are released to air, 0.4 tonnes of which are from the 65 m stack. The following must be reported:

Part 4 (total VOCs)

• 28 tonnes of total VOCs must be reported under Part 4 (total VOCs have a release threshold of 20 tonnes)
• 7 tonnes of total VOCs must be reported for the facility’s stack under Part 4 (total VOCs have a stack-specific release threshold of 5 tonnes)

Part 5 (speciated VOCs)

• 3 tonnes of styrene must be reported under Part 5 (speciated VOCs have a release threshold of 1 tonne)
• 0.4 tonnes of styrene must be reported for the facility’s stack (speciated VOCs must be attributed to stack if the speciated VOC meets the facility-wide 1 tonne threshold, and the Part 4 VOC stack release threshold of 5 tonnes is met)
• the remaining 2.6 tonnes of styrene must be reported as being released from “other sources”