Potential-to-Emit Guide for Small Businesses

Purpose and Intended Use of This Guidance

This guidance is intended for owners and operators of sources of air pollution in determining if the source is required to apply for and maintain an operating permit per District Board of Health Regulations Governing Air Quality Management CHAPTER 030 – Source Permitting and Operation.

This guidance may be used to determine potential-to-emit (PTE) under other regulatory programs such as Nonattainment New Source Review (NNSR) and Prevention of Significant Deterioration (PSD). However, the source must note any differences in the other programs that may not be described in this guidance.

 

What is Potential-to-Emit?

Potential to emit (PTE) refers to the highest amounts of certain air pollutants that a source could release into the air at maximum operating capacity (even if the source will never actually emit the highest amount).

The PTE will determine if the source is subject to the permitting requirements of District Board of Health Regulations Governing Air Quality Management CHAPTER 030 and will further classify the source as either “minor” or “major” for regulated air pollutants.

The PTE is a calculation of the maximum potential of the source to emit regulated air pollutants, expressed in tons of pollutant per year for each regulated air pollutant. The PTE must be calculated for continuous 24 hours per day, 365 days per year operation (8,760 hours/year), except for emergency engines which must be calculated at 500 hours per year. In some cases, potential to emit may consider physical and operational design constraints, such as bottlenecks, where the equipment cannot operate continuously. If no constraints or bottlenecks exist, the source must calculate the PTE pre-control and under worst-case conditions for each pollutant. This means that for each listed pollutant emitted by the source, the highest polluting product, raw material, fuel, or operation method must be considered.

Potential to emit will need to be calculated for various permit actions that include (but are not limited to):

1. Construction of a new facility to determine if the source is subject to the permitting requirements of District Board of Health Regulations Governing Air Quality Management CHAPTER 030;
2. Upon renewal of an existing operating permit;
3. Upon installation of new equipment.

 

Regulated Air Pollutants

The Clean Air Act (CAA) regulates air pollutants that may have negative effects on human health and/or the environment. Regulated minor source pollutants include all criteria pollutants, hydrogen sulfide (H₂S), and total reduced sulfur (total reduced sulfur includes H₂S). When calculating the PTE, the focus is on the following categories of pollutants:

Criteria Pollutants

• Particulate Matter (PM), including PM₁₀ (PM less than 10 microns in diameter) and PM_2.5 (PM less than 2.5 microns in diameter)
• Sulfur Dioxide (SO₂)
• Nitrogen Dioxide (NO₂)
• Carbon Monoxide (CO)
• Ground-Level Ozone (O₃), including Volatile Organic Compounds (VOCs) and Nitrogen Oxides (NO_X) as ozone precursors*
• Lead (Pb)

*A precursor of a criteria pollutant is a compound that reacts in the air to produce that pollutant.

Hazardous Air Pollutants (HAPs)

Hazardous Air Pollutants (HAPs) include 188 pollutants that are known to cause or are suspected to cause adverse effects to human health and/or the environment. Some HAPs are also volatile organic compounds (VOCs), and HAPs in solid or liquid form are also considered to be particulate matter (PM). 

Click here for a complete list of HAPs.

 

What are Allowable Emissions?

Allowable Emissions are based on the source's PTE, including consideration of the most stringent of the following: (DBOH 030.010.A)

1. Applicable standards as set forth in 40 CFR PARTS 60, 61, or 63;
2. The applicable Nevada State Implementation Plan (SIP) limitation;
3. The emission rate specified in a permit condition, including those with a future compliance date;
4. An enforceable emissions limitation established in the permit pursuant to an applicable requirement; or
5. An enforceable emissions cap assumed by the source to avoid an otherwise applicable requirement.

The source should consider its business practices and practicality of the requested Allowable Emissions. Allowable Emissions must be legally and practically enforceable and the source must be able to demonstrate compliance through monitoring, recordkeeping, and reporting. Legally and practically enforceable conditions may limit the emissions of the source through use of emissions control equipment, controlled material throughput rates, limiting hours of operation, or other emissions control methods. It is the responsibility of the source to identify any proposed monitoring, recordkeeping, and reporting to ensure compliance with any emission, throughput, production, material type and composition, operational, or other limitation.

Allowable Emissions will be used to establish emissions limits in the permit and annual permit maintenance fees. Allowable Emissions should be representative of a source’s normal operating conditions. A source will be invoiced an Annual Maintenance Fee plus an Annual Emission Fee based on the highest single allowable pollutant identified. A source with a combined hazardous air pollutant (HAP) allowable emissions of greater than or equal to one (1) ton per year will also be invoiced the HAP Source Maintenance and Emission Fee. Permit maintenance fees are further discussed below under, "How Are Annual Permit Maintenance Fees Determined?".

 

Source Classification

A source can be classified into the following three categories: Major, Natural or True Minor, or Synthetic Minor. A source can be a minor source for some pollutants and a major source for other pollutants.

Major Source

A major stationary source is a facility that emits, or has the PTE, one or more regulated pollutant or HAP, at levels equal to or greater than specified emission thresholds defined by the EPA. A source may be major for one or more criteria pollutants and/or one or more hazardous air pollutants. In general, these sources include:

1. A source with a potential to emit 100 tons per year, or more, of any regulated air pollutant;
2. A source with a potential to emit 10 tons per year, or more, of any single hazardous air pollutant or 25 tons per year, or more, of any combination of hazardous air pollutants.

There are several programs that apply to specific categories of major sources, such as the Title V Program, National Emissions Standards for Hazardous Air Pollutants (NESHAP) and the Prevention of Significant Deterioration (PSD) Program. These programs have specific requirements that apply to sources that are considered major in that category.

Natural or True Minor Source

A natural or true minor stationary source is a facility that emits, or has the PTE, of one or more regulated pollutant or HAP, at levels less than major source thresholds under its physical and operational design. In other words, the source does not need any enforceable restrictions (such as emissions limits, use of add-on control equipment, and/or restrictions on input, output, throughput, material or fuel composition, or hours of operation) to qualify as a minor source.

Synthetic Minor Source

A synthetic minor stationary source is a facility that otherwise emits, or has the PTE, of one or more regulated pollutant or HAP in amounts that are at or above the threshold for major sources, but is subject to one or more enforceable restrictions (such as emissions limits, use of add-on control equipment, and/or restrictions on input, output, throughput, material or fuel composition, or hours of operation) that reduce its potential to emit to less than those major source thresholds. Such restrictions must be legally and practically enforceable.

 

Applicability Procedures and Emissions Calculations

Applicability Procedures

The following procedures shall be used to determine whether a new source or a modification to an existing source requires a Permit to Construct (PTC) and/or Permit to Operate (PTO).

1. Applicability is first determined on the basis of whether the source is of the type or size exempted from the permit requirements of District Board of Health Regulations Governing Air Quality Management (DBOH) CHAPTER 030 – Source Permitting and Operation.
   1. Exempt and insignificant emissions units and activities are listed in DBOH SECTION 030.020.B. If your source is listed in SECTION 030.020.B, it is exempt and does not require a permit with the following exceptions:
      1. If the source consists of multiple activities or emissions units, certain activities may be exempt, while other activities may require a permit.
      2. If the source PTE, including emissions from insignificant and exempt emissions units and activities, is equal to or greater than the minor source permitting thresholds, a permit will be required.
      3. A source which consists solely of insignificant and/or exempt activities, and which exceeds the minor source permitting thresholds, may be required to obtain a permit as determined by the Control Officer.
      4. If an insignificant or exempt emissions unit or activity is subject to PART 70 regulations as defined in DBOH PART 030.500 or 030.510, a permit will be required.
      5. Although an emissions unit or activity may be exempt or insignificant, certain air pollution control requirements and limitations in DBOH CHAPTERS 020 and 040 may still apply.
   2. If the source’s PTE, including emissions from insignificant and exempt emissions units and activities, is less than the minor source permitting thresholds, a permit is not required.
2. The source’s PTE must be determined on a pollutant-by-pollutant basis to determine if the PTE is equal to or greater than the minor source permitting thresholds defined in DBOH 030.020.A.5.a.(1). Emissions from insignificant and exempt emissions units and activities must be included in the PTE calculations.

Emissions Calculations

The source’s PTE must be calculated for each source of air pollution on a pollutant-by-pollutant basis. The PTE must then be totaled to determine if the entire source has a PTE equal to or greater than the minor source permitting thresholds listed in DBOH 030.020.A.5.a.(1). A source whose PTE is equal to or greater than the minor source permitting thresholds requires a permit.

While actual emissions are the amount of contaminants emitted by a facility under normal operating conditions using actual operational data, PTE refers to the maximum amount of contaminants that a facility could potentially release into the air.

The PTE process has been broken down and summarized into the following steps, and will be discussed in more detail.

Step 1: Conduct a facility-wide inventory to identify all process equipment and emissions units
Step 2: Gather data for all process equipment and emissions units
Step 3: Categorize emission sources
Step 4: Identify the emissions calculation methods that will be used.
Step 5: If necessary, identify legally enforceable limitations.
Step 6: Calculate the PTE for each emissions source on a pollutant-by-pollutant basis.
Step 7: Calculate the PTE and establish Allowable Emissions on a facility-wide basis.

Step 1: Conduct a Facility-Wide Inventory

For this first step, you will conduct a facility-wide inventory of all the process equipment and emissions units at the facility. Emissions unit means any part of a stationary source that emits or would have the potential to emit any regulated pollutant. Some emission sources may be categorized as insignificant/exempt emission sources as defined in DBOH SECTION 030.020.B. However, insignificant/exempt emission sources must also be included in the facility-wide inventory and PTE calculations. You should also develop a site diagram and process flow diagram (as applicable) at this step in the process to identify all process equipment and emissions units as they relate to the facility. A process flow diagram is not required for sources that do not move material/products from one emissions unit to another (e.g., gasoline stations) or for sources with standalone emissions units (e.g., emergency backup generator, boilers, etc.).

Step 2: Gather Data for all Process Equipment and Emissions Units (EU's)

Gather data for all process equipment and emissions units (EU’s). Be sure to also include any equipment or processes not located in the main building. For example, if an emergency backup generator is located outside of the building, it is still a part of the facility. You may also have equipment that you don’t operate but is still present at the facility. If the equipment is still operable it must be included in your PTE calculations. Any insignificant/exempt emissions units or activities, as defined in DBOH SECTION 030.020.B, and any ancillary (or supporting) activities, must also be included in your PTE calculations. An example of a supporting activity is cleaning of paint application equipment which is cleaned with solvents that subsequently evaporate into the atmosphere.

Your emissions unit inventory list should include make, model and serial numbers, and capacities. In some cases, you may not have the make, model, and/or serial number for equipment, but this can be added later on in the application process. At a minimum, you must know the designed and anticipated capacity of the equipment. You should also assign an emissions unit ID (EU ID), which is a fictitious, unique identification number assigned to each emissions unit identified in a facility site diagram, process flow diagram, or emissions unit list. The facility site diagram and the process flow diagram (if applicable) should identify the emissions units with their respective EU ID.

Click here to download worksheets for common emissions unit and control device types which are available on the AQMD website, under Forms and Applications.

Below is a list of some information you should gather if it is applicable to your source type:

• Existing Permit to Operate/Construct number. Look for any existing Permits issued to the facility including the Permit Number, which will begin with AAIRXX-XXXX.
• Safety Data Sheets (SDS). This information will determine what pollutants may be emitted. For example, for a surface coating operation, gather SDS's for the coatings and solvents used.
• Performance test results. Collect data from stack tests that have been conducted or any other type of test conducted on the performance of the equipment, raw materials, or emissions. 
• Capture and control efficiency of air pollution control equipment. If you have an air pollution control device (e.g., baghouse, scrubber, etc.), the manufacturer should be able to provide you with documentation that shows the percentage of a particular pollutant that the device will capture and/or control.
• Vendor information. e.g., maximum application rate of spray guns (gallons/hour), maximum heat input capacity of boilers (Btu/hr), maximum capacity of fans that exhaust pollutants (cubic feet of air/minute), production rates (product/hour or product/minute), fuel usage rate of generators (gallons or cubic feet of fuel/hour), etc.

Step 3: Categorize Emission Sources

Some emission sources may be categorized as insignificant/exempt emission sources as defined in DBOH Regulations 030.020.B; however, the emissions from all sources, including insignificant/exempt sources, must be included in the PTE calculation.

Step 4: Identify the Emissions Calculation Method(s) That Will be Used

While there may be a variety of methods available to calculate the PTE, the commonly used methods include performance test data, mass balance calculations, and/or emissions factors. You may need to use a combination of these methods to calculate the PTE on a facility-wide basis.

• Performance Test Data

Performance test data may include data from a stack test, continuous emission monitoring, or manufacturer testing. This data must be revised to reflect the maximum hourly operating rate of the process if the equipment was not operating at that level during the performance test.

Performance test data may provide an emission rate as well as other data, such as air flow rate, that is useful in calculating the PTE.

• Mass Balance

In the mass balance approach, it is assumed the weight of all raw materials going into a process must equal the weight of the product and waste material leaving the process. Mass balance is typically the most effective way to calculate emissions from operations that involve solvent evaporation such as coating lines, printing lines, and clean-up activities.

• Emission Factors

If you cannot calculate your emissions using either of the above methods, you may consider using an emission factor. Emission factors exist for many types of sources and processes. Emission factors are an average emission value derived from industry data. Emission factors are usually expressed as the weight of air contaminant released per volume or weight of the activity/fuel/material (e.g., 100 lbs NO_x/10⁶ scf natural gas).

You will need to know your equipment capacity or design rating to use an emission factor. Emission factors for air contaminants can be found in EPA's AP-42, Compilation of Air Pollutant Emission Factors. You may also access EPA's Factor Information Retrieval (WebFIRE) database, which allows you to search all of the EPA emission factors.

It is important to ensure that the factor being used is appropriate for your processes or equipment, and that you pay close attention to the units used with an emission factor. For example, there are three sets of emission factors available for natural gas-fired boilers depending on the firing rate.

Emission factors only provide an estimate of your emissions. For this reason, the AQMD may require the facility to conduct performance testing for some processes or equipment types to more accurately quantify the emissions.

Click here to access EPA's AP-42, Compilation of Air Pollutant Emission Factors

Click here to access EPA's Factor Information Retrieval (WebFIRE) Database

Step 5: If necessary, identify legally enforceable limitations

For purposes of calculating the PTE, control devices or measures can qualify as limitations only if they are inherent to the process and if they are operated and maintained continuously for reasons other than air quality protection. Examples of using controls for purposes other than for air quality include quality control, product recovery, or operating efficiency. The following list of questions should be considered in making a decision as to whether a certain device should be treated as a control device or measure or as inherent to the process.

1. Is the primary purpose of the equipment to control air pollution?
2. Where the equipment is recovering product, how do the cost savings from the product recovery compare to the cost of the equipment?
3. Would the equipment be installed if no air quality regulations were in place?

If the answers to these questions suggest that the equipment should be considered as an inherent part of the process, then the effect of the equipment or practices can be taken into consideration when calculating PTE. If you have determined that the effect of a control device or measure is an inherent part of the process, you must include a detailed justification in your application.

The requested Allowable Emissions can take into consideration any legally and practically enforceable limitations through use of emissions control equipment, controlled material throughput rates, limiting hours of operation, or other emissions control methods. The source must identify any proposed monitoring and recordkeeping that will be used to ensure compliance with any emission, throughput, production, material type and composition, operational, or other limitation. For example, if a source is proposing to limit hours of operation on a generator to determine the requested Allowable Emissions, the source may propose that hours will be monitored through an hour meter on the engine.

• State, Local, or Federal Rules

State and/or federal rules may include requirements that can be used to restrict your PTE. Below are examples of a legally enforceable limitation contained in a federal rule. It is important to note that performance testing may be required to demonstrate compliance with any limits found in a state, local or federal rule.

 

Example 1: 40 CFR PART 63 Subpart HHHHHH – National Emission Standards for Hazardous Air Pollutants: Paint Stripping and Miscellaneous Surface Coating Operations at Area Sources

• 63.11173(e)(2)(i) states “All spray booths, preparation stations, and mobile enclosures must be fitted with a type of filter technology that is demonstrated to achieve at least 98 percent capture of paint overspray...”
• This means that a source that is subject to this federal rule may apply a control efficiency of 98% to their surface coating operation when calculating the PTE for particulate matter (PM) emissions.

 Example 2: 40 CFR PART 60 Subpart I – Standards of Performance for Hot Mix Asphalt Facilities

• 60.92(a)(1) states “No owner or operator subject to the provisions of this subpart shall discharge or cause to be discharged into the atmosphere from any affected facility any gases which contain particulate matter in excess of 0.04 gr/dscf.”
• This means that a source subject to this federal rule may apply this emissions limit when calculating the PTE for particulate matter (PM) emissions.

Step 6: Calculate the PTE for each emissions source on a pollutant-by-pollutant basis.

When calculating the PTE, it is important to show your work. You must identify all sources of data used in the calculations, the calculation methodology, and assumptions made.

You will also need to account for any inherent physical limitations, or bottlenecks, in your process(es) that would limit the potential to emit. When a process is limited by the capacity or rate of one piece of equipment or process, that unit or process is considered a bottleneck. To include the effect of a bottleneck on the PTE, the limitation must be unavoidable, meaning it would be impossible to operate at a higher rate than the bottleneck rate.

Step 7: Calculate the PTE and Allowable Emissions on a facility-wide basis.

Once you have calculated the PTE for each individual process and/or emissions unit, you must total the PTE for the entire facility on a pollutant-by-pollutant basis to classify the source as Major, True Minor, or Synthetic Minor. Then, you will need to calculate the Allowable Emissions for each individual process and/or emissions unit and total the Allowable Emissions for the entire facilty on a pollutant-by-pollutant basis which may be equal to, or less than, the calculated PTE. Allowable Emissions will establish emissions limits in the permit and annual permit maintenance fees.

 

How are Annual Permit Maintenance Fees Determined?

Permit maintenance fees are due annually for the duration of an active Permit to Construct (PTC) and/or Permit to Operate (PTO). In some cases, a source may maintain both a PTO for existing equipment and a PTC for construction of new equipment or modification of existing equipment. The table below describes how annual permit maintenance fees are invoiced.

 

This table describes annual permit maintenance fees for new and modifying Minor and Synthetic Minor sources.

A new Minor / Synthetic Minor source will be invoiced an annual Permit to Construct (PTC) maintenance fee plus an annual emission fee based upon the highest single allowable pollutant. A modifying Minor / Synthetic Minor source will be invoiced an annual Permit to Construct (PTC) maintenance fee and an annual Permit to Operate (PTO) maintenance fee plust an annual emission fee based upon the highest single allowable pollutant.
Fee Description	Fee Amount	When Fee is Due
Annual Maintenance Fee - Minor Source (PTC)	$710	Due annually for the duration of an active Permit to Construct (PTC).
Annual Maintenance Fee - Minor Source (PTO)	$710	Due annually for the duration of an active Permit to Operate (PTO).
Annual Emission Fee - Minor Source (Allowable Emissions < 20 tons/year)	$266	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO).
Annual Emission Fee - Minor Source (Allowable Emissions ≥ 20 and < 40 tons per year)	$665	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO).
Annual Emission Fee - Minor Source (Allowable Emissions ≥ 40 and < 60 tons per year)	$1,658	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO).
Annual Emission Fee - Minor Source (Allowable Emissions ≥ 60 and < 80 tons per year)	$4,142	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO).
Annual Emission Fee - Minor Source (Allowable Emissions ≥ 80 and < 100 tons per year)	$10,354	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO).
Annual Maintenance Fee - HAPs Source (Allowable Emissions ≥ 1 ton per year)	$212	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO), for sources with combined HAP allowable emissions of ≥ 1 ton per year.
Annual Emission Fee - HAPs Source (Allowable Emissions ≥ 1 ton per year)	$2,125	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO), for sources with combined HAP allowable emissions of ≥ 1 ton per year.
Annual Equipment Fee - Gasoline Dispensing Source (Per Nozzle)	$98	Due annually for the duration of an active Permit to Construct (PTC) or Permit to Operate (PTO).

For major source application fees and annual permit maintenance fees, please refer to the AQMD Fee Schedule or contact the AQMD at 775-784-7200 or AQMDPermitting@nnph.org.

Click here for the current AQMD fee schedule.