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Potential to Emit (PTE) Calculator

Calculate maximum theoretical emissions using AP-42 factors and compare against major source thresholds

Free PTE calculator for boilers, engines, turbines, and other combustion sources. Uses EPA AP-42 emission factors to estimate uncontrolled and controlled potential to emit for NOx, CO, SOx, PM10, PM2.5, VOC, and CO2. Compares results against Title V major source thresholds (100 tpy criteria, 10/25 tpy HAPs) to screen applicability.

Pro Tip: PTE assumes 8,760 hours at maximum rated capacity. Most facilities operate well below this. If your PTE exceeds thresholds but actual emissions are lower, you may be able to accept federally enforceable limits (synthetic minor) to avoid Title V. Talk to your permitting agency about operational restrictions before assuming you are a major source.

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Potential to Emit (PTE) Calculator
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How It Works

  1. Select Equipment Type

    Choose from natural gas boiler, oil boiler, diesel engine, natural gas turbine, or natural gas engine. AP-42 emission factors load automatically.

  2. Enter Rated Capacity

    Input maximum rated capacity in MMBtu/hr for boilers and turbines, or HP for engines. Use nameplate data, not typical operating load.

  3. Set Operating Hours

    Default is 8,760 hr/yr (24/7/365) for true PTE. Adjust only if you have federally enforceable hour limits in your permit.

  4. Add Control Devices

    Select any installed pollution control equipment. Default efficiencies are pre-filled but can be edited to match your permitted or tested values.

  5. Review Threshold Comparison

    Check each pollutant against the 100 tpy major source threshold. Yellow means approaching (over 80%), red means exceeds. Consider consulting an air permitting specialist if any pollutant is near or above thresholds.

Built For

  • Plant engineers screening new equipment before purchase to check permit requirements
  • Environmental managers determining Title V applicability for existing facilities
  • Consultants preparing preliminary PTE calculations for air permit applications
  • Operations staff evaluating whether adding a backup generator triggers major source status
  • Corporate environmental teams auditing facility permitting status across multiple sites

Assumptions

  • Emission factors are EPA AP-42 averages for the selected source category.
  • Equipment operates at maximum rated capacity for the full operating period.
  • Control device efficiencies reflect properly maintained equipment at steady state.
  • Standard fuel compositions are assumed (e.g., ultra-low sulfur diesel at 15 ppm S).

Limitations

  • Does not account for startup, shutdown, or malfunction emissions.
  • HAP-specific emission factors are not included; only criteria pollutants and CO2 are calculated.
  • Does not perform facility-wide PTE aggregation across multiple sources.
  • Nonattainment area threshold adjustments must be evaluated separately.

References

  • EPA AP-42: Compilation of Air Pollutant Emission Factors, Volume 1, Chapters 1.3, 1.4, 3.1, 3.3, 3.4
  • Clean Air Act Section 302(j) - Major Emitting Facility Definition
  • 40 CFR Part 70 - State Operating Permit Programs (Title V)
  • 40 CFR 51.166 - Prevention of Significant Deterioration of Air Quality

Frequently Asked Questions

PTE is the maximum amount of a pollutant a source could emit if operated at full capacity for every hour of the year (8,760 hours), considering only federally enforceable emission limitations. It represents a worst-case scenario for regulatory purposes. PTE determines whether a facility is classified as a major or minor source under the Clean Air Act.
In most attainment areas, a major source emits or has the potential to emit 100 tons per year of any single criteria pollutant (NOx, CO, SOx, PM10, PM2.5, VOC). For hazardous air pollutants (HAPs), the thresholds are 10 tpy for any single HAP or 25 tpy of combined HAPs. In nonattainment areas for ozone, thresholds for NOx and VOC drop to 25-100 tpy depending on severity classification.
Exceeding the threshold means the facility is potentially a major source and likely needs a Title V operating permit. This brings additional compliance obligations including annual compliance certifications, enhanced monitoring, and permit fees. However, facilities can accept federally enforceable limitations (hour limits, fuel limits, production caps) to keep PTE below thresholds, becoming a synthetic minor source.
For true PTE calculations, you must use 8,760 hours unless you have a federally enforceable limitation in your permit that restricts operating hours. If your permit limits a generator to 500 hours per year and that limit is enforceable, you can use 500 hours in the PTE calculation. Voluntary or state-only limitations typically do not count.
Disclaimer: This calculator provides preliminary PTE estimates using EPA AP-42 emission factors. Actual PTE determinations require consideration of all emission sources at a facility, federally enforceable limitations, and applicable regulatory definitions. Always consult with your state or local air quality agency for formal applicability determinations. ToolGrit is not responsible for permitting or compliance outcomes.

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