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Construction Air Permits: The Potential-to-Emit Thresholds That Decide Whether You Need One
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Construction Air Permits: The Potential-to-Emit Thresholds That Decide Whether You Need One

Construction air permit thresholds run on potential to emit at maximum design capacity. Federal, Title V and Kansas trigger numbers, plus 2026 penalty figures.

by iSi Environmental

⚡ In short: Whether a new or modified unit needs an air construction permit is decided by potential to emit at maximum design capacity and 8,760 hours a year. Three rule sets apply at once, and in Kansas the lowest trigger is 5 pounds per hour of particulate (K.A.R. 28-19-300(b)), far below the federal 100/250 tons-per-year headline. A control device lowers potential to emit only when the restriction is written into a permit.

The 5-pound-per-hour number nobody checks

Here is how the mistake usually happens. A plant is adding a coating line or debottlenecking a process, someone asks whether an air construction permit is needed, the team checks the number everybody knows, confirms the facility is nowhere near 100 tons per year of anything, and the schedule moves forward.

That answer belongs to a different question. In Kansas a construction approval is required at 5 pounds per hour of particulate matter, 2 pounds per hour of PM10, or 50 pounds per 24 hours of volatile organic compounds, carbon monoxide, or nitrogen oxides (K.A.R. 28-19-300(b)). A single mid-sized coating line or process heater clears those figures without strain. Those state triggers sit one to two orders of magnitude below the federal major-source numbers, and they are the layer that catches facilities in iSi’s region. The term that decides every layer is potential to emit.

What is potential to emit (PTE), and why isn’t it the same as actual emissions?

Potential to emit is “the maximum capacity of a stationary source to emit a pollutant under its physical and operational design” (40 CFR 52.21(b)(4)): maximum design capacity at 8,760 hours per year, not last year’s throughput. A unit running one shift is evaluated as though it ran continuously, unless an enforceable permit limit says otherwise.

That convention drives most of the surprises. A booth operated four hours a day, five days a week is 1,040 hours of real use and 8,760 hours of potential to emit. The only thing that shortens the clock or lowers the rate is a limit on hours, throughput, or control-device operation that is written down and enforceable.

What emission level triggers an air construction permit in Kansas?

K.A.R. 28-19-300(a) requires a construction permit at 25 tons per year of particulate matter, 15 tpy PM10, 10 tpy directly emitted PM2.5, 40 tpy SO2/SO3, 40 tpy VOC, 40 tpy NOx, 100 tpy CO, or 0.6 tpy lead. Below those, a construction approval is still required at 5 lb/hr PM or 50 lb per 24 hours of VOC, CO, or NOx.

Both tiers come before the shovel. The approval tier also sets 2 lb/hr for PM10 and SO2/SO3 and 0.1 lb/hr for lead, and a permit is required when a source becomes subject to 40 CFR parts 60, 61, or 63 regardless of emission rate (K.A.R. 28-19-300). Carve-outs are specific rather than general small-business relief: agricultural-related particulate gets a 100 tpy threshold rather than 25 tpy. There is no employee-count or revenue exemption. Where local agency procedure layers onto the state rule, see Kansas City air permitting requirements.

When does a facility become a major source under PSD?

Under 40 CFR 52.21(b)(1)(i), a source in one of 28 listed industrial categories is major at 100 tons per year PTE of a regulated New Source Review pollutant; any other stationary source is major at 250 tons per year. A physical change at a non-major source also counts if the change alone would be a major source.

The 28 categories are specific industrial descriptions rather than a size test: fossil-fuel steam electric plants above 250 MMBtu/hr heat input, kraft pulp mills, portland cement plants, petroleum refineries, and lime plants among them. A facility outside every listed category gets the 250 tpy figure; being inside one drops the same equipment to 100 tpy. EPA may delegate enforcement to a state, which changes who reviews the application and not the number.

What are the HAP thresholds, and why are they lower than the criteria-pollutant numbers?

40 CFR 70.2 sets Clean Air Act §112 major-source status at 10 tons per year of any single listed hazardous air pollutant or 25 tons per year of any combination. These run on a separate track from criteria pollutants, so a facility well under 100 tpy total can still be a major HAP source on one solvent or coating.

The criteria-pollutant arithmetic comes back comfortable, the file closes, and nobody runs the HAP numbers on the one xylene-bearing coating or the chlorinated degreasing solvent. Title V major-source status is also determined across stationary sources on contiguous or adjacent properties under common control within a single two-digit SIC major group (40 CFR 70.2), so a second building on the same campus is usually not a separate source.

What is a synthetic minor limit, and what does accepting one actually cost?

A synthetic minor limit is an enforceable cap on hours, throughput, or emissions that holds potential to emit below a major-source threshold so the facility avoids PSD or Title V. The cost is permanent: the cap only works if it is legally and practicably enforceable, which means ongoing monitoring, recordkeeping, and reporting to prove you stayed under it.

This is the most common real-world outcome of a potential-to-emit calculation. A facility calculates uncontrolled potential to emit, lands above a threshold it does not want to cross, and takes a cap instead: a limit on annual coating usage, operating hours, or throughput. EPA maintains an application form for the route (EPA form SYNMIN).

The obligation is monthly rather than one-time: a cap on gallons per rolling 12 months means somebody tracks gallons every month, because those records are the only proof it held. Kansas adds a wrinkle worth knowing before the schedule is set: a permit is required specifically when a source requests federally enforceable operational restrictions (K.A.R. 28-19-302(b)). The synthetic minor route is itself a permitting action there.

Does a control device lower my potential to emit?

Only if the control, or the operating restriction behind it, is written into a permit as an enforceable condition. EPA’s January 22, 1996 Seitz/Van Heuvelen interim policy reads “federally enforceable” as “federally enforceable or legally and practicably enforceable by a state or local agency” (EPA Interim Policy on Federal Enforceability Requirement for Limitations on Potential to Emit). An uncredited baghouse lowers actual emissions, not potential to emit.

This is the most expensive misunderstanding in the topic. A facility installs a baghouse rated at 99 percent capture, applies that efficiency to the calculation, and concludes it is under the trigger. With no permit condition requiring the baghouse to operate, the credit does not exist, and a permit that should have been obtained years ago was not.

The blanket federal-enforceability requirement in the PSD and NSR potential-to-emit definitions was vacated by the D.C. Circuit, and EPA never completed the replacement rulemaking the 1996 memorandum promised. A thirty-year-old interim policy is the operative authority on the most consequential term in the analysis, and the test it leaves behind is whether the agency can enforce the restriction and whether you can prove compliance.

How much is a “significant” emissions increase for an existing major source?

40 CFR 52.21(b)(23)(i) sets the significance thresholds that turn a change into a major modification: 40 tpy for NOx, SO2, and VOC; 100 tpy CO; 25 tpy PM; 15 tpy PM10; 10 tpy directly emitted PM2.5; 0.6 tpy lead; 7 tpy sulfuric acid mist; 3 tpy fluorides. These are increments above baseline, not total facility emissions.

A facility already major for a pollutant does not get a second 100-ton allowance for its next project. It gets 40 tons of VOC increase before the change becomes a major modification carrying Best Available Control Technology review, source impact analysis, and air quality modeling. An increase measured from the wrong baseline is as wrong as no calculation, and the baseline is what an agency reviews first.

What is the penalty for building before the permit is issued?

Clean Air Act §113(b) civil judicial penalties run to $124,426 per day per violation for penalties assessed on or after January 8, 2025 (40 CFR 19.4 Table 1). Administrative penalties under §113(d)(1) run $59,114 per day to a $472,901 cap. In 2026 EPA Region 5 settled a pre-construction PSD case for $580,000 (Docket CAA-05-2026-0034).

That order rewards a count-by-count read. EPA Region 5’s action against Continental Tire the Americas LLC in Mount Vernon, Illinois alleged construction of a major modification without a PSD permit, without a BACT analysis, source impact analysis, or air quality modeling, and without BACT-level VOC controls.

Two of the four counts concerned nothing that came out of a stack. They went to the accuracy of the permit application: failing to convert VOC data “as propane” to “as ethanol,” and describing mixing equipment as dedicated to a single production line when it could serve several (35 Ill. Admin. Code § 201.152; 40 CFR 70.5(b)). The penalty attached as much to what the application said as to what the facility emitted.

Removing a control-device requirement, a carbon adsorption system on curing trenches, was itself treated as creating a significant net VOC increase and therefore a major modification (40 CFR 52.21(r)(4)). Taking controls out is a permitting action.

Do changes in operating hours or production rate count as a modification?

Not automatically. Under K.A.R. 28-19-300(c), routine maintenance, parts replacement, and changes in operating hours or production rate are not modifications so long as production stays within the originally approved design capacity and resulting potential to emit stays within existing permit limits. Exceed either and it is a modification.

Two conditions, both of which have to hold. A third shift on equipment already permitted at a capacity that covers it is generally fine; the same shift on equipment whose permit limits annual hours or throughput is a modification, even though no hardware changed. The permitting event can be a scheduling decision made with no capital spend attached, so read the operating permit for hour limits and throughput caps during planning.

How do ozone nonattainment designations change the major-source threshold?

Sharply, and downward. Under 40 CFR 70.2 the VOC and NOx major-source threshold drops from 100 tpy in Marginal and Moderate areas to 50 tpy in Serious, 25 tpy in Severe, and 10 tpy in Extreme areas; ozone transport regions trigger at 50 tpy VOC. The same equipment can be minor in one county and major in the next.

A coating operation calculated at 60 tons per year of VOC is minor in a Moderate area and major in a Serious one. Designations also change, so a facility can acquire major-source status without touching its equipment. For how that plays out in a state with substantial nonattainment acreage, see Texas ozone nonattainment air permitting requirements.

If a project makes us a Title V major source, how long do we have to apply?

40 CFR 70.5(a)(1)(i) requires a timely first-time part 70 application within 12 months after the source becomes subject to the permit program, or by an earlier date the permitting authority sets. The clock starts at the change in status, not at the agency’s request for an application.

Nothing arrives in the mail to start it. The source becomes subject when the status change occurs, and the 12 months run from there whether or not anyone at the facility recognized the event. A facility that crosses a threshold in March and discovers it 18 months later is already late, and its own project records document the lateness.

Is EPA loosening the rule that you cannot build before the permit issues?

It has proposed to. On May 13, 2026 EPA proposed narrowing “begin actual construction” so a permit would be required only before constructing pollutant-emitting components, which would allow pads, utility infrastructure, and some multi-use buildings first (91 FR 26958, Docket EPA-HQ-OAR-2025-0618). Comments closed June 29, 2026. No final rule has issued, so the current prohibition still governs.

Site clearing and leveling are already allowed today, and none of the rest of it is law. The prohibition at 40 CFR 52.21(a)(2)(iii) controls, and a major modification may not begin actual construction without a PSD permit in hand.

Where the federal rules are heading, and why that argues for documenting now

Federal pre-construction permitting is being loosened while state triggers stay where they are. Three signals point the same way.

On July 1, 2026 EPA proposed leaving whether, when, and how long to offer public participation for new and modified minor sources entirely to state and local air agencies, on the position that the Clean Air Act does not require public notice or comment for minor sources (EPA news release, July 1, 2026), with a 45-day comment period to follow Federal Register publication. That cuts against the current framing of minor-source air permit public notice requirements. The third signal is historical: PSD’s reach has been narrowed by the courts before, and the potential-to-emit definition is the scar (Seitz/Van Heuvelen memorandum).

Both 2026 items are proposals, and neither changes an obligation today. What survives a rule change in either direction is a documented applicability analysis showing which units were evaluated, at what capacity, against which thresholds, on what date. If the rules loosen, that file is what lets you use the new line; if they do not, it answers the inspector.

Keep one thing in proportion. EPA enforcement priorities for minor-source construction permitting are thinly documented, and most of that enforcement is state-run and never appears in a searchable national docket. The absence of a statistic says where the enforcement happens, not that it is quiet.

Which operations trip these numbers

The categories that recur in iSi’s air permitting work pair modest-looking equipment with real emission factors: surface coating and paint operations, printing, metal fabrication involving abrasive blasting or welding, grain and feed handling, foundries and heat-treat, boilers and process heaters, solvent degreasing, and aggregate and concrete operations. Coating operations tend to clear two triggers at once, VOC on the criteria side and a single HAP on the §112 side; our post on paint booth air permit requirements works through that calculation.

State fee structures and short-form pathways vary, and some exemptions still carry documentation obligations. For Missouri facilities, the current Missouri air construction permit fee schedule covers what the application costs, and the Missouri emergency generator air permit exemption covers one of the more frequently misapplied exemptions. Oklahoma’s minor-facility permit requirements sit at OAC 252:100-7, and EPA proposed approval of updates to Oklahoma’s New Source Review SIP on November 17, 2025 (90 FR 51247) (FR Doc. 2025-19989); confirm its numeric triggers against the state rule before relying on a figure.

What to do before the project schedule locks

  1. Calculate potential to emit for every new or modified emission unit at maximum design capacity and 8,760 hours per year, pollutant by pollutant (40 CFR 52.21(b)(4)).
  2. Credit a control device or operating restriction only if it is, or will be, written into a permit as a legally and practicably enforceable condition. Otherwise calculate uncontrolled (Seitz/Van Heuvelen interim policy, January 22, 1996).
  3. Compare the result against three rule sets: state construction permit and approval thresholds (in Kansas, K.A.R. 28-19-300(a) and (b)), Title V and §112 thresholds (40 CFR 70.2), and federal PSD major-source and significant-modification thresholds (40 CFR 52.21(b)(1) and (b)(23)).
  4. If the result lands above a major-source threshold you do not want to cross, evaluate a synthetic minor limit and price in the monitoring, recordkeeping, and reporting that proves the cap held.
  5. Obtain the permit or approval before construction or modification begins (40 CFR 52.21(a)(2)(iii); K.A.R. 28-19-300).
  6. If the project creates Title V major-source status, submit the application within 12 months of becoming subject, or earlier if the permitting authority sets a date (40 CFR 70.5(a)(1)(i)).
  7. Keep the calculation, the design data behind it, and the emission factors used as the permanent record of the conclusion, including a conclusion that no permit was required.

Expect a completeness review, questions, and a draft permit to review before issuance. Read it closely, because you will be held to what it says.

Where iSi fits

The work here is a specific deliverable: potential-to-emit calculations unit by unit, an applicability review against the state, Title V, and PSD rule sets, synthetic minor evaluation when the numbers land close to a threshold, and application preparation when a permit or approval is required. iSi has run this analysis across 146 air permitting engagements since 2001.

If a capital project is in planning, run the numbers before the equipment is specified, while a cap or a different unit size is still an option. Talk to an iSi air compliance specialist or review our environmental compliance services.

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Frequently Asked Questions

What emission level triggers an air construction permit in Kansas?

A construction permit at 25 tons per year of particulate matter, 40 tpy of VOC or NOx, and the other K.A.R. 28-19-300(a) figures, and a construction approval at far lower rates: 5 pounds per hour of particulate or 50 pounds per 24 hours of VOC, CO or NOx under K.A.R. 28-19-300(b).

What is potential to emit?

The maximum capacity of a source to emit a pollutant under its physical and operational design (40 CFR 52.21(b)(4)): maximum design capacity at 8,760 hours per year, unless an enforceable permit limit says otherwise. Actual operating hours do not reduce it.

What is the penalty for building before the air permit is issued?

Clean Air Act maximums of $124,426 per day per violation judicially and $59,114 per day with a $472,901 cap administratively (40 CFR 19.4, January 2025 levels still in effect). A 2026 EPA Region 5 pre-construction PSD case settled for $580,000.

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