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Halogenated Solvent Cleaning NESHAP: What Subpart T Requires of Your Degreaser
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Halogenated Solvent Cleaning NESHAP: What Subpart T Requires of Your Degreaser

Subpart T has not changed since 2007 while TSCA deadlines on the same three solvents kept moving. What the solvent cleaning NESHAP requires of a degreaser.

by iSi Environmental

Between December 2024 and October 2026, EPA moved, stayed or reopened the compliance dates on the three halogenated solvents most likely to be running through a degreaser today. The air rule on the same machine, the halogenated solvent cleaning NESHAP at 40 CFR 63.460 through 63.471, has not changed substantively since 2007.

The trichloroethylene section 6(g) exemption conditions were postponed in May 2026 until judicial review concludes, with no end date (EPA TCE risk management page, FR document 2026-08750). The perchloroethylene Workplace Chemical Protection Program deadlines were extended in July 2026 to three dates in 2027 (EPA PCE risk management page). Methylene chloride laboratory compliance dates were pushed out 18 months in late 2025.

Subpart T was promulgated December 2, 1994 at 59 FR 61805, and its last substantive amendment was 72 FR 25138 on May 3, 2007. EPA’s own information collection renewal states that the regulations “have not changed over the past three years and are not anticipated to change over the next three years” (EPA ICR 1652.11, OMB control number 2060-0273). Nineteen years without a substantive change, and the agency on record expecting three more.

The obligation that keeps running, every February 1 and every month in between, is the one nobody sent an alert about. On a site visit that is reliably where the findings are.

⚡ Start here: Applicability turns on solvent chemistry, not on machine size or facility size. If the six halogenated hazardous air pollutants listed at 40 CFR 63.460(a) total more than 5 percent by weight of what is in the machine, Subpart T applies, whether the plant is a major source or an area source and whatever the degreaser holds. Machine type and size then pick which standard applies, with monitoring at 40 CFR 63.466, recordkeeping at 63.467 and reporting at 63.468.

What is 40 CFR 63 Subpart T, and which degreasers does it cover?

Subpart T is the halogenated solvent cleaning NESHAP at 40 CFR 63.460 through 63.471, promulgated December 2, 1994 (59 FR 61805). It covers batch vapor, in-line vapor, in-line cold and batch cold solvent cleaning machines whose solvent carries any of six halogenated hazardous air pollutants above 5 percent by weight. Wipe cleaning is excluded.

Every compliance date is long past: start-up or December 2, 1994 for machines built after November 29, 1993, December 2, 1997 for those built earlier, and December 2, 1999 for continuous web machines (40 CFR 63.460(c), (d), (g)).

Which solvents trigger Subpart T?

Six, listed at 40 CFR 63.460(a): methylene chloride (CAS 75-09-2), perchloroethylene (127-18-4), trichloroethylene (79-01-6), 1,1,1-trichloroethane (71-55-6), carbon tetrachloride (56-23-5) and chloroform (67-66-3). The trigger is a total concentration greater than 5 percent by weight, provable by EPA test method 18, safety data sheets, or engineering calculations.

Read the safety data sheet. The test runs on what is in the sump today and sums the six listed compounds, so a blend at 3 percent methylene chloride and 4 percent perchloroethylene is over the line. A reformulation can move a machine in or out of scope with nobody filing anything.

Does Subpart T apply to area sources, or only major sources?

Both. Section 63.460(h) addresses area sources directly, exempting them from the part 70 and 71 permit obligation under stated conditions while requiring compliance with the area source provisions, and 63.460(i) extends the 63.471 facility-wide limits to area sources as well. Subpart T has no major-source gate.

Most part 63 standards start with a major-source determination, and a facility under 10 tons per year of any single HAP and 25 combined walks away. Here it happens at the drum, so a single open-top degreaser at a shop with no other part 63 obligation can be the whole scope of the rule. Our post on EPA’s once-in-always-in policy works through how the classification is set.

Is there a size exemption for a small degreaser?

No. Section 63.460 contains no small-machine exemption. The only size-based carve-out is definitional: under 40 CFR 63.461, buckets, pails and beakers of 7.6 liters (2 gallons) or less are not solvent cleaning machines. Machine size decides which standard applies, at a 1.21 square meter (13 square foot) split.

The 2-gallon limit sounds like a threshold but behaves like a definition. A 5-gallon parts washer holding a halogenated solvent is a batch cold cleaning machine under 63.462. Aerospace, narrow tubing and continuous web machines are carved out of the 63.471 facility-wide definition only (40 CFR 63.460(i)).

What control options does a batch vapor degreaser have under Subpart T?

Section 63.463(b) gives size-based menus. At or below 1.21 square meters (13 square feet) of solvent/air interface area, ten control combinations in Table 1. Above 1.21 square meters, seven combinations in Table 2, each requiring three controls rather than two. Existing in-line machines get four options and new in-line machines get three (63.463(c)).

What a combination looks like, from the Table 1 list: a working-mode cover with a freeboard ratio of 1.0 and superheated vapor; a freeboard refrigeration device with superheated vapor; a freeboard refrigeration device with a carbon adsorber. The Table 2 rows for larger machines stack three controls in every case.

For in-line machines, new versus existing status sets the menu instead of size. Existing machines choose from four combinations in Table 3. New machines get three in Table 4, and the new-source list drops the weaker pairings, leaving superheated vapor with a freeboard refrigeration device, a freeboard refrigeration device with a carbon adsorber, or superheated vapor with a carbon adsorber (63.463(c)(1) and (2)).

Three baseline requirements apply whichever combination is chosen: an idling and downtime cover free of cracks and holes, with reduced room draft as an alternative; a freeboard ratio of 0.75 or greater; and automated parts handling at 3.4 m/min (11 ft/min) or less (40 CFR 63.463(a)). Each control carries a parameter to hold: chilled-air blanket temperature in degrees Fahrenheit no greater than 30 percent of the solvent boiling point, reduced room draft at or below 15.2 m/min (50 ft/min), superheated vapor at least 10 degrees Fahrenheit above the boiling point, and carbon adsorber exhaust under 100 ppm (63.463(e)(2)). Those parameters are monitored at the frequencies set by 40 CFR 63.466.

What is the idling-mode emission limit, and when would I use it instead?

0.22 kg/hr/m² (0.045 lb/hr/ft²) of solvent/air interface area for batch vapor machines in either size class, and 0.10 kg/hr/m² (0.021 lb/hr/ft²) for in-line machines, whether existing or new (40 CFR 63.463(b) and (c)). It is the alternative to picking a control combination off Tables 1 through 4.

Compliance here is demonstrated by testing under 63.465(a) and appendix A rather than by equipment inventory. The route suits a machine that already performs well because of how it was built, particularly an airless or airtight design, where the test costs less than a retrofit it does not need.

Can I comply by limiting solvent consumption instead of adding controls?

Yes, under the 40 CFR 63.464 alternative standard. Machines with a solvent/air interface get a 3-month rolling monthly average limit of 150 kg/m² per month for batch vapor, 153 for existing in-line and 99 for new in-line (Table 5). Batch vapor machines without an interface use Table 6 or EL = 330 × (Vol)^0.6 kg per month.

Table 6 runs by cleaning capacity, in kilograms per month: 0.05 m³ allows 55, 0.10 m³ allows 83, 0.25 m³ allows 144, 0.50 m³ allows 218, 1.00 m³ allows 330, 1.50 m³ allows 421, 2.00 m³ allows 500, 2.50 m³ allows 572 and 2.95 m³ allows 632, with Equation 1 taking over above 2.95 m³. Where a machine’s capacity falls between two table sizes, the lower limit applies.

What the route costs is bookkeeping. Section 63.464(a)(1)(i) requires a solvent addition and deletion log, monthly compliance is determined under 63.465(b) and (c), and the rolling calculation sheets are 5-year records under 63.467(c).

What work practices does Subpart T require on a vapor degreaser?

Twelve, at 40 CFR 63.463(d). Parts or baskets may not occupy more than 50 percent of the solvent/air interface area unless they are introduced at 0.9 m/min (3 ft/min) or less. Spraying happens only within the vapor zone or in a baffled section not directly exposed to ambient air. Nothing comes out of the machine until dripping stops.

The list is where deviations get written:

  • The cover stays in place during idling and downtime unless the solvent has been removed or maintenance requires otherwise.
  • In an open-top batch machine, baskets or parts may not occupy more than 50 percent of the solvent/air interface area unless they are introduced at 0.9 m/min (3 ft/min) or less.
  • Spraying happens only within the vapor zone, or in a baffled or enclosed section not directly exposed to ambient air.
  • Parts are oriented so solvent drains freely, and cavities and blind holes are tipped or rotated before removal.
  • Nothing is removed until dripping has stopped.
  • Vapor machines follow the prescribed startup and shutdown sequence.
  • Solvent transfer uses threaded or leakproof couplings with the pipe end beneath the liquid surface.
  • Maintenance follows the manufacturer’s recommendations.
  • Operators pass the appendix A test if asked to.
  • Waste solvent, still bottoms and sump bottoms go into closed containers.
  • Sponges, fabric, wood and paper products may not be cleaned in the machine.

Most of these cost nothing and fail anyway, because nobody wrote them into a work instruction. The 50 percent basket rule and the drip rule are the two an inspector can stand there and watch.

What does Subpart T require for a cold-cleaning dip tank?

Section 63.462. An immersion batch cold machine needs a tightly fitting cover plus either a water layer at least 2.5 cm (1.0 inch) thick or a freeboard ratio of 0.75 or greater. Remote-reservoir machines need a sump cover closed except during cleaning. Parts drain 15 seconds or until dripping stops, whichever is longer.

Nine work and operational practices sit at 63.462(c): waste solvent in closed containers, flushing only within the freeboard, parts drained for the full interval, solvent kept below the fill line, spills wiped up immediately, agitation without splashing, drafts with the cover open held at or below 40 m/min (132 ft/min), and no cleaning of sponges, fabric, wood or paper products, with a narrow PCB transformer exception at (c)(9). Alternative measures achieving equivalent or better control can be requested under (e). EPA counts 163 batch cold cleaning facilities in the regulated universe, and these are the machines most often missed in an inventory, because they read as a parts washer rather than as air pollution control equipment.

What reports does a Subpart T facility file, and when?

An annual report by 1 February for 63.463 machines, carrying an operator-training statement and a solvent consumption estimate (40 CFR 63.468(f)). An annual solvent emission report for 63.464 machines under (g). Exceedance reports semiannually, moving to quarterly after an exceedance, due by the 30th day after each period ends under (h).

The exceedance clock is self-ratcheting. One exceedance moves the facility to quarterly reporting until EPA approves a reduced frequency under 63.468(i). On the current calendar, the 2026 annual report is due February 1, 2027 and the July through December exceedance report January 30, 2027.

A facility that acquires or starts a covered machine files an initial notification within 120 days of becoming subject (63.468(a), (b)), with the initial statement of compliance following under (d) and (e).

How long must Subpart T records be kept?

Two tiers, at 40 CFR 63.467. For the life of the machine: manuals or maintenance and operating procedures, the installation date or certification letter, dwell test records, idling test records, the halogenated HAP content of each solvent, and squeegee or air-knife records. For 5 years: monitoring results, corrective actions, annual consumption estimates and carbon adsorber exhaust results.

The 5-year tier is ordinary. The life-of-machine tier produces the findings, because it reaches back before most of the staff.

What a Missing 1993 Certification Letter Actually Costs

Section 63.467(a) requires, for the life of the machine, either the installation date or a certification letter stating that the machine was installed before or after November 29, 1993. That letter establishes new versus existing status, and that status decides which table of control options applies. For in-line machines the new-source table drops the weaker combinations, so the answer changes what equipment is sufficient.

Thirty-two years on, a degreaser bought used, relocated, or picked up in an acquisition frequently has none of it. No manual, no installation date, no certification letter, no record of the HAP content of the solvent now in the sump. The machine may be physically compliant with a Table 2 combination and still be undocumentable.

EPA’s own count of the regulated universe is roughly 931 facilities, 768 batch vapor and in-line plus 163 batch cold, at 31,300 annual labor hours (EPA ICR 1652.11). A population that size is not a mass inspection program. It is a rule a facility gets found out of compliance with during a title V review, a permit renewal, or an inspection that began over something else.

What are the Subpart T facility-wide solvent consumption limits?

Section 63.471 sets 12-month rolling totals by solvent in its Table 1: 4,800 kilograms of perchloroethylene, 14,100 kilograms of trichloroethylene and 60,000 kilograms of methylene chloride for the general population, rising to 8,000, 23,500 and 100,000 kilograms for military depot maintenance. Compliance is demonstrated on the first operating day of each month.

A facility using more than one solvent weights its total against a methylene-chloride-equivalent figure using coefficients A = 12.5 and B = 4.25, and the combined limit is the same 60,000 and 100,000 kilograms. Applicability covers all machines at a major source except aerospace, narrow tubing and continuous web, and at an area source all machines except batch cold (63.471(a)). A facility that has never summed consumption across every machine has a gap it does not know about.

Is the Subpart T NESHAP still the rule that binds my degreaser, or has TSCA taken over?

Both apply, and neither displaces the other. EPA’s compliance guide for the 2024 TCE rule lists 40 CFR part 63 subpart T, “Halogenated Solvent Cleaning,” among the potentially applicable national emission standards for hazardous air pollutants, alongside the TSCA section 6(a) rule. Nothing in the primary sources says TSCA supersedes the NESHAP.

Three of the six Subpart T solvents carry TSCA section 6(a) rules, and those obligations stack on top of the air rule.

For trichloroethylene (89 FR 102568, December 17, 2024), the interim existing chemical exposure limit is 0.2 ppm as an 8-hour time-weighted average with an action level of 0.1 ppm, and section 6(g) exemptions run to December 18, 2031 for essential aerospace parts, narrow medical device tubing and Federal rocket engine cleaning. The December 18, 2026 date for processing as a reactant or intermediate and for industrial and commercial processing-aid use is live as of today, five weeks out. EPA proposed on October 14, 2026 to move it to December 31, 2027 (docket EPA-HQ-OPPT-2026-7327), and that is not final. Our post on the TCE section 6(g) postponement covers what the conditions require.

Perchloroethylene (89 FR 103560, December 18, 2024, 40 CFR part 751) is different: vapor degreasing continues under the Workplace Chemical Protection Program and is not prohibited. The July 2026 extension gives non-federal owners and operators initial monitoring by June 21, 2027, the ECEL, regulated area, training, respiratory protection and PPE program by September 20, 2027, and the exposure control plan by December 20, 2027.

For methylene chloride the ECEL is 2 ppm (8 mg/m³) as an 8-hour time-weighted average (89 FR 39254, May 8, 2024). Whether its industrial uses remain allowed is covered in our post on methylene chloride’s consumer ban and continuing industrial use.

Has EPA updated Subpart T recently?

No. The last substantive amendment was 72 FR 25138, May 3, 2007. EPA’s information collection renewal (OMB control number 2060-0273) states the regulations “have not changed over the past three years and are not anticipated to change over the next three years” (EPA ICR 1652.11). No residual risk and technology review for Subpart T, proposed or final, was located.

The EPA page for the subpart carries a rule history ending with an October 20, 2008 notice of reconsideration and a December 3, 2008 comment period extension, and the agency’s risk and technology review status page shows a halogenated solvent cleaning row with dates in 2006 and 2007 and nothing in the 2020s. For a facility planning capital work on a degreaser, the control requirements will not shift underneath the decision. The compliance file is where the attention is overdue.

Where Your Reports Go, and What Your State Adds

Missouri holds delegation through the Department of Natural Resources Air Pollution Control Program, Subpart T listed by name at reference dates 7/1/24 and 9/30/25 (EPA delegation of authority to Missouri). Submittals go to MDNR in Jefferson City with duplicates to EPA Region 7 in Lenexa. Missouri is temporarily not accepting delegation for area source NESHAP in Subparts WWWWW through EEEEEEE, and Subpart T sits outside that range.

Oklahoma holds delegation through DEQ’s Air Quality Division under 63.99(a)(37)(i), effective November 21, 2018, Subpart T listed (83 FR 53183). Submittals go directly to ODEQ in Oklahoma City, and in the notice’s words, “Sources do not need to send a copy to the EPA.” Delegation is a specific list rather than a standing grant: “Any amendments made to these rules after September 1, 2016 are not delegated,” the grant excludes Indian country, and non-delegated authorities still go to EPA Region 6.

Absent delegation, reports go to the appropriate EPA Regional Office (40 CFR 63.9(a)(4) and 63.10(a)(4)). Kansas and Nebraska sit in Region VII at 11201 Renner Boulevard, Lenexa, Kansas 66219, and Texas in Region 6. Confirm delegation status before the first filing, because a report sent to the wrong agency is unfiled.

The federal NESHAP is also only a floor. Several states and air districts regulate solvent degreasers under VOC rules independent of part 63, which can add control, logging or permitting duties on the same machine. Our post on paint booth air permit requirements walks the state trigger methodology for a sibling piece of equipment.

Work the Determination in This Order

Pull the safety data sheet for every solvent in every cleaning machine and total the six listed halogenated HAP by weight. Over 5 percent and the machine is in scope, whatever the facility’s HAP tonnage. Classify each covered machine as batch cold, batch vapor, in-line cold or in-line vapor, and for batch vapor measure the solvent/air interface area against 1.21 square meters (13 square feet). Establish new versus existing status from the November 29, 1993 date, and write the certification letter now if the installation date cannot be documented. Pick the compliance route and write down why. Confirm the two initial filings are on file, calendar the February 1 report and the exceedance clock, then sum consumption against the 63.471 limits.

A facility with no Subpart T file is not automatically in violation. It has never written down the answer, a smaller problem to fix before someone else asks the question.

iSi’s air permitting team runs NESHAP applicability determinations for solvent cleaning operations, builds the life-of-machine documentation behind them, weighs the control combination against the idling-mode and consumption alternatives, and sets the reporting calendar. To have a degreaser determination checked before a permit review asks for it, talk to an iSi environmental specialist. We respond the same day.

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Frequently Asked Questions

Does the solvent cleaning NESHAP apply to small shops?

Yes, if the chemistry matches. Applicability turns on what is in the machine, not on machine or facility size, and Subpart T reaches area sources as well as major sources.

Which solvents trigger Subpart T?

The listed halogenated hazardous air pollutants, including trichloroethylene, perchloroethylene, and methylene chloride, when they total more than 5 percent by weight of the solvent in the machine, per 40 CFR 63.460(a).

Has Subpart T changed recently?

No. It was promulgated December 2, 1994 and last substantively amended May 3, 2007 at 72 FR 25138. The deadlines that have been moving since 2024 are TSCA risk management actions on the same solvents, a separate program from the air rule.

What ongoing obligations does Subpart T carry?

Monitoring under 40 CFR 63.466, recordkeeping under 63.467, and reporting under 63.468, which run continuously whether or not the TSCA deadlines on the same solvents move.

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