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Subpart GG—National Emission Standards for Aerospace 

Manufacturing and Rework Facilities

§63.741 Applicability and designation of affected sources.

(a) This subpart applies to facilities that are engaged, 

either in part or in whole, in the manufacture or rework of 

commercial, civil, or military aerospace vehicles or components 

and that are major sources as defined in §63.2.

(b) The owner or operator of an affected source shall 

comply with the requirements of this subpart and of subpart A of 

this part, except as specified in §63.743(a) and Table 1 of this 

subpart.

(c) Affected sources. The affected sources to which the 

provisions of this subpart apply are specified in paragraphs 

(c)(1) through (78) of this section. The activities subject to 

this subpart are limited to the manufacture or rework of 

aerospace vehicles or components as defined in this subpart. 

Where a dispute arises relating to the applicability of this 

subpart to a specific activity, the owner or operator shall 

demonstrate whether or not the activity is regulated under this 

subpart.

(1) Each cleaning operation as follows:

(i) All hand-wipe cleaning operations constitute an 

affected source.
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(ii) Each spray gun cleaning operation constitutes an 

affected source.

(iii) All flush cleaning operations constitute an affected 

source.

(2) For organic HAP or VOC emissions, each primer 

application operation, which is the total of all primer 

applications at the facility.

(3) For organic HAP or VOC emissions, each topcoat 

application operation, which is the total of all topcoat 

applications at the facility.

(4) For organic HAP or VOC emissions, each specialty 

coating application operation, which is the total of all 

specialty coating applications at the facility.

(45) For organic HAP or VOC emissions, each depainting 

operation, which is the total of all depainting at the facility.

(56) Each chemical milling maskant application operation, 

which is the total of all chemical milling maskant applications 

at the facility.

(67) Each waste storage and handling operation, which is 

the total of all waste handling and storage at the facility. 

(78) For inorganic HAP emissions, each spray booth or 

hangar that contains a primer or, topcoat, or specialty coating

application operation subject to § 63.745(g)), or a depainting 

operation subject to § 63.746(b)(4).
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(d) An owner or operator of an affected source subject to 

this subpart shall obtain an operating permit from the 

permitting authority in the State in which the source is 

located. The owner or operator shall apply for and obtain such 

permit in accordance with the regulations contained in part 70 

of this chapter and in applicable State regulations. 

(e) All wastes that are determined to be hazardous wastes 

under the Resource Conservation and Recovery Act of 1976 (PL 94-

580) (RCRA) as implemented by 40 CFR parts 260 and 261, and that 

are subject to RCRA requirements as implemented in 40 CFR parts 

262 through 268, are exempt from the requirements of this 

subpart. 

(f) This subpart does not contain control requirements for 

use of specialty coatings, adhesives, adhesive bonding primers, 

or sealants at aerospace facilities. It also does not regulate 

research and development, quality control, and laboratory 

testing activities, chemical milling, metal finishing, 

electrodeposition (except for electrodeposition of paints), 

composites processing (except for cleaning and coating of 

composite parts or components that become part of an aerospace 

vehicle or component as well as composite tooling that comes in 

contact with such composite parts or components prior to cure), 

electronic parts and assemblies (except for cleaning and 

topcoating of completed assemblies), manufacture of aircraft 
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transparencies, and wastewater operations at aerospace 

facilities. These requirements do not apply to the rework of 

aircraft or aircraft components if the holder of the Federal 

Aviation Administration (FAA) design approval, or the holder's 

licensee, is not actively manufacturing the aircraft or aircraft 

components. These requirements also do not apply to parts and 

assemblies not critical to the vehicle's structural integrity or 

flight performance. The requirements of this subpart also do not 

apply to primers, topcoats, specialty coatings, chemical milling 

maskants, strippers, and cleaning solvents containing HAP and 

VOC at concentrations less than 0.1 percent by mass for 

carcinogens or 1.0 percent by mass for noncarcinogens, as 

determined from manufacturer's representations, such as in a 

material safety data sheet or product data sheet, or testing. 

Additional specific exemptions from regulatory coverage are set 

forth in paragraphs (e), (g), (h), (i) and (j) of this section 

and §§ 63.742, 63.744(a)(1), (b), (e), 63.745(a), (f)(3), 

(g)(4), 63.746(a), (b)(5), 63.747(c)(3), and 63.749(d).

(g) The requirements for primers, topcoats, specialty 

coatings, and chemical milling maskants in §§ 63.745 and §63.747 

do not apply to the use of low-volume coatings in these 

categories for which the annual total of each separate 

formulation used at a facility does not exceed 189 l (50 gal), 

and the combined annual total of all such primers, topcoats, 
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specialty coatings, and chemical milling maskants used at a 

facility does not exceed 757 l (200 gal). Primers and, topcoats, 

and specialty coatings exempted under paragraph (f) of this 

section and under § 63.745(f)(3) and (g)(4) are not included in 

the 50 and 200 gal limits. Chemical milling maskants exempted 

under § 63.747(c)(3) are also not included in these limits.

(h) Regulated activities associated with space vehicles 

designed to travel beyond the limit of the earth's atmosphere, 

including but not limited to satellites, space stations, and the 

Space Shuttle System (including orbiter, external tanks, and 

solid rocket boosters), are exempt from the requirements of this 

subpart, except for depainting operations found in §63.746.

(i) Any waterborne coating for which the manufacturer's 

supplied data demonstrate that organic HAP and VOC contents are 

less than or equal to the organic HAP and VOC content limits for 

its coating type, as specified in §§63.745(c) and 63.747(c), is 

exempt from the following requirements of this subpart: 

§§63.745(d) and (e), 63.747(d) and (e), 63.749(d) and (h), 

63.750 (c) through (h) and (k) through (n), 63.752 (c) and (f), 

and 63.753 (c) and (e). A facility shall maintain the 

manufacturer's supplied data and annual purchase records for 

each exempt waterborne coating readily available for inspection 

and review and shall retain these data for 5 years.
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(j) Regulated activities associated with the rework of 

antique aerospace vehicles or components are exempt from the 

requirements of this subpart.

§ 63.742 Definitions.

Terms used in this subpart are defined in the Act, in 

subpart A of this part, or in this section as follows: 

Aerospace facility means any facility that produces, 

reworks, or repairs in any amount any commercial, civil, or 

military aerospace vehicle or component. 

Aerospace vehicle or component means any fabricated part, 

processed part, assembly of parts, or completed unit, with the 

exception of electronic components, of any aircraft including 

but not limited to airplanes, helicopters, missiles, rockets, 

and space vehicles. 

Aircraft fluid systems means those systems that handle 

hydraulic fluids, fuel, cooling fluids, or oils. 

Aircraft transparency means the aircraft windshield, 

canopy, passenger windows, lenses, and other components which 

are constructed of transparent materials.

Antique aerospace vehicle or component means an aircraft or 

component thereof that was built at least 30 years ago. An 

antique aerospace vehicle would not routinely be in commercial 

or military service in the capacity for which it was designed.
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Carbon adsorber means one vessel in a series of vessels in 

a carbon adsorption system that contains carbon and is used to 

remove gaseous pollutants from a gaseous emission source. 

Carbon Adsorber control efficiency means the total 

efficiency of the control system, determined by the product of 

the capture efficiency and the control device efficiency. 

Chemical milling maskant means a coating that is applied 

directly to aluminum components to protect surface areas when 

chemical milling the component with a Type I or Type II etchant. 

Type I chemical milling maskants are used with a Type I etchant 

and Type II chemical milling maskants are used with a Type II 

etchant. This definition does not include bonding maskants, 

critical use and line sealer maskants, and seal coat maskants. 

Additionally, maskants that must be used with a combination of 

Type I or II etchants and any of the above types of maskants 

(i.e., bonding, critical use and line sealer, and seal coat) are 

also exempt fromnot included in this subpartdefinition. (See 

also Type I and Type II etchant definitions.)

Chemical milling maskant application operation means 

application of chemical milling maskant for use with Type I or 

Type II chemical milling etchants.

Cleaning operation means collectively spray gun, hand-wipe, 

and flush cleaning operations. 
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Cleaning solvent means a liquid material used for handwipe, spray gun, or flush cleaning. This definition does not 

include solutions that contain HAP and VOC below the de minimis 

levels specified in §63.741(f).

Closed-cycle depainting system means a dust-free, automated 

process that removes permanent coating in small sections at a 

time and maintains a continuous vacuum around the area(s) being 

depainted to capture emissions.

Coating means a material that is applied to the surface of 

an aerospace vehicle or component to form a decorative, 

protective, or functional solid film, or the solid film itself.

Coating operation means the use of a spray booth, tank, or 

other enclosure or any area, such as a hangar, for the 

application of a single type of coating (e.g., primer); the use 

of the same spray booth for the application of another type of 

coating (e.g., topcoat) constitutes a separate coating operation 

for which compliance determinations are performed separately. 

Coating unit means a series of one or more coating 

applicators and any associated drying area and/or oven wherein a 

coating is applied, dried, and/or cured. A coating unit ends at 

the point where the coating is dried or cured, or prior to any 

subsequent application of a different coating. It is not 

necessary to have an oven or flashoff area in order to be 

included in this definition. 
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Confined space means a space that: (1) Is large enough and 

so configured that an employee can bodily enter and perform 

assigned work; (2) has limited or restricted means for entry or 

exit (for example, fuel tanks, fuel vessels, and other spaces 

that have limited means of entry); and (3) is not suitable for 

continuous employee occupancy. 

Control device means destruction and/or recovery equipment 

used to destroy or recover HAP or VOC emissions generated by a 

regulated operation. 

Control system means a combination of pollutant capture 

system(s) and control device(s) used to reduce discharge to the 

atmosphere of HAP or VOC emissions generated by a regulated 

operation. 

Depainting means the removal of a permanent coating from 

the outer surface of an aerospace vehicle or component, whether 

by chemical or non-chemical means. For non-chemical means, this 

definition excludes hand and mechanical sanding, and any other 

non-chemical removal processes that do not involve blast media 

or other mechanisms that would result in airborne particle 

movement at high velocity. 

Depainting operation means the use of a chemical agent, 

media blasting, or any other technique to remove permanent 

coatings from the outer surface of an aerospace vehicle or 

components. The depainting operation includes washing of the 
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aerospace vehicle or component to remove residual stripper, 

media, or coating residue. 

Electrodeposition of paint means the application of a 

coating using a water-based electrochemical bath process. The 

component being coated is immersed in a bath of the coating. An 

electric potential is applied between the component and an 

oppositely charged electrode hanging in the bath. The electric 

potential causes the ionized coating to be electrically 

attracted, migrated, and deposited on the component being 

coated. 

Electrostatic spray means a method of applying a spray 

coating in which an electrical charge is applied to the coating 

and the substrate is grounded. The coating is attracted to the 

substrate by the electrostatic potential between them. 

Exempt solvent means specified organic compounds that have 

been determined by the EPA to have negligible photochemical 

reactivity and are listed in 40 CFR 51.100. 

Exterior primer means the first layer and any subsequent 

layers of identically formulated coating applied to the exterior 

surface of an aerospace vehicle or component where the component 

is used on the exterior of the aerospace vehicle. Exterior 

primers are typically used for corrosion prevention, protection 

from the environment, functional fluid resistance, and adhesion 
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of subsequent exterior topcoats. Coatings that are defined as 

specialty coatings are not included under this definition.

Flush cleaning means the removal of contaminants such as 

dirt, grease, oil, and coatings from an aerospace vehicle or 

component or coating equipment by passing solvent over, into, or 

through the item being cleaned. The solvent may simply be poured 

into the item being cleaned and then drained, or be assisted by 

air or hydraulic pressure, or by pumping. Hand-wipe cleaning 

operations where wiping, scrubbing, mopping, or other hand 

action are used are not included. 

General aviation (GA) means that segment of civil aviation 

that encompasses all facets of aviation except air carriers, 

commuters, and military. General aviation includes charter and 

corporate-executive transportation, instruction, rental, aerial 

application, aerial observation, business, pleasure, and other 

special uses.

General aviation rework facility means any aerospace 

facility with the majority of its revenues resulting from the 

reconstruction, repair, maintenance, repainting, conversion, or 

alteration of general aviation aerospace vehicles or components.

Hand-wipe cleaning operation means the removal of 

contaminants such as dirt, grease, oil, and coatings from an 

aerospace vehicle or component by physically rubbing it with a 
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material such as a rag, paper, or cotton swab that has been 

moistened with a cleaning solvent. 

Hazardous air pollutant (HAP) means any air pollutant 

listed in or pursuant to section 112(b) of the Act. 

High efficiency particulate air (HEPA) filter means a

filter that has a 99.97 percent reduction efficiency for 0.3 

micron aerosol. 

High volume low pressure (HVLP) spray equipment means spray 

equipment that is used to apply coating by means of a spray gun 

that operates at 10.0 psig of atomizing air pressure or less at 

the air cap.

Inorganic hazardous air pollutant (HAP) means any HAP that 

is not organic. 

Large commercial aircraft means an aircraft of more than 

110,000 pounds, maximum certified take-off weight manufactured 

for non-military use.

Leak means any visible leakage, including misting and 

clouding. 

Limited access space means internal surfaces or passages of 

an aerospace vehicle or component that cannot be reached without 

the aid of an airbrush or a spray gun extension for the 

application of coatings.

Mechanical sanding means aerospace vehicle or component 

surface conditioning which uses directional and random orbital 
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abrasive tools and aluminum oxide or nylon abrasive pads for the 

purpose of corrosion rework, substrate repair, prepaint surface 

preparation, and other maintenance activities. 

Natural draft opening means any opening in a room, 

building, or total enclosure that remains open during operation 

of the facility and that is not connected to a duct in which a 

fan is installed. The rate and direction of the natural draft 

through such an opening is a consequence of the difference in 

pressures on either side of the wall containing the opening. 

Non-chemical based depainting equipment means any 

depainting equipment or technique, including, but not limited 

to, media blasting equipment, that can depaint an aerospace 

vehicle or component in the absence of a chemical stripper. This 

definition does not include mechanical sanding or hand sanding. 

Nonregenerative carbon adsorber means a carbon adsorber 

vessel in which the spent carbon bed does not undergo carbon 

regeneration in the adsorption vessel. 

Operating parameter value means a minimum or maximum value 

established for a control device or process parameter which, if 

achieved by itself or in combination with one or more other 

operating parameter values, determines that an owner or operator 

has complied with an applicable emission limitation. 

Organic hazardous air pollutant (HAP) means any HAP that is 

organic. 
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Primer means the first layer and any subsequent layers of 

identically formulated coating applied to the surface of an 

aerospace vehicle or component. Primers are typically used for 

corrosion prevention, protection from the environment, 

functional fluid resistance, and adhesion of subsequent 

coatings. Coatings that are defined as specialty coatings are 

not included under this definition. 

Radome means the non-metallic protective housing for 

electromagnetic transmitters and receivers (e.g., radar, 

electronic countermeasures, etc.). 

Recovery device means an individual unit of equipment 

capable of and normally used for the purpose of recovering 

chemicals for fuel value, use, or reuse. Examples of equipment 

that may be recovery devices include absorbers, carbon 

adsorbers, condensers, oil-water separators, or organic-water 

separators or organic removal devices such as decanters, 

strippers, or thin-film evaporation units.

Research and Development means an operation whose primary 

purpose is for research and development of new processes and 

products, that is conducted under the close supervision of 

technically trained personnel, and is not involved in the 

manufacture of final or intermediate products for commerical 

purposes, except in a de mimnimis manner. 
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Self-priming topcoat means a topcoat that is applied

directly to an uncoated aerospace vehicle or component for 

purposes of corrosion prevention, environmental protection, and 

functional fluid resistance. More than one layer of identical 

coating formulation may be applied to the vehicle or component. 

Semi-aqueous cleaning solvent means a solution in which 

water is a primary ingredient (′′ 60 percent of the solvent 

solution as applied must be water.) 

Softener means a liquid that is applied to an aerospace 

vehicle or component to degrade coatings such as primers and,

topcoats, and specialty coatings specifically as a preparatory 

step to subsequent depainting by non-chemical based depainting 

equipment. Softeners may contain VOC but shall not contain any 

HAP as determined from MSDS's or manufacturer supplied 

information. 

Solids means the non-volatile portion of the coating which 

after drying makes up the dry film. 

Space vehicle means a man-made device, either manned or 

unmanned, designed for operation beyond earth's atmosphere. This 

definition includes integral equipment such as models, mock-ups, 

prototypes, molds, jigs, tooling, hardware jackets, and test 

coupons. Also included is auxiliary equipment associated with 

test, transport, and storage, which through contamination can 

compromise the space vehicle performance. 
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Specialty coating means a coating that, even though it 

meets the definition of a primer, topcoat, or self-priming 

topcoat, has additional performance criteria beyond those of 

primers, topcoats, and self-priming topcoats for specific 

applications. These performance criteria may include, but are 

not limited to, temperature or fire resistance, substrate 

compatibility, antireflection, temporary protection or marking, 

sealing, adhesively joining substrates, or enhanced corrosion 

protection. Individual specialty coatings are defined in 

appendix A to this subpart and in the CTG for Aerospace 

Manufacturing and Rework Operations (EPA 453/R-97-004).

Spot stripping means the depainting of an area where it is 

not technically feasible to use a non-chemical depainting 

technique. 

Spray gun means a device that atomizes a coating or other 

material and projects the particulates or other material onto a 

substrate. 

Stripper means a liquid that is applied to an aerospace 

vehicle or component to remove permanent coatings such as 

primers and, topcoats, and specialty coatings. 

Surface preparation means the removal of contaminants from 

the surface of an aerospace vehicle or component, or the 

activation or reactivation of the surface in preparation for the 

application of a coating. 
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Temporary total enclosure means a total enclosure that is 

constructed for the sole purpose of measuring the emissions from 

an affected source that are not delivered to an emission control 

device. A temporary total enclosure must be constructed and 

ventilated (through stacks suitable for testing) so that it has 

minimal impact on the performance of the permanent emission 

capture system. A temporary total enclosure will be assumed to 

achieve total capture of fugitive emissions if it conforms to 

the requirements found in §63.750(g)(4) and if all natural draft 

openings are at least four duct or hood equivalent diameters 

away from each exhaust duct or hood. Alternatively, the owner or 

operator may apply to the Administrator for approval of a 

temporary enclosure on a case-by-case basis. 

Topcoat means a coating that is applied over a primer on an 

aerospace vehicle or component for appearance, identification, 

camouflage, or protection. Coatings that are defined as 

specialty coatings are not included under this definition. 

Total enclosure means a permanent structure that is 

constructed around a gaseous emission source so that all gaseous 

pollutants emitted from the source are collected and ducted 

through a control device, such that 100% capture efficiency is 

achieved. There are no fugitive emissions from a total 

enclosure. The only openings in a total enclosure are forced 

makeup air and exhaust ducts and any natural draft openings such 
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as those that allow raw materials to enter and exit the 

enclosure for processing. All access doors or windows are closed 

during routine operation of the enclosed source. Brief, 

occasional openings of such doors or windows to accommodate 

process equipment adjustments are acceptable, but if such 

openings are routine or if an access door remains open during 

the entire operation, the access door must be considered a 

natural draft opening. The average inward face velocity across 

the natural draft openings of the enclosure must be calculated 

including the area of such access doors. The drying oven itself 

may be part of the total enclosure. An enclosure that meets the 

requirements found in §63.750(g)(4) is a permanent total 

enclosure. 

Touch-up and repair operation means that portion of the 

coating operation that is the incidental application of coating 

used to cover minor imperfections in the coating finish or to 

achieve complete coverage. This definition includes out-ofsequence or out-of-cycle coating. 

Two-stage filter system means a dry particulate filter 

system using two layers of filter media to remove particulate. 

The first stage is designed to remove the bulk of the 

particulate and a higher efficiency second stage is designed to 

remove smaller particulate. 
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Type I etchant means a chemical milling etchant that 

contains varying amounts of dissolved sulfur and does not 

contain amines.

Type II etchant means a chemical milling etchant that is a 

strong sodium hydroxide solution containing amines.

Volatile organic compound (VOC) means any compound defined 

as VOC in 40 CFR 51.100. This includes any organic compound 

other than those determined by the EPA to be an exempt solvent. 

For purposes of determining compliance with emission limits, VOC 

will be measured by the approved test methods. Where such a 

method also inadvertently measures compounds that are exempt 

solvent, an owner or operator may exclude these exempt solvents 

when determining compliance with an emission standard.

Waterborne (water-reducible) coating means any coating that 

contains more than 5 percent water by weight as applied in its 

volatile fraction.

Waterwash system means a control system that utilizes

flowing water (i.e., a conventional waterwash system) or a 

pumpless system to remove particulate emissions from the exhaust 

air stream in spray coating application or dry media blast 

depainting operations.

Nomenclature for determining carbon adsorber efficiency—The 

nomenclature defined below is used in §63.750(g): 
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(1) Ak = the area of each natural draft opening (k) in a 

total enclosure, in square meters. 

(2) Caj = the concentration of HAP or VOC in each gas stream 

(j) exiting the emission control device, in parts per million by 

volume. 

(3) Cbi = the concentration of HAP or VOC in each gas stream 

(i) entering the emission control device, in parts per million 

by volume. 

(4) Cdi = the concentration of HAP or VOC in each gas stream 

(i) entering the emission control device from the affected 

source, in parts per million by volume. 

(5) Cfk = the concentration of HAP or VOC in each 

uncontrolled gas stream (k) emitted directly to the atmosphere 

from the affected source, in parts per million by volume. 

(6) Cgv = the concentration of HAP or VOC in each 

uncontrolled gas stream entering each individual carbon adsorber 

vessel (v), in parts per million by volume. For the purposes of 

calculating the efficiency of the individual carbon adsorber 

vessel, Cgv may be measured in the carbon adsorption system's 

common inlet duct prior to the branching of individual inlet 

ducts to the individual carbon adsorber vessels. 

(7) Chv = the concentration of HAP or VOC in the gas stream 

exiting each individual carbon adsorber vessel (v), in parts per 

million by volume. 
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(8) E = the control device efficiency achieved for the 

duration of the emission test (expressed as a fraction). 

(9) F = the HAP or VOC emission capture efficiency of the 

HAP or VOC capture system achieved for the duration of the 

emission test (expressed as a fraction). 

(10) FV = the average inward face velocity across all 

natural draft openings in a total enclosure, in meters per hour. 

(11) Hv = the individual carbon adsorber vessel (v) 

efficiency achieved for the duration of the emission test 

(expressed as a fraction). 

(12) Hsys = the efficiency of the carbon adsorption system 

calculated when each carbon adsorber vessel has an individual 

exhaust stack (expressed as a fraction). 

(13) Mci = the total mass in kilograms of each batch of 

coating (i) applied, or of each coating applied at an affected 

coating operation during a 7 to 30-day period, as appropriate, 

as determined from records at the affected source. This quantity 

shall be determined at a time and location in the process after 

all ingredients (including any dilution solvent) have been added 

to the coating, or if ingredients are added after the mass of 

the coating has been determined, appropriate adjustments shall 

be made to account for them. 

(14) Mr = the total mass in kilograms of HAP or VOC 

recovered for a 7 to 30-day period. 
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(15) Qaj = the volumetric flow rate of each gas stream (j) 

exiting the emission control device in either dry standard cubic 

meters per hour when EPA Method 18 in appendix A of part 60 is 

used to measure HAP or VOC concentration or in standard cubic 

meters per hour (wet basis) when EPA Method 25A is used to 

measure HAP or VOC concentration. 

(16) Qbi = the volumetric flow rate of each gas stream (i) 

entering the emission control device, in dry standard cubic 

meters per hour when EPA Method 18 is used to measure HAP or VOC 

concentration or in standard cubic meters per hour (wet basis) 

when EPA Method 25A is used to measure HAP or VOC concentration. 

(17) Qdi = the volumetric flow rate of each gas stream (i) 

entering the emission control device from the affected source in 

either dry standard cubic meters per hour when EPA Method 18 is 

used to measure HAP or VOC concentration or in standard cubic 

meters per hour (wet basis) when EPA Method 25A is used to 

measure HAP or VOC concentration. 

(18) Qfk = the volumetric flow rate of each uncontrolled gas 

stream (k) emitted directly to the atmosphere from the affected 

source in either dry standard cubic meters per hour when EPA 

Method 18 is used to measure HAP or VOC concentration or in 

standard cubic meters per hour (wet basis) when EPA Method 25A 

is used to measure HAP or VOC concentration. 
Page 23 of 174

(19) Qgv = the volumetric flow rate of each gas stream 

entering each individual carbon adsorber vessel (v) in either 

dry standard cubic meters per hour when EPA Method 18 is used to 

measure HAP or VOC concentration or in standard cubic meters per 

hour (wet basis) when EPA Method 25A is used to measure HAP or 

VOC concentration. For purposes of calculating the efficiency of 

the individual carbon adsorber vessel, the value of Qgv can be 

assumed to equal the value of Qhv measured for that carbon 

adsorber vessel. 

(20) Qhv = the volumetric flow rate of each gas stream 

exiting each individual carbon adsorber vessel (v) in either dry 

standard cubic meters per hour when EPA Method 18 is used to 

measure HAP or VOC concentration or in standard cubic meters per 

hour (wet basis) when EPA Method 25A is used to measure HAP or 

VOC concentration. 

(21) Qini = the volumetric flow rate of each gas stream (i) 

entering the total enclosure through a forced makeup air duct in 

standard cubic meters per hour (wet basis). 

(22) Qoutj = the volumetric flow rate of each gas stream (j) 

exiting the total enclosure through an exhaust duct or hood in 

standard cubic meters per hour (wet basis). 

(23) R = the overall HAP or VOC emission reduction achieved 

for the duration of the emission test (expressed as a 

percentage). 
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(24) RSi = the total mass in kilograms of HAP or VOC 

retained in the coating after drying. 

(25) Woi = the weight fraction of VOC in each batch of 

coating (i) applied, or of each coating applied at an affected 

coating operation during a 7- to 30-day period, as appropriate, 

as determined by EPA Method 24 or formulation data. This value 

shall be determined at a time and location in the process after 

all ingredients (including any dilution solvent) have been added 

to the coating, or if ingredients are added after the weight 

fraction of HAP or VOC in the coating has been determined, 

appropriate adjustments shall be made to account for them. 

§ 63.743 Standards: General.

(a) Except as provided in paragraphs (a)(4) through (a)(10) 

of this section and in Table 1 of this subpart, each owner or 

operator of an affected source subject to this subpart is also 

subject to the following sections of subpart A of this part:

(1) §63.4, Prohibited activities and circumvention; 

(2) § 63.5, ConstructionPreconstruction review and 

reconstructionnotification requirements; and 

(3) §63.6, Compliance with standards and maintenance 

requirements. 

(4) For the purposes of this subpart, all affected sources 

shall submit any request for an extension of compliance not 

later than 120 days before the affected source's compliance 
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date. The extension request should be requested for the shortest 

time necessary to attain compliance, but in no case shall exceed 

1 year. 

(5)(i) For the purposes of this subpart, the Administrator 

(or the State with an approved permit program) will notify the 

owner or operator in writing of his/her intention to deny 

approval of a request for an extension of compliance submitted 

under either §63.6(i)(4) or §63.6(i)(5) within 60 calendar days 

after receipt of sufficient information to evaluate the request. 

(ii) In addition, for purposes of this subpart, if the 

Administrator does not notify the owner or operator in writing 

of his/her intention to deny approval within 60 calendar days 

after receipt of sufficient information to evaluate a request 

for an extension of compliance, then the request shall be 

considered approved. 

(6)(i) For the purposes of this subpart, the Administrator 

(or the State) will notify the owner or operator in writing of 

the status of his/her application submitted under 

§63.6(i)(4)(ii) (that is, whether the application contains 

sufficient information to make a determination) within 30 

calendar days after receipt of the original application and 

within 30 calendar days after receipt of any supplementary 

information that is submitted, rather than 15 calendar days as 

provided for in §63.6(i)(13)(i). 
Page 26 of 174

(ii) In addition, for the purposes of this subpart, if the 

Administrator does not notify the owner or operator in writing 

of the status of his/her application within 30 calendar days 

after receipt of the original application and within 30 calendar 

days after receipt of any supplementary information that is 

submitted, then the information in the application or the 

supplementary information is to be considered sufficient upon 

which to make a determination. 

(7) For the purposes of this subpart, each owner or 

operator who has submitted an extension request application 

under §63.6(i)(5) is to be provided 30 calendar days to present 

additional information or arguments to the Administrator after 

he/she is notified that the application is not complete, rather 

than 15 calendar days as provided for in §63.6(i)(13)(ii). 

(8) For the purposes of this subpart, each owner or 

operator is to be provided 30 calendar days to present 

additional information to the Administrator after he/she is 

notified of the intended denial of a compliance extension 

request submitted under either § 63.6(i)(4) or § 63.6(i)(5), 

rather than 15 calendar days as provided for in §

63.6(1i)(12)(iii)(B) and § 63.6(i)(13)(iii)(B). 

(9) For the purposes of this subpart, a final determination 

to deny any request for an extension submitted under either 

§63.6(i)(4) or §63.6(i)(5) will be made within 60 calendar days 
Page 27 of 174

after presentation of additional information or argument (if the 

application is complete), or within 60 calendar days after the 

final date specified for the presentation if no presentation is 

made, rather than 30 calendar days as provided for in 

§63.6(i)(12)(iv) and §63.6(i)(13)(iv). 

(10) For the purposes of compliance with the requirements 

of § 63.5(b)(4) of the General Provisions and this subpart, 

owners or operators of existing primer or, topcoat, or specialty 

coating application operations and depainting operations who 

construct or reconstruct a spray booth or hangar that does not 

have the potential to emit 10 tons/yr or more of an individual 

inorganic HAP or 25 tons/yr or more of all inorganic HAP 

combined shall only be required to notify the Administrator of 

such construction or reconstruction on an annual basis. 

Notification shall be submitted on or before March 1 of each 

year and shall include the information required in § 63.5(b)(4) 

for each such spray booth or hangar constructed or reconstructed 

during the prior calendar year, except that such information 

shall be limited to inorganic HAP's. No advance notification or 

written approval from the Administrator pursuant to §63.5(b)(3) 

shall be required for the construction or reconstruction of such 

a spray booth or hangar unless the booth or hangar has the 

potential to emit 10 tons/yr or more of an individual inorganic 

HAP or 25 tons/yr or more of all inorganic HAP combined.
Page 28 of 174

(b) Startup, shutdown, and malfunction plan. Each owner or 

operator that uses an air pollution control device or equipment 

to control HAP emissions shall prepare a startup, shutdown, and 

malfunction plan in accordance with §63.6. Dry particulate 

filter systems operated per the manufacturer's instructions are 

exempt from a startup, shutdown, and malfunction plan. A 

startup, shutdown, and malfunction plan shall be prepared for 

facilities using locally prepared operating procedures. In 

addition to the information required in §63.6, this plan shall 

also include the following provisions:

(1) The plan shall specify the operation and maintenance 

criteria for each air pollution control device or equipment and 

shall include a standardized checklist to document the operation 

and maintenance of the equipment; 

(2) The plan shall include a systematic procedure for 

identifying malfunctions and for reporting them immediately to 

supervisory personnel; and 

(3) The plan shall specify procedures to be followed to 

ensure that equipment or process malfunctions due to poor 

maintenance or other preventable conditions do not occur.

[Reserved]

(c) An owner or operator who uses an air pollution control 

device or equipment not listed in this subpart shall submit a 

description of the device or equipment, test data verifying the
Page 29 of 174

performance of the device or equipment in controlling organic 

HAP and/or VOC emissions, as appropriate, and specific operating 

parameters that will be monitored to establish compliance with 

the standards to the Administrator for approval not later than 

120 days prior to the compliance date.

(d) Instead of complying with the individual coating limits 

in §§63.745 and 63.747, a facility may choose to comply with the 

averaging provisions specified in paragraphs (d)(1) through 

(d)(6) of this section.

(1) Each owner or operator of a new or existing source 

shall use any combination of primers, topcoats (including selfpriming topcoats), specialty coatings, Type I chemical milling 

maskants, or Type II chemical milling maskants such that the 

monthly volume-weighted average organic HAP and VOC contents of 

the combination of primers, topcoats, specialty coatings, Type I 

chemical milling maskants, or Type II chemical milling maskants, 

as determined in accordance with the applicable procedures set 

forth in § 63.750, complies with the specified content limits in 

§§ 63.745(c) and 63.747(c), unless the permitting agency 

specifies a shorter averaging period as part of an ambient ozone 

control program.

(2) Averaging is allowed only for uncontrolled primers, 

topcoats (including self-priming topcoats), specialty coatings, 
Page 30 of 174

Type I chemical milling maskants, or Type II chemical milling 

maskants.

(3) Averaging is not allowed between primers and topcoats 

(including self-priming topcoats). Averaging is not allowed 

between specialty coating types defined in Appendix A to this 

subpart, or between the different types of coatings specified in 

paragraphs (d)(3)(i) through (vii) of this section.

(i) Primers and topcoats (including self-priming topcoats).

(ii) Type I and Type II chemical milling maskants.

(iii) Primers and chemical milling maskants.

(iv) Topcoats and chemical milling maskants.

(v) Primers and specialty coatings.

(vi) Topcoats and specialty coatings.

(vii) Chemical milling maskants and specialty coatings.

(4) Averaging is not allowed between Type I and Type II 

chemical milling maskants. [Reserved]

(5) Averaging is not allowed between primers and chemical 

milling maskants, or between topcoats and chemical milling 

maskants. [Reserved]

(6) Each averaging scheme shall be approved in advance by 

the permitting agency and adopted as part of the facility's 

title V permit.

(e) At all times, the owner or operator must operate and 

maintain any affected source, including associated air pollution 
Page 31 of 174

control equipment and monitoring equipment, in a manner 

consistent with safety and good air pollution control practices 

for minimizing emissions. The general duty to minimize emissions 

does not require the owner or operator to make any further 

efforts to reduce emissions if levels required by the applicable 

standard have been achieved. Determination of whether a source 

is operating in compliance with operation and maintenance 

requirements will be based on information available to the 

Administrator which may include, but is not limited to,

monitoring results, review of operation and maintenance 

procedures, review of operation and maintenance records, and 

inspection of the source.

§ 63.744 Standards: Cleaning operations.

(a) Housekeeping measures. Each owner or operator of a new 

or existing cleaning operation subject to this subpart shall 

comply with the requirements in these paragraphs (a)(1) through 

(4) of this section unless the cleaning solvent used is 

identified in Table 1 of this section or contains HAP and VOC 

below the de minimis levels specified in § 63.741(f).

(1) Unless the owner or operator satisfies the requirements 

in paragraph (a)(4) of this section, place used solvent-laden 

cloth, paper, or any other absorbent applicators used for 

cleaning in bags or other closed containers. Ensure that these 

bags and containers are kept closed at all times except when 
Page 32 of 174

depositing or removing these materials from the container. Use 

bags and containers of such design so as to contain the vapors 

of the cleaning solvent. Cotton-tipped swabs used for very small 

cleaning operations are exempt from this requirement.

(2) Unless the owner or operator satisfies the requirements 

in paragraph (a)(4) of this section, store fresh and spent 

cleaning solvents, except semi-aqueous solvent cleaners, used in 

aerospace cleaning operations in closed containers.

(3) Conduct the handling and transfer of cleaning solvents 

to or from enclosed systems, vats, waste containers, and other 

cleaning operation equipment that hold or store fresh or spent 

cleaning solvents in such a manner that minimizes spills.

(4) Demonstrate to the Administrator (or delegated State, 

local, or Tribal authority) that equivalent or better 

alternative measures are in place compared to the use of closed 

containers for the solvent-laden materials described in 

paragraph (a)(1) of this section, or the storage of solvents 

described in paragraph (a)(2) of this section.

(3) Conduct the handling and transfer of cleaning solvents 

to or from enclosed systems, vats, waste containers, and other 

cleaning operation equipment that hold or store fresh or spent 

cleaning solvents in such a manner that minimizes spills.

(b) Hand-wipe cleaning. Each owner or operator of a new or 

existing hand-wipe cleaning operation (excluding cleaning of 
Page 33 of 174

spray gun equipment performed in accordance with paragraph (c) 

of this section) subject to this subpart shall use cleaning 

solvents that meet one of the requirements specified in 

paragraphs (b)(1), (b)(2), and (b)(3) of this section. Cleaning 

solvent solutions that contain HAP and VOC below the de minimis 

levels specified in §63.741(f) are exempt from the requirements 

in paragraphs (b)(1), (b)(2), and (b)(3) of this section.

(1) Meet one of the composition requirements in Table 1 of 

this section;

(2) Have a composite vapor pressure of 45 mm Hg (24.1 in. H2

O) or less at 20 °C (68 °F); or

(3) Demonstrate that the volume of hand-wipe solvents used 

in cleaning operations has been reduced by at least 60% from a 

baseline adjusted for production. The baseline shall be 

established as part of an approved alternative plan administered 

by the State. Demonstrate that the volume of hand-wipe cleaning 

solvents used in cleaning operations has been reduced by at 

least 60 percent from a baseline adjusted for production. The 

baseline shall be calculated using data from 1996 and 1997, or 

as otherwise agreed upon by the Administrator or delegated State 

Authority. The baseline shall be approved by the Administrator 

or delegated State Authority and shall be included as part of 

the facility's title V or part 70 permit.
Page 34 of 174

(c) Spray gun cleaning. Each owner or operator of a new or 

existing spray gun cleaning operation subject to this subpart in 

which spray guns are used for the application of coatings or any 

other materials that require the spray guns to be cleaned shall 

use one or more of the techniques, or their equivalent, 

specified in paragraphs (c)(1) through (c)(4) of this section. 

Spray gun cleaning operations using cleaning solvent solutions 

that contain HAP and VOC below the de minimis levels specified 

in §63.741(f) are exempt from the requirements in paragraphs 

(c)(1) through (c)(4) of this section.

(1)(i) Enclosed system. Clean the spray gun in an enclosed 

system that is closed at all times except when inserting or 

removing the spray gun. Cleaning shall consist of forcing 

solvent through the gun.

(ii) If leaks are found during the monthly inspection 

required in §63.751(a), repairs shall be made as soon as 

practicable, but no later than 15 days after the leak was found. 

If the leak is not repaired by the 15th day after detection, the 

cleaning solvent shall be removed, and the enclosed cleaner 

shall be shut down until the leak is repaired or its use is 

permanently discontinued.

(2) Nonatomized cleaning. Clean the spray gun by placing 

cleaning solvent in the pressure pot and forcing it through the 

gun with the atomizing cap in place. No atomizing air is to be 
Page 35 of 174

used. Direct the cleaning solvent from the spray gun into a vat, 

drum, or other waste container that is closed when not in use.

(3) Disassembled spray gun cleaning. Disassemble the spray 

gun and clean the components by hand in a vat, which shall 

remain closed at all times except when in use. Alternatively, 

soak the components in a vat, which shall remain closed during 

the soaking period and when not inserting or removing 

components.

(4) Atomizing cleaning. Clean the spray gun by forcing the 

cleaning solvent through the gun and direct the resulting 

atomized spray into a waste container that is fitted with a 

device designed to capture the atomized cleaning solvent 

emissions.

(5) Cleaning of the nozzle tips of automated spray 

equipment systems, except for robotic systems that can be 

programmed to spray into a closed container, shall be exempt 

from the requirements of paragraph (c) of this section.

(d) Flush cleaning. Each owner or operator of a flush 

cleaning operation subject to this subpart (excluding those in 

which Table 1 or semi-aqueous cleaning solvents are used) shall 

empty the used cleaning solvent each time aerospace parts or 

assemblies, or components of a coating unit (with the exception 

of spray guns) are flush cleaned into an enclosed container or 
Page 36 of 174

collection system that is kept closed when not in use or into a 

system with equivalent emission control.

(e) Exempt cleaning operations. The following cleaning 

operations are exempt from the requirements of paragraph (b) of 

this section: 

(1) Cleaning during the manufacture, assembly, 

installation, maintenance, or testing of components of breathing 

oxygen systems that are exposed to the breathing oxygen;

(2) Cleaning during the manufacture, assembly, 

installation, maintenance, or testing of parts, subassemblies, 

or assemblies that are exposed to strong oxidizers or reducers 

(e.g., nitrogen tetroxide, liquid oxygen, or hydrazine);

(3) Cleaning and surface activation prior to adhesive 

bonding; 

(4) Cleaning of electronic parts and assemblies containing 

electronic parts;

(5) Cleaning of aircraft and ground support equipment fluid 

systems that are exposed to the fluid, including air-to-air heat 

exchangers and hydraulic fluid systems; 

(6) Cleaning of fuel cells, fuel tanks, and confined 

spaces; 

(7) Surface cleaning of solar cells, coated optics, and 

thermal control surfaces; 
Page 37 of 174

(8) Cleaning during fabrication, assembly, installation, 

and maintenance of upholstery, curtains, carpet, and other 

textile materials used in the interior of the aircraft; 

(9) Cleaning of metallic and nonmetallic materials used in 

honeycomb cores during the manufacture or maintenance of these 

cores, and cleaning of the completed cores used in the 

manufacture of aerospace vehicles or components;

(10) Cleaning of aircraft transparencies, polycarbonate, or 

glass substrates;

(11) Cleaning and cleaning solvent usage associated with 

research and development, quality control, and laboratory 

testing;

(12) Cleaning operations, using nonflamable liquids, 

conducted within five feet of energized electrical systems. 

Energized electrical systems means any AC or DC electrical 

circuit on an assembled aircraft once electrical power is 

connected, including interior passenger and cargo areas, wheel 

wells and tail sections; and

(13) Cleaning operations identified as essential uses under 

the Montreal Protocol for which the Administrator has allocated 

essential use allowances or exemptions in 40 CFR 82.4.

Table 1—Composition Requirements for Approved Cleaning Solvents

Cleaning 

solvent type Composition requirements
Page 38 of 174

Aqueous Cleaning solvents in which water is the primary 

ingredient (≥80 percent of cleaning solvent 

solution as applied must be water). Detergents, 

surfactants, and bioenzyme mixtures and nutrients 

may be combined with the water along with a variety 

of additives, such as organic solvents (e.g., high 

boiling point alcohols), builders, saponifiers, 

inhibitors, emulsifiers, pH buffers, and 

antifoaming agents. Aqueous solutions must have a 

flash point greater than 93 °C (200 °F) (as 

reported by the manufacturer), and the solution 

must be miscible with water.

HydrocarbonbasedCleaners that are composed of photochemically 

reactive hydrocarbons and/or oxygenated 

hydrocarbons and have a maximum vapor pressure of 7 

mm Hg at 20 °C (3.75 in. H2O and 68 °F). These 

cleaners also contain no HAP.

§ 63.745 Standards: Primer and, topcoat, and specialty coating

application operations.

(a) Each owner or operator of a new or existing primer or, 

topcoat, or specialty coating application operation subject to 

this subpart shall comply with the requirements specified in 

paragraph (c) of this section for those coatings that are 

uncontrolled (no control device is used to reduce organic HAP 

emissions from the operation), and in paragraph (d) of this 

section for those coatings that are controlled (organic HAP 

emissions from the operation are reduced by the use of a control 

device). Aerospace equipment that is no longer operational, 

intended for public display, and not easily capable of being 

moved is exempt from the requirements of this section. 
Page 39 of 174

(b) Each owner or operator shall conduct the handling and 

transfer of primers and, topcoats, and specialty coatings to or 

from containers, tanks, vats, vessels, and piping systems in 

such a manner that minimizes spills. 

(c) Uncontrolled coatings—organic HAP and VOC content 

levels. Each owner or operator shall comply with the organic HAP 

and VOC content limits specified in paragraphs (c)(1) through 

(c)(46) of this section for those coatings that are 

uncontrolled. 

(1) Organic HAP emissions from primers shall be limited to 

an organic HAP content level of no more than: 540 g/L (4.5 

lb/gal) of primer (less water), as applied, for general aviation 

rework facilities; or 650 g/L (5.4 lb/gal) of exterior primer 

(less water), as applied, to large commercial aircraft 

components (parts or assemblies) or fully assembled, large 

commercial aircraft at existing affected sources that produce 

fully assembled, large commercial aircraft; or 350 g/L (2.9 

lb/gal) of primer (less water), as applied. 

(2) VOC emissions from primers shall be limited to a VOC 

content level of no more than: 540 g/L (4.5 lb/gal) of primer 

(less water and exempt solvents), as applied, for general 

aviation rework facilities; or 650 g/L (5.4 lb/gal) of exterior 

primer (less water and exempt solvents), as applied, to large 

commercial aircraft components (parts or assemblies) or fully 
Page 40 of 174

assembled, large commercial aircraft at existing affected 

sources that produce fully assembled, large commercial aircraft; 

or 350 g/L (2.9 lb/gal) of primer (less water and exempt 

solvents), as applied.

(3) Organic HAP emissions from topcoats shall be limited to 

an organic HAP content level of no more than: 420 g/L (3.5 

lb/gal) of coating (less water) as applied or 540 g/L (4.5 

lb/gal) of coating (less water) as applied for general aviation 

rework facilities. Organic HAP emissions from self-priming 

topcoats shall be limited to an organic HAP content level of no 

more than: 420 g/L (3.5 lb/gal) of self-priming topcoat (less 

water) as applied or 540 g/L (4.5 lb/gal) of self-priming 

topcoat (less water) as applied for general aviation rework 

facilities.

(4) VOC emissions from topcoats shall be limited to a VOC 

content level of no more than: 420 g/L (3.5 lb/gal) of coating 

(less water and exempt solvents) as applied or 540 g/L (4.5 

lb/gal) of coating (less water and exempt solvents) as applied 

for general aviation rework facilities. VOC emissions from selfpriming topcoats shall be limited to a VOC content level of no 

more than: 420 g/L (3.5 lb/gal) of self-priming topcoat (less 

water and exempt solvents) as applied or 540 g/L (4.5 lb/gal) of 

self-priming topcoat (less water) as applied for general 

aviation rework facilities.
Page 41 of 174

(5) Organic HAP emissions from specialty coatings shall be 

limited to an organic HAP content level of no more than the HAP 

content limit specified in Table 1 of this section for each 

applicable specialty coating type.

(6) VOC emissions from specialty coatings shall be limited 

to a VOC content level of no more than the VOC content limit 

specified in Table 1 of this section for each applicable 

specialty coating type.

Table 1. Specialty Coatings -- HAP and VOC Content Limits

Coating Type

HAP Limit

g/L 

(lb/gallon)1

VOC Limit

g/L 

(lb/gallon)1

Ablative Coating 600 (5.0) 600 (5.0)

Adhesion Promoter 890 (7.4) 890 (7.4)

Adhesive Bonding Primers: Cured 

at 250°F or below

850 (7.1) 850 (7.1)

Adhesive Bonding Primers: Cured 

above 250°F

1030 (8.6) 1030 (8.6)

Commercial Interior Adhesive 760 (6.3) 760 (6.3)

Cyanoacrylate Adhesive 1,020 (8.5) 1,020 (8.5)

Fuel Tank Adhesive 620 (5.2) 620 (5.2)

Nonstructural Adhesive 360 (3.0) 360 (3.0)

Rocket Motor Bonding Adhesive 890 (7.4) 890 (7.4)

Rubber-based Adhesive 850 (7.1) 850 (7.1)

Structural Autoclavable

Adhesive

60 (0.5) 60 (0.5)

Structural Nonautoclavable 

Adhesive

850 (7.1) 850 (7.1)

Antichafe Coating 660 (5.5) 660 (5.5)

Bearing Coating 620 (5.2) 620 (5.2)

Caulking and Smoothing 

Compounds

850 (7.1) 850 (7.1)

Chemical Agent-Resistant 

Coating

550 (4.6) 550 (4.6)

Clear Coating 720 (6.0) 720 (6.0)

Commercial Exterior Aerodynamic 

Structure Primer

650 (5.4) 650 (5.4)
Page 42 of 174

Coating Type

HAP Limit

g/L 

(lb/gallon)1

VOC Limit

g/L 

(lb/gallon)1

Compatible Substrate Primer 780 (6.5) 780 (6.5)

Corrosion Prevention Compound 710 (5.9) 710 (5.9)

Cryogenic Flexible Primer 645 (5.4) 645 (5.4)

Cryoprotective Coating 600 (5.0) 600 (5.0)

Dry Lubricative Material 880 (7.3) 880 (7.3)

Electric or Radiation-Effect 

Coating

800 (6.7) 800 (6.7)

Electrostatic Discharge and 

Electromagnetic Interference 

(EMI) Coating

800 (6.7) 800 (6.7)

Elevated-Temperature SkydrolResistant Commercial Primer740 (6.2) 740 (6.2)

Epoxy Polyamide Topcoat 660 (5.5) 660 (5.5)

Fire-Resistant (interior) 

Coating

800 (6.7) 800 (6.7)

Flexible Primer 640 (5.3) 640 (5.3)

Flight-Test Coatings: Missile 

or Single Use Aircraft

420 (3.5) 420 (3.5)

Flight-Test Coatings: All Other 840 (7.0) 840 (7.0)

Fuel-Tank Coating 720 (6.0) 720 (6.0)

High-Temperature Coating 850 (7.1) 850 (7.1)

Insulation Covering 740 (6.2) 740 (6.2)

Intermediate Release Coating 750 (6.3) 750 (6.3)

Lacquer 830 (6.9) 830 (6.9)

Bonding Maskant 1,230 (10.3) 1,230 (10.3)

Critical Use and Line Sealer 

Maskant

1,020 (8.5) 1,020 (8.5)

Seal Coat Maskant 1,230 (10.3) 1,230 (10.3)

Metallized Epoxy Coating 740 (6.2) 740 (6.2)

Mold Release 780 (6.5) 780 (6.5)

Optical Anti-Reflective Coating 750 (6.3) 750 (6.3)

Part Marking Coating 850 (7.1) 850 (7.1)

Pretreatment Coating 780 (6.5) 780 (6.5)

Rain Erosion-Resistant Coating 850 (7.1) 850 (7.1)

Rocket Motor Nozzle Coating 660 (5.5) 660 (5.5)

Scale Inhibitor 880 (7.3) 880 (7.3)

Screen Print Ink 840 (7.0) 840 (7.0)

Extrudable/Rollable/Brushable 

Sealant

280 (2.3) 280 (2.3)

Sprayable Sealant 600 (5.0) 600 (5.0)

Silicone Insulation Material 850 (7.1) 850 (7.1)
Page 43 of 174

Coating Type

HAP Limit

g/L 

(lb/gallon)1

VOC Limit

g/L 

(lb/gallon)1

Solid Film Lubricant 880 (7.3) 880 (7.3)

Specialized Function Coating 890 (7.4) 890 (7.4)

Temporary Protective Coating 320 (2.7) 320 (2.7)

Thermal Control Coating 800 (6.7) 800 (6.7)

Wet Fastener Installation 

Coating

675 (5.6) 675 (5.6)

Wing Coating 850 (7.1) 850 (7.1)

1 Coating limits for HAP are expressed in terms of mass (grams or 

pounds) of HAP per volume (liters or gallons) of coating less 

water. Coating limits for VOC are expressed in terms of mass 

(grams or pounds) of VOC per volume (liters or gallons) of 

coating less water and less exempt solvent.

(d) Controlled coatings—control system requirements. Each 

control system shall reduce the operation's organic HAP and VOC 

emissions to the atmosphere by 81% or greater, taking into 

account capture and destruction or removal efficiencies, as 

determined using the procedures in §63.750(g) when a carbon 

adsorber is used and in §63.750(h) when a control device other 

than a carbon adsorber is used. 

(e) Compliance methods. Compliance with the organic HAP and 

VOC content limits specified in paragraphs (c)(1) through 

(c)(46) of this section shall be accomplished by using the 

methods specified in paragraphs (e)(1) and (e)(2) of this 

section either by themselves or in conjunction with one another. 

(1) Use primers and, topcoats (including self-priming 

topcoats), and specialty coatings with HAP and VOC content 
Page 44 of 174

levels equal to or less than the limits specified in paragraphs 

(c)(1) through (c)(46) of this section; or

(2) Use the averaging provisions described in §63.743(d).

(f) Application equipment. Except as provided in paragraph 

(f)(3) of this section, each owner or operator of a new or 

existing primer or, topcoat (including self-priming topcoat), or 

specialty coating application operation subject to this subpart 

in which any of the coatings contain organic HAP or VOC shall 

comply with the requirements specified in paragraphs (f)(1) and 

(f)(2) of this section.

(1) All primers and, topcoats (including self-priming 

topcoats), and specialty coatings shall be applied using one or 

more of the application techniques specified in paragraphs 

(f)(1)(i) through (f)(1)(ix) of this section. 

(i) Flow/curtain coat application; 

(ii) Dip coat application; 

(iii) Roll coating; 

(iv) Brush coating; 

(v) Cotton-tipped swab application; 

(vi) Electrodeposition (dip) coating; 

(vii) High volume low pressure (HVLP) spraying; 

(viii) Electrostatic spray application; or 

(ix) Other coating application methods that achieve 

emission reductions equivalent to HVLP or electrostatic spray 
Page 45 of 174

application methods, as determined according to the requirements 

in §63.750(i). 

(2) All application devices used to apply primers or,

topcoats (including self-priming topcoats), or specialty 

coatings shall be operated according to company procedures, 

local specified operating procedures, and/or the manufacturer's 

specifications, whichever is most stringent, at alltimesall 

times. Equipment modified by the facility shall maintain a 

transfer efficiency equivalent to HVLP and electrostatic spray 

application techniques. 

(3) The following situations are exempt from the 

requirements of paragraph (f)(1) of this section: 

(i) Any situation that normally requires the use of an 

airbrush or an extension on the spray gun to properly reach 

limited access spaces; 

(ii) The application of coatings that contain fillers that 

adversely affect atomization with HVLP spray guns and that the 

permitting agency has determined cannot be applied by any of the 

application methods specified in paragraph (f)(1) of this 

section; 

(iii) The application of coatings that normally have a 

dried film thickness of less than 0.0013 centimeter (0.0005 in.) 

and that the permitting agency has determined cannot be applied 
Page 46 of 174

by any of the application methods specified in paragraph (f)(1) 

of this section; 

(iv) The use of airbrush application methods for 

stenciling, lettering, and other identification markings; 

(v) The use of hand-held spray can application methods; and 

(vi) Touch-up and repair operations. 

(g) Inorganic HAP emissions. Except as provided in 

paragraph (g)(4) of this section, each owner or operator of a 

new or existing primer or, topcoat, or specialty coating

application operation subject to this subpart in which any of 

the coatings that are spray applied contain inorganic HAP, shall

comply with the applicable requirements in paragraphs (g)(1) 

through (g)(3) of this section. 

(1) Apply these coatings in a booth or hangar in which air 

flow is directed downward onto or across the part or assembly 

being coated and exhausted through one or more outlets. 

(2) Control the air stream from this operation as follows: 

(i) For existing sources, the owner or operator must choose 

one of the following:

(A) Before exhausting it to the atmosphere, pass the air 

stream through a dry particulate filter system certified using 

the methods described in §63.750(o) to meet or exceed the 

efficiency data points in Tables 12 and 23 of this section; or
Page 47 of 174

Table 12—Two-Stage Arrestor; Liquid Phase Challenge for Existing 

Sources

Filtration efficiency requirement, % Aerodynamic particle size range, μm

>90 >5.7

>50 >4.1

>10 >2.2

Table 23—Two-Stage Arrestor; Solid Phase Challenge for Existing 

Sources

Filtration efficiency requirement, % Aerodynamic particle size range, μm

>90 >8.1

>50 >5.0

>10 >2.6

(B) Before exhausting it to the atmosphere, pass the air 

stream through a waterwash system that shall remain in operation 

during all coating application operations; or

(C) Before exhausting it to the atmosphere, pass the air 

stream through an air pollution control system that meets or 

exceeds the efficiency data points in Tables 12 and 23 of this 

section and is approved by the permitting authority.

(ii) For new sources, either:

(A) Before exhausting it to the atmosphere, pass the air 

stream through a dry particulate filter system certified using 

the methods described in §63.750(o) to meet or exceed the 

efficiency data points in Tables 34 and 45 of this section; or

Table 34—Three-Stage Arrestor; Liquid Phase Challenge for New 

Sources

Filtration efficiency requirement, % Aerodynamic particle size range, μm 
Page 48 of 174

>95 >2.0

>80 >1.0

>65 >0.42

Table 45—Three-Stage Arrestor; Solid Phase Challenge for New 

Sources

Filtration efficiency requirement, % Aerodynamic particle size range, μm

>95 >2.5

>85 >1.1

>75 >0.70

(B) Before exhausting it to the atmosphere, pass the air 

stream through an air pollution control system that meets or 

exceeds the efficiency data points in Tables 34 and 45 of this 

section and is approved by the permitting authority.

(iii) Owners or operators of new sources that have 

commenced construction or reconstruction after June 6, 1994 but 

prior to October 29, 1996 may comply with the following 

requirements in lieu of the requirements in paragraph (g)(2)(ii) 

of this section:

(A) Pass the air stream through either a two-stage dry 

particulate filter system or a waterwash system before 

exhausting it to the atmosphere.

(B) If the primer or, topcoat, or specialty coating

contains chromium or cadmium, control shall consist of a HEPA 

filter system, three-stage filter system, or other control 
Page 49 of 174

system equivalent to the three stage filter system as approved 

by the permitting agency.

(iv) If a dry particulate filter system is used, the 

following requirements shall be met:

(A) Maintain the system in good working order;

(B) Install a differential pressure gauge across the filter 

banks;

(C) Continuously monitor the pressure drop across the 

filter and read and record the pressure drop once per shift; and

(D) Take corrective action when the pressure drop exceeds 

or falls below the filter manufacturer's recommended limit(s).

(v) If a conventional waterwash system is used, 

continuously monitor the water flow rate and read and record the 

water flow rate once per shift. If a pumpless system is used, 

continuously monitor the booth parameter(s) that indicate 

performance of the booth per the manufacturer's recommendations 

to maintain the booth within the acceptable operating efficiency 

range and read and record the parameters once per shift.

(3) If the pressure drop across the dry particulate filter 

system, as recorded pursuant to §63.752(d)(1), is outside the 

limit(s) specified by the filter manufacturer or in locally 

prepared operating procedures, shut down the operation 

immediately and take corrective action. If the water path in the 

waterwash system fails the visual continuity/flow 
Page 50 of 174

characteristics check, or the water flow rate recorded pursuant 

to §63.752(d)(2) exceeds the limit(s) specified by the booth 

manufacturer or in locally prepared operating procedures, or the 

booth manufacturer's or locally prepared maintenance procedures 

for the filter or waterwash system have not been performed as 

scheduled, shut down the operation immediately and take 

corrective action. The operation shall not be resumed until the 

pressure drop or water flow rate is returned within the 

specified limit(s). 

(4) The requirements of paragraphs (g)(1) through (g)(3) of 

this section do not apply to the following: 

(i) Touch-up of scratched surfaces or damaged paint; 

(ii) Hole daubing for fasteners; 

(iii) Touch-up of trimmed edges; 

(iv) Coating prior to joining dissimilar metal components; 

(v) Stencil operations performed by brush or air brush; 

(vi) Section joining; 

(vii) Touch-up of bushings and other similar parts; 

(viii) Sealant detackifying;

(ix) Painting parts in an area identified in a title V 

permit, where the permitting authority has determined that it is 

not technically feasible to paint the parts in a booth; and 

(x) The use of hand-held spray can application methods.

§ 63.746 Standards: Depainting operations.
Page 51 of 174

(a) Applicability. Each owner or operator of a new or 

existing depainting operation subject to this subpart shall 

comply with the requirements in paragraphs (a)(1) through (a)(3) 

of this section, and with the requirements specified in 

paragraph (b) where there are no controls for organic HAP, or 

paragraph (c) where organic HAP are controlled using a control 

system. This section does not apply to an aerospace 

manufacturing or rework facility that depaints six or less 

completed aerospace vehicles in a calendar year.

(1) The provisions of this section apply to the depainting 

of the outer surface areas of completed aerospace vehicles, 

including the fuselage, wings, and vertical and horizontal 

stabilizers of the aircraft, and the outer casing and 

stabilizers of missiles and rockets. These provisions do not 

apply to the depainting of parts or units normally removed from 

the aerospace vehicle for depainting. However, depainting of 

wings and stabilizers is always subject to the requirements of 

this section regardless of whether their removal is considered 

by the owner or operator to be normal practice for depainting. 

(2) Aerospace vehicles or components that are intended for 

public display, no longer operational, and not easily capable of 

being moved are exempt from the requirements of this section. 

(3) The following depainting operations are exempt from the 

requirements of this section: 
Page 52 of 174

(i) Depainting of radomes; and

(ii) Depainting of parts, subassemblies, and assemblies 

normally removed from the primary aircraft structure before 

depainting. 

(b)(1) HAP emissions—non-HAP chemical strippers and 

technologies. Except as provided in paragraphs (b)(2) and (b)(3) 

of this section, each owner or operator of a new or existing 

aerospace depainting operation subject to this subpart shall 

emit no organic HAP from chemical stripping formulations and 

agents or chemical paint softeners.

(2) Where non-chemical based equipment is used to comply 

with paragraph (b)(1) of this section, either in total or in 

part, each owner or operator shall operate and maintain the 

equipment according to the manufacturer's specifications or 

locally prepared operating procedures. During periods of 

malfunctions of such equipment, each owner or operator may use 

substitute materials during the repair period provided the 

substitute materials used are those available that minimize 

organic HAP emissions. In no event shall substitute materials be 

used for more than 15 days annually, unless such materials are 

organic HAP-free. 

(3) Each owner or operator of a new or existing depainting 

operation shall not, on an annual average basis, use more than 

26 gallons of organic HAP-containing chemical strippers or 
Page 53 of 174

alternatively 190 pounds of organic HAP per commercial aircraft 

depainted; or more than 50 gallons of organic HAP-containing 

chemical strippers or alternatively 365 pounds of organic HAP 

per military aircraft depainted for spot stripping and decal 

removal.

(4) Each owner or operator of a new or existing depainting 

operation complying with paragraph (b)(2), that generates 

airborne inorganic HAP emissions from dry media blasting 

equipment, shall also comply with the requirements specified in 

paragraphs (b)(4)(i) through (b)(4)(v) of this section. 

(i) Perform the depainting operation in an enclosed area, 

unless a closed-cycle depainting system is used.

(ii)(A) For existing sources, pass any air stream removed 

from the enclosed area or closed-cycle depainting system through 

a dry particulate filter system, certified using the method 

described in § 63.750(o) to meet or exceed the efficiency data 

points in Tables 12 and 23 of § 63.745, through a baghouse, or 

through a waterwash system before exhausting it to the 

atmosphere.

(B) For new sources, pass any air stream removed from the 

enclosed area or closed-cycle depainting system through a dry 

particulate filter system certified using the method described 

in §63.750(o) to meet or exceed the efficiency data points in
Page 54 of 174

Tables 34 and 45 of § 63.745 or through a baghouse before 

exhausting it to the atmosphere.

(c) Owners or operators of new sources that have commenced 

construction or reconstruction after June 6, 1994 but prior to 

October 29, 1996 may comply with the following requirements in 

lieu of the requirements in paragraph (b)(4)(ii)(B) of this 

section:

(1) Pass the air stream through either a two-stage dry 

particulate filter system or a waterwash system before 

exhausting it to the atmosphere.

(2) If the coating being removed contains chromium or 

cadmium, control shall consist of a HEPA filter system, threestage filter system, or other control system equivalent to the 

three-stage filter system as approved by the permitting agency.

(iii) If a dry particulate filter system is used, the 

following requirements shall be met: 

(A) Maintain the system in good working order; 

(B) Install a differential pressure gauge across the filter 

banks; 

(C) Continuously monitor the pressure drop across the 

filter, and read and record the pressure drop once per shift; 

and

(D) Take corrective action when the pressure drop exceeds 

or falls below the filter manufacturer's recommended limits. 
Page 55 of 174

(iv) If a waterwash system is used, continuously monitor 

the water flow rate, and read and record the water flow rate 

once per shift.

(v) If the pressure drop, as recorded pursuant to 

§63.752(e)(7), is outside the limit(s) specified by the filter 

manufacturer or in locally prepared operating procedures, 

whichever is more stringent, shut down the operation immediately 

and take corrective action. If the water path in the waterwash 

system fails the visual continuity/flow characteristics check, 

as recorded pursuant to §63.752(e)(7), or the water flow rate, 

as recorded pursuant to §63.752(d)(2), exceeds the limit(s) 

specified by the booth manufacturer or in locally prepared 

operating procedures, or the booth manufacturer's or locally 

prepared maintenance procedures for the filter or waterwash 

system have not been performed as scheduled, shut down the 

operation immediately and take corrective action. The operation 

shall not be resumed until the pressure drop or water flow rate 

is returned within the specified limit(s). 

(5) Mechanical and hand sanding operations are exempt from 

the requirements in paragraph (b)(4) of this section. 

(c) Organic HAP emissions—organic HAP-containing chemical 

strippers. Each owner or operator of a new or existing organic 

HAP-containing chemical stripper depainting operation subject to 
Page 56 of 174

this subpart shall comply with the requirements specified in 

this paragraph. 

(1) All organic HAP emissions from the operation shall be 

reduced by the use of a control system. Each control system that 

was installed before the effective date shall reduce the 

operations' organic HAP emissions to the atmosphere by 81 

percent or greater, taking into account capture and destruction 

or removal efficiencies.

(2) Each control system installed on or after the effective 

date shall reduce organic HAP emissions to the atmosphere by 95 

percent or greater. Reduction shall take into account capture 

and destruction or removal efficiencies, and may take into 

account the volume of chemical stripper used relative to 

baseline levels (e.g., the 95 percent efficiency may be achieved 

by controlling emissions at 81 percent efficiency with a control 

system and using 74 percent less stripper than in baseline 

applications). The baseline shall be calculated using data from 

1996 and 1997, which shall be on a usage per aircraft or usage 

per square foot of surface basis.

(3) The capture and destruction or removal efficiencies are 

to be determined using the procedures in §63.750(g) when a 

carbon adsorber is used and those in §63.750(h) when a control 

device other than a carbon adsorber is used.
Page 57 of 174

§ 63.747 Standards: Chemical milling maskant application 

operations.

(a) Each owner or operator of a new or existing chemical 

milling maskant operation subject to this subpart shall comply 

with the requirements specified in paragraph (c) of this section 

for those chemical milling maskants that are uncontrolled (no 

control device is used to reduce organic HAP emissions from the 

operation) and in paragraph (d) of this section for those 

chemical milling maskants that are controlled (organic HAP 

emissions from the operation are reduced by the use of a control 

device). 

(b) Each owner or operator shall conduct the handling and 

transfer of chemical milling maskants to or from containers, 

tanks, vats, vessels, and piping systems in such a manner that 

minimizes spills. 

(c) Uncontrolled maskants—organic HAP and VOC content 

levels. Each owner or operator shall comply with the organic HAP 

and VOC content limits specified in paragraphs (c)(1) and (c)(2) 

of this section for each chemical milling maskant that is 

uncontrolled. 

(1) Organic HAP emissions from chemical milling maskants 

shall be limited to organic HAP content levels of no more than 

622 grams of organic HAP per liter (5.2 lb/gal) of Type I 

chemical milling maskant (less water) as applied, and no more 
Page 58 of 174

than 160 grams of organic HAP per liter (1.3 lb/gal) of Type II 

chemical milling maskant (less water) as applied.

(2) VOC emissions from chemical milling maskants shall be 

limited to VOC content levels of no more than 622 grams of VOC 

per liter (5.2 lb/gal) of Type I chemical milling maskant (less 

water and exempt solvents) as applied, and no more than 160 

grams of VOC per liter (1.3 lb/gal) of Type II chemical milling 

maskant (less water and exempt solvents) as applied.

(3) The requirements of paragraphs (c)(1) and (c)(2) of 

this section do not apply to the following: 

(i) Touch-up of scratched surfaces or damaged maskant; and 

(ii) Touch-up of trimmed edges. 

(d) Controlled maskants—control system requirements. Each

control system shall reduce the operation's organic HAP and VOC 

emissions to the atmosphere by 81% or greater, taking into 

account capture and destruction or removal efficiencies, as 

determined using the procedures in §63.750(g) when a carbon 

adsorber is used and in §63.750(h) when a control device other 

than a carbon adsorber is used. 

(e) Compliance methods. Compliance with the organic HAP and 

VOC content limits specified in paragraphs (c)(1) and (c)(2) of 

this section may be accomplished by using the methods specified 

in paragraphs (e)(1) and (e)(2) of this section either by 

themselves or in conjunction with one another. 
Page 59 of 174

(1) Use chemical milling maskants with HAP and VOC content 

levels equal to or less than the limits specified in paragraphs 

(c)(1) and (c)(2) of this section. 

(2) Use the averaging provisions described in §63.743(d).

§ 63.748 Standards: Handling and storage of waste.

Except as provided in §63.741(e), the owner or operator of 

each facility subject to this subpart that produces a waste that 

contains HAP shall conduct the handling and transfer of the 

waste to or from containers, tanks, vats, vessels, and piping 

systems in such a manner that minimizes spills.

§ 63.749 Compliance dates and determinations.

(a) Compliance dates. (1) Each owner or operator of an 

existing affected source subject to this subpart shall comply 

with the requirements of this subpart by September 1, 1998, 

except as specified in paragraphparagraphs (a)(2) and (3) of 

this section. Owners or operators of new affected sources 

subject to this subpart shall comply on the effective date or 

upon startup, whichever is later. In addition, each owner or 

operator shall comply with the compliance dates specified in §

63.6(b) and (c).) as indicated in Table 1 to this subpart.

(2) Owners or operators of existing primer or, topcoat, or 

specialty coating application operations and depainting 

operations who construct or reconstruct a spray booth or hangar 

must comply with the new source requirements for inorganic HAP 
Page 60 of 174

specified in §§ 63.745(g)(2)(ii) and 63.746(b)(4) for that new 

spray booth or hangar upon startup. Such sources must still 

comply with all other existing source requirements by September 

1, 1998.

(3) Each owner or operator of a specialty coating 

application operation that begins construction or reconstruction 

after [insert date of publication of proposed rule in the 

Federal Register] shall be in compliance with the requirements 

of this subpart on [insert date of publication of proposed rule 

in the Federal Register] or upon startup, whichever is later. 

Each owner or operator of a specialty coating application 

operation that is existing on [insert date of publication of 

proposed rule in the Federal Register] shall be in compliance 

with the requirements of this subpart on or before [insert date 

1 year after date of publication of final rule in the Federal 

Register].

(b) General. Each facility subject to this subpart shall be 

considered in noncompliance if the owner or operator fails to 

submit a startup, shutdown, and malfunction plan as required by 

§63.743(b) or usesuse a control device other than one specified 

in this subpart that has not been approved by the Administrator, 

as required by § 63.743(c).

(c) Cleaning operations. Each cleaning operation subject to 

this subpart shall be considered in noncompliance if the owner 
Page 61 of 174

or operator fails to institute and carry out the housekeeping 

measures required under §63.744(a). Incidental emissions 

resulting from the activation of pressure release vents and 

valves on enclosed cleaning systems are exempt from this 

paragraph. 

(1) Hand-wipe cleaning. An affected hand-wipe cleaning 

operation shall be considered in compliance when all hand-wipe 

cleaning solvents, excluding those used for hand cleaning of 

spray gun equipment under §63.744(c)(3), meet either the 

composition requirements specified in §63.744(b)(1) or the vapor 

pressure requirement specified in §63.744(b)(2). 

(2) Spray gun cleaning. An affected spray gun cleaning 

operation shall be considered in compliance when each of the 

following conditions is met: 

(i) One of the four techniques specified in §63.744 (c)(1) 

through (c)(4) is used; 

(ii) The technique selected is operated according to the 

procedures specified in §63.744 (c)(1) through (c)(4) as 

appropriate; and 

(iii) If an enclosed system is used, monthly visual 

inspections are conducted and any leak detected is repaired 

within 15 days after detection. If the leak is not repaired by 

the 15th day after detection, the solvent shall be removed and 
Page 62 of 174

the enclosed cleaner shall be shut down until the cleaner is 

repaired or its use is permanently discontinued. 

(3) Flush cleaning. An affected flush cleaning operation 

shall be considered in compliance if the operating requirements 

specified in §63.744(d) are implemented and carried out. 

(d) Organic HAP and VOC content levels—primer and, topcoat, 

and specialty coating application operations—

(1) Performance test periods. For uncontrolled coatings 

that are not averaged, each 24 hours is considered a performance 

test. For compliant and non-compliant coatings that are averaged 

together, each 30-day period is considered a performance test, 

unless the permitting agency specifies a shorter averaging 

period as part of an ambient ozone control program. When using a 

control device other than a carbon adsorber, three 1-hour runs 

constitute the test period for the initial and any subsequent 

performance test. When using a carbon adsorber, each rolling 

material balance period is considered a performance test. 

(2) Initial performance tests. If a control device is used, 

each owner or operator shall conduct an initial performance test 

to demonstrate compliance with the overall reduction efficiency 

specified in paragraph §63.745, unless a waiver is obtained 

under either §63.7(e)(2)(iv) or §63.7(h). The initial 

performance test shall be conducted according to the procedures 

and test methods specified in §63.7 and §63.750(g) for carbon 
Page 63 of 174

adsorbers and in §63.750(h) for control devices other than 

carbon adsorbers. For carbon adsorbers, the initial performance 

test shall be used to establish the appropriate rolling material 

balance period for determining compliance. The procedures in 

paragraphs (d)(2)(i) through (d)(2)(vi) of this section shall be 

used in determining initial compliance with the provisions of 

this subpart for carbon adsorbers. 

(i)(A) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 

carbon adsorption system with a common exhaust stack for all the 

individual carbon adsorber vessels pursuant to §63.750(g) (2) or 

(4), the test shall consist of three separate runs, each 

coinciding with one or more complete sequences through the 

adsorption cycles of all of the individual carbon adsorber 

vessels. 

(B) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 

carbon adsorption system with individual exhaust stacks for each 

carbon adsorber vessel pursuant to §63.750(g) (3) or (4), each 

carbon adsorber vessel shall be tested individually. The test 

for each carbon adsorber vessel shall consist of three separate 

runs. Each run shall coincide with one or more complete 

adsorption cycles. 
Page 64 of 174

(ii) EPA Method 1 or 1A of appendix A of part 60 is used 

for sample and velocity traverses. 

(iii) EPA Method 2, 2A, 2C, or 2D of appendix A of part 60 

is used for velocity and volumetric flow rates. 

(iv) EPA Method 3 of appendix A of part 60 is used for gas 

analysis. 

(v) EPA Method 4 of appendix A of part 60 is used for stack 

gas moisture. 

(vi) EPA Methods 2, 2A, 2C, 2D, 3, and 4 shall be 

performed, as applicable, at least twice during each test 

period. 

(3) The primer application operation is considered in 

compliance when the conditions specified in paragraphs (d)(3)(i) 

through (d)(3)(iv) of this section, as applicable, and in 

paragraph (e) of this section are met. Failure to meet any one 

of the conditions identified in these paragraphs shall 

constitute noncompliance. 

(i) For all uncontrolled primers, all values of Hi and Ha

(as determined using the procedures specified in §63.750 (c) and 

(d)) are less than or equal to 350 grams of organic HAP per 

liter (2.9 lb/gal) of primer (less water) as applied, and all 

values of Gi and Ga (as determined using the procedures specified 

in §63.750 (e) and (f)) are less than or equal to 350 grams of 
Page 65 of 174

organic VOC per liter (2.9 lb/gal) of primer (less water and 

exempt solvents) as applied. 

(ii) If a control device is used: 

(A) The overall control system efficiency, Ek, as determined 

using the procedures specified in §63.750(g) for control systems 

containing carbon adsorbers and in §63.750(h) for control 

systems with other control devices, is equal to or greater than 

81% during the initial performance test and any subsequent 

performance test; 

(B) If an incinerator other than a catalytic incinerator is 

used, the average combustion temperature for all 3-hour periods 

is greater than or equal to the average combustion temperature 

established under §63.751(b)(11); and 

(C) If a catalytic incinerator is used, the average 

combustion temperatures for all 3-hour periods are greater than 

or equal to the average combustion temperatures established 

under §63.751(b)(12). 

(iii)(A) Uses an application technique specified in §63.745 

(f)(1)(i) through (f)(1)(viii), or 

(B) Uses an alternative application technique, as allowed 

under §63.745(f)(1)(ix), such that the emissions of both organic 

HAP and VOC for the implementation period of the alternative 

application method are less than or equal to the emissions 
Page 66 of 174

generated using HVLP or electrostatic spray application methods 

as determined using the procedures specified in §63.750(i).

(iv) Operates all application techniques in accordance with 

the manufacturer's specifications or locally prepared operating 

procedures, whichever is more stringent. 

(4) The topcoat or specialty coating application operation 

is considered in compliance when the conditions specified in 

paragraphs (ed)(4)(i) through (ed)(4)(iv) of this section, as 

applicable, and in paragraph (f) e) of this section are met. 

Failure to meet any of the conditions identified in these 

paragraphs shall constitute noncompliance. 

(i) The topcoat application operation is considered in 

compliance when the conditions specified in paragraphs 

(d)(4)(i)(A) are met. The specialty coating application 

operation is considered in compliance when the conditions 

specified in paragraphs (d)(4)(i)(B) are met.

(A) For all uncontrolled topcoats, all values of Hi and Ha

(as determined using the procedures specified in §63.750(c) and

(d)) are less than or equal to 420 grams organic HAP per liter 

(3.5 lb/gal) of topcoat (less water) as applied, and all values 

of Gi and Ga (as determined using the procedures specified in 

§63.750(e) and (f)) are less than or equal to 420 grams organic 

VOC per liter (3.5 lb/gal) of topcoat (less water and exempt 

solvents) as applied. 
Page 67 of 174

(B) For all uncontrolled specialty coatings, all values of 

Hi and Ha (as determined using the procedures specified in §

63.750 (c) and (d)) are less than or equal to the HAP content 

limits specified in Table 1 to § 63.745 for the applicable 

specialty coating types (less water) as applied, and all values 

of Gi and Ga (as determined using the procedures specified in §

63.750(e) and (f)) are less than or equal to the VOC content 

limits specified in Table 1 to § 63.745 for the applicable 

specialty coating types (less water and exempt solvents) as 

applied.

(ii) If a control device is used,

(A) The overall control system efficiency, Ek, as determined 

using the procedures specified in §63.750(g) for control systems 

containing carbon adsorbers and in §63.750(h) for control 

systems with other control devices, is equal to or greater than 

81% during the initial performance test and any subsequent 

performance test; 

(B) If an incinerator other than a catalytic incinerator is 

used, the average combustion temperature for all 3-hour periods 

is greater than or equal to the average combustion temperature 

established under §63.751(b)(11); and 

(C) If a catalytic incinerator is used, the average 

combustion temperatures for all 3-hour periods are greater than 
Page 68 of 174

or equal to the average combustion temperatures established 

under §63.751(b)(12). 

(iii)(A) Uses an application technique specified in §63.745 

(f)(1)(i) through (f)(1)(viii); or

(B) Uses an alternative application technique, as allowed 

under §63.745(f)(1)(ix), such that the emissions of both organic 

HAP and VOC for the implementation period of the alternative 

application method are less than or equal to the emissions 

generated using HVLP or electrostatic spray application methods 

as determined using the procedures specified in §63.750(i).

(iv) Operates all application techniques in accordance with 

the manufacturer's specifications or locally prepared operating 

procedures.

(e) Inorganic HAP emissions—primer and, topcoat, and 

specialty coating application operations. For each primer or,

topcoat, or specialty coating application operation that emits 

inorganic HAP, the operation is in compliance when: 

(1) It is operated according to the requirements specified 

in §63.745(g)(1) through (g)(3); and 

(2) It is shut down immediately whenever the pressure drop 

or water flow rate is outside the limit(s) established for them 

and is not restarted until the pressure drop or water flow rate 

is returned within these limit(s), as required under 

§63.745(g)(3). 
Page 69 of 174

(f) Organic HAP emissions—Depainting operations—(1) 

Performance test periods. When using a control device other than 

a carbon adsorber, three 1-hour runs constitute the test period 

for the initial and any subsequent performance test. When a 

carbon adsorber is used, each rolling material balance period is 

considered a performance test. Each 24-hour period is considered 

a performance test period for determining compliance with 

§63.746(b)(1). For uncontrolled organic emissions from 

depainting operations, each calendar year is considered a 

performance test period for determining compliance with the HAP 

limits for organic HAP-containing chemical strippers used for 

spot stripping and decal removal. 

(2) Initial performance tests. If a control device is used, 

each owner or operator shall conduct an initial performance test 

to demonstrate compliance with the overall reduction efficiency 

specified in §63.746(c), unless a waiver is obtained under 

either §63.7(e)(2)(iv) or §63.7(h). The initial performance test 

shall be conducted according to the procedures and test methods 

specified in §63.7 and §63.750(g) for carbon adsorbers and in 

§63.750(h) for control devices other than carbon adsorbers. For 

carbon adsorbers, the initial performance test shall be used to 

establish the appropriate rolling material balance period for 

determining compliance. The procedures in paragraphs (2)(i) 

through (2)(vi) of this section shall be used in determining 
Page 70 of 174

initial compliance with the provisions of this subpart for 

carbon adsorbers. 

(i)(A) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 

carbon adsorption system with a common exhaust stack for all the 

individual carbon adsorber vessels pursuant to §63.750(g)(2) or 

(4), the test shall consist of three separate runs, each 

coinciding with one or more complete sequences through the 

adsorption cycles of all of the individual carbon adsorber 

vessels. 

(B) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 

carbon adsorption system with individual exhaust stacks for each 

carbon adsorber vessel pursuant to §63.750(g) (3) or (4), each 

carbon adsorber vessel shall be tested individually. The test 

for each carbon adsorber vessel shall consist of three separate 

runs. Each run shall coincide with one or more complete 

adsorption cycles. 

(ii) EPA Method 1 or 1A of appendix A of part 60 is used 

for sample and velocity traverses. 

(iii) EPA Method 2, 2A, 2C, or 2D of appendix A of part 60 

is used for velocity and volumetric flow rates. 

(iv) EPA Method 3 of appendix A of part 60 is used for gas 

analysis. 
Page 71 of 174

(v) EPA Method 4 of appendix A of part 60 is used for stack 

gas moisture. 

(vi) EPA Methods 2, 2A, 2C, 2D, 3, and 4 shall be 

performed, as applicable, at least twice during each test 

period. 

(3) An organic HAP-containing chemical stripper depainting 

operation is considered in compliance when the conditions 

specified in paragraph (g)(3)(i) of this section are met. 

(i) If a carbon adsorber (or other control device) is used, 

the overall control efficiency of the control system, as 

determined using the procedures specified in §63.750(g) (or 

other control device as determined using the procedures 

specified in §63.750(h)), is equal to or greater than 81% for 

control systems installed before the effective date, or equal to 

or greater than 95% for control systems installed on or after 

the effective date, during the initial performance test and all 

subsequent material balances (or performance tests, as 

appropriate). 

(ii) For non-HAP depainting operations complying with 

§63.746(b)(1); 

(A) For any spot stripping and decal removal, the value of 

C, as determined using the procedures specified in §63.750(j), 

is less than or equal to 26 gallons of organic HAP-containing 

chemical stripper or 190 pounds of organic HAP per commercial 
Page 72 of 174

aircraft depainted calculated on a yearly average; and is less 

than or equal to 50 gallons of organic HAP-containing chemical 

stripper or 365 pounds of organic HAP per military aircraft 

depainted calculated on a yearly average; and

(B) The requirements of §63.746(b)(2) are carried out 

during malfunctions of non-chemical based equipment. 

(g) Inorganic HAP emissions—depainting operations. Each 

depainting operation is in compliance when: 

(1) The operating requirements specified in §63.746(b)(4) 

are followed; and 

(2) It is shut down immediately whenever the pressure drop 

or water flow rate is outside the limit(s) established for them 

and is not restarted until the pressure drop or water flow rate 

is returned within these limit(s), as required under 

§63.746(b)(4)(v). 

(h) Chemical milling maskant application operations—(1) 

Performance test periods. For uncontrolled chemical milling 

maskants that are not averaged, each 24-hour period is 

considered a performance test. For compliant and noncompliant 

chemical milling maskants that are averaged together, each 30-

day period is considered a performance test, unless the 

permitting agency specifies a shorter period as part of an 

ambient ozone control program. When using a control device other 

than a carbon adsorber, three 1-hour runs constitute the test 
Page 73 of 174

period for the initial and any subsequent performance test. When 

a carbon adsorber is used, each rolling material balance period 

is considered a performance test. 

(2) Initial performance tests. If a control device is used, 

each owner or operator shall conduct an initial performance test 

to demonstrate compliance with the overall reduction efficiency 

specified in §63.747(d), unless a waiver is obtained under 

either §63.7(e)(2)(iv) or §63.7(h). The initial performance test 

shall be conducted according to the procedures and test methods 

specified in §63.7 and §63.750(g) for carbon adsorbers and in 

§63.750(h) for control devices other than carbon adsorbers. For 

carbon adsorbers, the initial performance test shall be used to 

establish the appropriate rolling material balance period for 

determining compliance. The procedures in paragraphs (h)(2) (i) 

through (vi) of this section shall be used in determining 

initial compliance with the provisions of this subpart for 

carbon adsorbers. 

(i)(A) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 

carbon adsorption system with a common exhaust stack for all the 

individual carbon adsorber vessels pursuant to §63.750(g) (2) or 

(4), the test shall consist of three separate runs, each 

coinciding with one or more complete sequences through the 
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adsorption cycles of all of the individual carbon adsorber 

vessels. 

(B) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 

carbon adsorption system with individual exhaust stacks for each 

carbon adsorber vessel pursuant to §63.750(g) (3) or (4), each 

carbon adsorber vessel shall be tested individually. The test 

for each carbon adsorber vessel shall consist of three separate 

runs. Each run shall coincide with one or more complete 

adsorption cycles. 

(ii) EPA Method 1 or 1A of appendix A of part 60 is used 

for sample and velocity traverses. 

(iii) EPA Method 2, 2A, 2C, or 2D of appendix A of part 60 

is used for velocity and volumetric flow rates. 

(iv) EPA Method 3 of appendix A of part 60 is used for gas 

analysis. 

(v) EPA Method 4 of appendix A of part 60 is used for stack 

gas moisture. 

(vi) EPA Methods 2, 2A, 2C, 2D, 3, and 4 shall be 

performed, as applicable, at least twice during each test 

period. 

(3) The chemical milling maskant application operation is 

considered in compliance when the conditions specified in 

paragraphs (i)(3)(i) and (i)(3)(ii) of this section are met. 
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(i) For all uncontrolled chemical milling maskants, all 

values of Hi and Ha (as determined using the procedures specified 

in §63.750 (k) and (l)) are less than or equal to 622 grams of 

organic HAP per liter (5.2 lb/gal) of Type I chemical milling 

maskant as applied (less water), and 160 grams of organic HAP 

per liter (1.3 lb/gal) of Type II chemical milling maskant as 

applied (less water). All values of Gi and Ga (as determined 

using the procedures specified in §63.750 (m) and (n)) are less 

than or equal to 622 grams of VOC per liter (5.2 lb/gal) of Type 

I chemical milling maskant as applied (less water and exempt 

solvents), and 160 grams of VOC per liter (1.3 lb/gal) of Type 

II chemical milling maskant (less water and exempt solvents) as 

applied.

(ii) If a carbon adsorber (or other control device) is 

used, the overall control efficiency of the control system, as 

determined using the procedures specified in §63.750(g) (or 

systems with other control devices as determined using the 

procedures specified in §63.750(h)), is equal to or greater than 

81% during the initial performance test period and all 

subsequent material balances (or performance tests, as 

appropriate). 

(i) Handling and storage of waste. For those wastes subject 

to this subpart, failure to comply with the requirements 

specified in §63.748 shall be considered a violation. 
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(j) Performance tests shall be conducted under such 

conditions as the Administrator specifies to the owner or 

operator based on representative performance of the affected 

source for the period being tested. Representative conditions 

exclude periods of startup and shutdown unless specified by the

Administrator or an applicable subpart. The owner or operator 

may not conduct performance tests during periods of malfunction. 

The owner or operator must record the process information that 

is necessary to document operating conditions during the test 

and include in such record an explanation to support that such 

conditions represent normal operation. Upon request, the owner 

or operator shall make available to the Administrator such 

records as may be necessary to determine the conditions of 

performance tests.

§ 63.750 Test methods and procedures.

(a) Composition determination. Compliance with the handwipe cleaning solvent approved composition list specified in 

§63.744(b)(1) for hand-wipe cleaning solvents shall be 

demonstrated using data supplied by the manufacturer of the 

cleaning solvent. The data shall identify all components of the 

cleaning solvent and shall demonstrate that one of the approved 

composition definitions is met. 

(b) Vapor pressure determination. The composite vapor 

pressure of hand-wipe cleaning solvents used in a cleaning 
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operation subject to this subpart shall be determined as 

follows: 

(1) For single-component hand-wipe cleaning solvents, the 

vapor pressure shall be determined using MSDS or other 

manufacturer's data, standard engineering reference texts, or 

other equivalent methods. 

(2) The composite vapor pressure of a blended hand-wipe 

solvent shall be determined by quantifying the amount of each 

organic compound in the blend using manufacturer's supplied data 

or a gas chromatographic analysis in accordance with ASTM E 260-

91 or 96 (incorporated by reference—see §63.14 of subpart A of 

this part) and by calculating the composite vapor pressure of 

the solvent by summing the partial pressures of each component. 

The vapor pressure of each component shall be determined using 

manufacturer's data, standard engineering reference texts, or 

other equivalent methods. The following equation shall be used 

to determine the composite vapor pressure:

where: 

Wi = Weight of the “i”th VOC compound, grams.

Ww = Weight of water, grams. 

We = Weight of non-HAP, nonVOC compound, grams. 
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MWi = Molecular weight of the “i”th VOC compound, g/gmole. 

MWw = Molecular weight of water, g/g-mole. 

MWe = Molecular weight of exempt compound, g/g-mole. 

PPc = VOC composite partial pressure at 20 °C, mm Hg. 

VPi = Vapor pressure of the “i”th VOC compound at 20 °C, 

mm Hg.

(c) Organic HAP content level determination—compliant 

primers and, topcoats, and specialty coatings. For those 

uncontrolled primers and, topcoats, and specialty coatings

complying with the primer and, topcoat, or specialty coating

organic HAP content limits specified in § 63.745(c) without 

being averaged, the following procedures in paragraphs (c)(1) 

through (3) of this section shall be used to determine the mass 

of organic HAP emitted per volume of coating (less water) as 

applied. As an alternative to the procedures in paragraphs 

(c)(1) through (3) of this section, an owner or operator may use 

the coating manufacturer’s supplied data to demonstrate that 

organic HAP emitted per volume of coating (less water), as 

applied, is less than or equal to the applicable organic HAP 

limit specified in § 63.745(c). 

(1) For coatings that contain no exempt solvents, determine 

the total organic HAP content using manufacturer's supplied data 

or Method 24 of 40 CFR part 60, appendix A, to determine the VOC 

content. The VOC content shall be used as a surrogate for total 

HAP content for coatings that contain no exempt solvent. If 
Page 79 of 174

there is a discrepancy between the manufacturer's formulation 

data and the results of the Method 24 analysis, compliance shall 

be based on the results from the Method 24 analysis.

When Method 24 is used to determine the VOC content of 

water-reducible coatings, the precision adjustment factors in 

Reference Method 24 shall be used. If the adjusted analytical 

VOC content is less than the formulation solvent content, then 

the analytical VOC content should be set equal to the 

formulation solvent content. 

(2) For each coating formulation as applied, determine the 

organic HAP weight fraction, water weight fraction (if 

applicable), and density from manufacturer's data. If these 

values cannot be determined using the manufacturer's data, the 

owner or operator shall submit an alternative procedure for 

determining their values for approval by the Administrator. 

Recalculation is required only when a change occurs in the 

coating formulation. 

(3) For each coating as applied, calculate the mass of 

organic HAP emitted per volume of coating (lb/gal) less water as 

applied using equations 1, 2, and 3: 

where: 
Page 80 of 174

Vwi = volume (gal) of water in one gal of coating i. 

Dci = density (lb of coating per gal of coating) of 

coating i. 

Wwi = weight fraction (expressed as a decimal) of water in 

coating i. 

Dw = density of water, 8.33 lb/gal.

where: 

MHi = mass (lb) of organic HAP in one gal of coating i. 

Dci = density (lb of coating per gal of coating) of

coating i. 

WHi = weight fraction (expressed as a decimal) of organic 

HAP in coating i.

where: 

Hi = mass of organic HAP emitted per volume of coating i 

(lb/gal) less water as applied. 

MHi = mass (lb) of organic HAP in one gal of coating i. 

Vwi = volume (gal) of water in one gal of coating i.

(d) Organic HAP content level determination—averaged 

primers and, topcoats., and specialty coatings. For those 

uncontrolled primers and, topcoats, and specialty coatings that 

are averaged together in order to comply with the primer and,

topcoat, and specialty coating organic HAP content limits 

specified in §63.745(c), the following procedure shall be used 
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to determine the monthly volume-weighted average mass of organic 

HAP emitted per volume of coating (less water) as applied, 

unless the permitting agency specifies a shorter averaging 

period as part of an ambient ozone control program. 

(1)(i) Determine the total organic HAP weight fraction as 

applied of each coating. If any ingredients, including diluent 

solvent, are added to a coating prior to its application, the 

organic HAP weight fraction of the coating shall be determined 

at a time and location in the process after all ingredients have 

been added. 

(ii) Determine the total organic HAP weight fraction of 

each coating as applied each month. 

(A) If no changes have been made to a coating, either as 

supplied or as applied, or if a change has been made that has a 

minimal effect on the organic HAP content of the coating, the

value previously determined may continue to be used until a 

change in formulation has been made by either the manufacturer 

or the user. 

(B) If a change in formulation or a change in the 

ingredients added to the coating takes place, including the 

ratio of coating to diluent solvent, prior to its application, 

either of which results in a more than minimal effect on the 

organic HAP content of the coating, the total organic HAP weight 

fraction of the coating shall be redetermined. 
Page 82 of 174

(iii) Manufacturer's formulation data may be used to 

determine the total organic HAP content of each coating and any 

ingredients added to the coating prior to its application. If 

the total organic HAP content cannot be determined using the 

manufacturer's data, the owner or operator shall submit an 

alternative procedure for determining the total organic HAP 

weight fraction for approval by the Administrator. 

(2)(i) Determine the volume both in total gallons as 

applied and in total gallons (less water) as applied of each 

coating. If any ingredients, including diluent solvents, are 

added prior to its application, the volume of each coating shall 

be determined at a time and location in the process after all 

ingredients (including any diluent solvent) have been added. 

(ii) Determine the volume of each coating (less water) as 

applied each month, unless the permitting agency specifies a 

shorter period as part of an ambient ozone control program. 

(iii) The volume applied may be determined from company 

records. 

(3)(i) Determine the density of each coating as applied. If 

any ingredients, including diluent solvent, are added to a 

coating prior to its application, the density of the coating 

shall be determined at a time and location in the process after 

all ingredients have been added. 
Page 83 of 174

(ii) Determine the density of each coating as applied each 

month, unless the permitting agency specifies a shorter period 

as part of an ambient ozone control program. 

(A) If no changes have been made to a coating, either as 

supplied or as applied, or if a change has been made that has a 

minimal effect on the density of the coating, then the value 

previously determined may continue to be used until a change in 

formulation has been made by either the manufacturer or the 

user. 

(B) If a change in formulation or a change in the 

ingredients added to the coating takes place, including the 

ratio of coating to diluent solvent, prior to its application, 

either of which results in a more than minimal effect on the 

density of the coating, then the density of the coating shall be 

redetermined. 

(iii) The density may be determined from company records, 

including manufacturer's data sheets. If the density of the 

coating cannot be determined using the company's records, 

including the manufacturer's data, then the owner or operator 

shall submit an alternative procedure for determining the 

density for approval by the Administrator. 

(4) Calculate the total volume in gallons as applied (less 

water) by summing the individual volumes of each coating (less 
Page 84 of 174

water) as applied, which were determined under paragraph (d)(2) 

of this section. 

(5) Calculate the volume-weighted average mass of organic 

HAP in coatings emitted per unit volume (lb/gal) of coating 

(less water) as applied during each 30-day period using equation 

4:

where: 

Ha = volume-weighted average mass of organic HAP emitted 

per unit volume of coating (lb/gal) (less water) as 

applied during each 30-day period for those coatings 

being averaged. 

n = number of coatings being averaged.

WHi = weight fraction (expressed as a decimal) of organic 

HAP in coating i as applied that is being averaged 

during each 30-day period. 

Dci = density (lb of coating per gal of coating) of 

coating i as applied that is being averaged during 

each 30-day period. 

Vci = volume (gal) of coating i as applied that is being 

averaged during the 30-day period. 

Clw = total volume (gal) of all coatings (less water) as 

applied that are being averaged during each 30-day 

period.

(e) VOC content level determination—compliant primers and,

topcoats, and specialty coatings. For those uncontrolled primers

and, topcoats, and specialty coatings complying with the primer

and, topcoat, and specialty coating VOC content levels specified 
Page 85 of 174

in § 63.745(c) without being averaged, the following procedures 

in paragraphs (e)(1) through (3) of this section shall be used 

to determine the mass of VOC emitted per volume of coating (less 

water and exempt solvents) as applied. As an alternative to the 

procedures in paragraphs (e)(1) through (3) of this section, an 

owner or operator may use coating manufacturer’s supplied data 

to demonstrate that VOC emitted per volume of coating (less 

water and exempt solvents), as applied, is less than or equal to 

the applicable VOC limit specified in § 63.745(c). 

(1) Determine the VOC content of each formulation (less 

water and exempt solvents) as applied using manufacturer's 

supplied data or Method 24 of 40 CFR part 60, appendix A, to 

determine the VOC content. The VOC content shall be used as a 

surrogate for total HAP content for coatings that contain no 

exempt solvent. If there is a discrepancy between the 

manufacturer's formulation data and the results of the Method 24 

analysis, compliance shall be based on the results from the 

Method 24 analysis.

When Method 24 is used to determine the VOC content of 

water-reducible coatings, the precision adjustment factors in 

Reference Method 24 shall be used. If the adjusted analytical 

VOC content is less than the formulation solvent content, then 

the analytical VOC content should be set equal to the 

formulation solvent content. 
Page 86 of 174

(2) For each coating applied, calculate the mass of VOC 

emitted per volume of coating (lb/gal) (less water and exempt 

solvents) as applied using equations 5, 6, and 7: 

where: 

Vwi = volume (gal) of water in one gal of coating i. 

Dci = density (lb of coating per gal of coating) of 

coating i. 

Wwi = weight fraction (expressed as a decimal) of water in 

coating i. 

Dw = density of water, 8.33 lb/gal.

where: 

MVi = mass (lb) of VOC in one gal of coating i. 

Dci = density (lb of coating per gal of coating) of 

coating i. 

WVi = weight fraction (expressed as a decimal) of VOC in 

coating i.

where: 

Gi = mass of VOC emitted per volume of coating i (lb/gal) 

(less water and exempt solvents) as applied. 

MVi = mass (lb) of VOC in one gal of coating i. 

Vwi = volume (gal) of water in one gal of coating i. 
Page 87 of 174

VXi = volume (gal) of exempt solvents in one gal of 

coating i.

(3)(i) If the VOC content is found to be different when EPA 

Method 24 is used during an enforcement inspection from that 

used by the owner or operator in calculating Ga, compliance shall 

be based, except as provided in paragraph (e)(3)(ii) of this 

section, upon the VOC content obtained using EPA Method 24. 

(ii) If the VOC content of a coating obtained using Method 

24 would indicate noncompliance as determined under either 

§63.749 (d)(3)(i) or (d)(4)(i), an owner or operator may elect 

to average the coating with other uncontrolled coatings and 

(re)calculate Gi (using the procedure specified in paragraph (f) 

of this section), provided appropriate and sufficient records 

were maintained for all coatings included in the average 

(re)calculation. The (re)calculated value of Gi (Ga in paragraph 

(f)) for the averaged coatings shall then be used to determine 

compliance. 

(f) VOC content level determination—averaged primers and,

topcoats., and specialty coatings. For those uncontrolled 

primers and, topcoats, and specialty coatings that are averaged 

within their respective coating category in order to comply with 

the primer and, topcoat, and specialty coating VOC content 

limits specified in § 63.745 (c)(2), (c)(4), and (c)(46), the 

following procedure shall be used to determine the monthly 

volume-weighted average mass of VOC emitted per volume of 
Page 88 of 174

coating (less water and exempt solvents) as applied, unless the 

permitting agency specifies a shorter averaging period as part 

of an ambient ozone control program. 

(1)(i) Determine the VOC content (lb/gal) as applied of 

each coating. If any ingredients, including diluent solvent, are 

added to a coating prior to its application, the VOC content of 

the coating shall be determined at a time and location in the 

process after all ingredients have been added. 

(ii) Determine the VOC content of each coating as applied 

each month, unless the permitting agency specifies a shorter 

period as part of an ambient ozone control program. 

(A) If no changes have been made to a coating, either as 

supplied or as applied, or if a change has been made that has a 

minimal effect on the VOC content of the coating, the value 

previously determined may continue to be used until a change in 

formulation has been made by either the manufacturer or the 

user. 

(B) If a change in formulation or a change in the 

ingredients added to the coating takes place, including the 

ratio of coating to diluent solvent, prior to its application, 

either of which results in a more than minimal effect on the VOC 

content of the coating, the VOC content of the coating shall be 

redetermined. 
Page 89 of 174

(iii) Determine the VOC content of each primer and,

topcoat, and specialty coating formulation (less water and 

exempt solvents) as applied using EPA Method 24 or from 

manufacturer's data. 

(2)(i) Determine the volume both in total gallons as 

applied and in total gallons (less water and exempt solvents) as 

applied of each coating. If any ingredients, including diluent 

solvents, are added prior to its application, the volume of each 

coating shall be determined at a time and location in the 

process after all ingredients (including any diluent solvent) 

have been added. 

(ii) Determine the volume of each coating (less water and 

exempt solvents) as applied each day. 

(iii) The volume applied may be determined from company 

records. 

(3) Calculate the total volume in gallons (less water and 

exempt solvents) as applied by summing the individual volumes of 

each coating (less water and exempt solvents) as applied, which 

were determined under paragraph (f)(2) of this section. 

(4) Calculate the volume-weighted average mass of VOC 

emitted per unit volume (lb/gal) of coating (less water and 

exempt solvents) as applied for each coating category during 

each 30-day period using equation 8: 
Page 90 of 174

where: 

Ga = volume weighted average mass of VOC per unit volume 

of coating (lb/gal) (less water and exempt solvents) 

as applied during each 30-day period for those 

coatings being averaged. 

n = number of coatings being averaged. 

(VOC)ci = VOC content (lb/gal) of coating i (less water and 

exempt solvents) as applied (as determined using the 

procedures specified in paragraph (f)(1) of this 

section) that is being averaged during the 30-day 

period. 

Vci = volume (gal) of coating i (less water and exempt 

solvents) as applied that is being averaged during 

the 30-day period. 

Clwes = total volume (gal) of all coatings (less water and 

exempt solvents) as applied during each 30-day 

period for those coatings being averaged.

(5)(i) If the VOC content is found to be different when EPA 

Method 24 is used during an enforcement inspection from that 

used by the owner or operator in calculating Ga, recalculation of 

Ga is required using the new value. If more than one coating is 

involved, the recalculation shall be made once using all of the 

new values. 

(ii) If recalculation is required, an owner or operator may 

elect to include in the recalculation of Ga uncontrolled coatings 

that were not previously included provided appropriate and 
Page 91 of 174

sufficient records were maintained for these other coatings to 

allow daily recalculations. 

(iii) The recalculated value of Ga under either paragraph 

(f)(5)(i) or (f)(5)(ii) of this section shall be used to 

determine compliance. 

(g) Overall VOC and/or organic HAP control efficiency—

carbon adsorber. Each owner or operator subject to the 

requirements of §63.745(d), §63.746(c), or §63.747(d) shall 

demonstrate initial compliance with the requirements of this 

subpart by following the procedures of paragraph (g)(1), (2), 

(3), (4), or (5) as applicable and paragraphs (6), (7), and (8) 

of this section. When an initial compliance demonstration is 

required by this subpart, the procedures in paragraphs (g)(9) 

through (g)(14) of this section shall be used in determining 

initial compliance with the provisions of this subpart. 

(1) To demonstrate initial and continuous compliance with 

§63.745(d), §63.746(c), or §63.747(d) when emissions are 

controlled by a dedicated solvent recovery device, each owner or 

operator of the affected operation may perform a liquid-liquid 

HAP or VOC material balance over rolling 7- to 30-day periods in 

lieu of demonstrating compliance through the methods in 

paragraph (g)(2), (g)(3), or (g)(4) of this section. Results of 

the material balance calculations performed to demonstrate 

initial compliance shall be submitted to the Administrator with 
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the notification of compliance status required by §63.9(h) and 

by §63.753 (c)(1)(iv), (d)(3)(i), and (e)(3). When demonstrating 

compliance by this procedure, §63.7(e)(3) of subpart A does not 

apply. The amount of liquid HAP or VOC applied and recovered 

shall be determined as discussed in paragraph (g)(1)(iii) of 

this section. The overall HAP or VOC emission reduction (R) is 

calculated using equation 9: 

(i) The value of RSi is zero unless the owner or operator 

submits the following information to the Administrator for 

approval of a measured RSi value that is greater than zero: 

(A) Measurement techniques; and 

(B) Documentation that the measured value of RSi exceeds 

zero. 

(ii) The measurement techniques of paragraph (g)(1)(i)(A) 

of this section shall be submitted to the Administrator for 

approval with the notification of performance test required 

under §63.7(b). 

(iii) Each owner or operator demonstrating compliance by 

the test method described in paragraph (g)(1) of this section 

shall: 

(A) Measure the amount of coating or stripper as applied; 
Page 93 of 174

(B) Determine the VOC or HAP content of all coating and 

stripper applied using the test method specified in §63.750(c) 

(1) through (3) or (e) (1) and (2) of this section; 

(C) Install, calibrate, maintain, and operate, according to 

the manufacturer's specifications, a device that indicates the 

amount of HAP or VOC recovered by the solvent recovery device 

over rolling 7- to 30-day periods; the device shall be certified 

by the manufacturer to be accurate to within ±2.0 percent, and 

this certification shall be kept on record; 

(D) Measure the amount of HAP or VOC recovered; and 

(E) Calculate the overall HAP or VOC emission reduction (R) 

for rolling 7- to 30-day periods using equation 9. 

(F) Compliance is demonstrated if the value of R is equal 

to or greater than the overall HAP control efficiencies required 

by §63.745(d), §63.746(c), or §63.747(d). 

(2) To demonstrate initial compliance with §63.745(d), 

§63.746(c), or §63.747(d) when affected HAP emission points are 

controlled by an emission control device other than a fixed-bed 

carbon adsorption system with individual exhaust stacks for each 

carbon adsorber vessel, each owner or operator of an affected 

source shall perform a gaseous emission test using the following 

procedures. 

(i) Construct the overall HAP emission reduction system so 

that all volumetric flow rates and total HAP or VOC emissions 
Page 94 of 174

can be accurately determined by the applicable test methods and 

procedures specified in §63.750(g) (9) through (14). 

(ii) Determine capture efficiency from the HAP emission 

points by capturing, venting, and measuring all HAP emissions 

from the HAP emission points. During a performance test, the 

owner or operator of affected HAP emission points located in an 

area with other gaseous emission sources not affected by this 

subpart shall isolate the affected HAP emission points from all 

other gaseous emission points by one of the following methods: 

(A) Build a temporary total enclosure around the affected 

HAP emission point(s); or 

(B) Shut down all gaseous emission points not affected by 

this subpart and continue to exhaust fugitive emissions from the 

affected HAP emission points through any building ventilation 

system and other room exhausts such as drying ovens. All 

ventilation air must be vented through stacks suitable for 

testing. 

(iii) Operate the emission control device with all affected 

HAP emission points connected and operating. 

(iv) Determine the efficiency (E) of the control device 

using equation 10: 

(v) Determine the efficiency (F) of the capture system 

using equation 11: 
Page 95 of 174

(vi) For each HAP emission point subject to §63.745(d), 

§63.746(c), or §63.747(d), compliance is demonstrated if the 

product of (E) × (F) is equal to or greater than the overall HAP 

control efficiencies required under §63.745(d), §63.746(c), or 

§63.747(d).

(3) To demonstrate compliance with §63.745(d), §63.746(c), 

or §63.747(d) when affected HAP emission points are controlled 

by a fixed-bed carbon adsorption system with individual exhaust 

stacks for each carbon adsorber vessel, each owner or operator 

of an affected source shall perform a gaseous emission test 

using the following procedures: 

(i) Construct the overall HAP emission reduction system so 

that each volumetric flow rate and the total HAP emissions can 

be accurately determined by the applicable test methods and 

procedures specified in §63.750(g) (9) through (14); 

(ii) Assure that all HAP emissions from the affected HAP 

emission point(s) are segregated from gaseous emission points 
Page 96 of 174

not affected by this subpart and that the emissions can be 

captured for measurement, as described in paragraphs (g)(2)(ii) 

(A) and (B) of this section;

(iii) Operate the emission control device with all affected 

HAP emission points connected and operating; 

(iv) Determine the efficiency (Hv) of each individual carbon 

adsorber vessel (v) using equation 12: 

(v) Determine the efficiency of the carbon adsorption 

system (Hsys) by computing the average efficiency of the 

individual carbon adsorber vessels as weighted by the volumetric 

flow rate (Qhv) of each individual carbon adsorber vessel (v) 

using equation 13: 

(vi) Determine the efficiency (F) of the capture system 

using equation 11. 

(vii) For each HAP emission point subject to §63.745(d), 

§63.746(c), or §63.747(d), compliance is demonstrated if the 

product of (Hsys) × (F) is equal to or greater than the overall 
Page 97 of 174

HAP control efficiency required by §63.745(d), §63.746(c), or 

§63.747(d).

(4) An alternative method of demonstrating compliance with 

§63.745(d), §63.746(c), or §63.747(d) is the installation of a 

total enclosure around the affected HAP emission point(s) and 

the ventilation of all HAP emissions from the total enclosure to 

a control device with the efficiency specified in paragraph 

(g)(4)(iii) of this section. If this method is selected, the 

compliance test methods described in paragraphs (g)(1), (g)(2), 

and (g)(3) of this section are not required. Instead, each owner 

or operator of an affected source shall: 

(i) Demonstrate that a total enclosure is installed. An 

enclosure that meets the requirements in paragraphs (g)(4)(i) 

(A) through (D) of this section shall be considered a total 

enclosure. The owner or operator of an enclosure that does not 

meet these requirements may apply to the Administrator for 

approval of the enclosure as a total enclosure on a case-by-case 

basis. The enclosure shall be considered a total enclosure if it 

is demonstrated to the satisfaction of the Administrator that 

all HAP emissions from the affected HAP emission point(s) are 

contained and vented to the control device. The requirements for

automatic approval are as follows: 
Page 98 of 174

(A) The total area of all natural draft openings shall not 

exceed 5% of the total surface area of the total enclosure's 

walls, floor, and ceiling; 

(B) All sources of emissions within the enclosure shall be 

a minimum of four equivalent diameters away from each natural 

draft opening; 

(C) The average inward face velocity (FV) across all 

natural draft openings shall be a minimum of 3,600 meters per 

hour as determined by the following procedures: 

(1) All forced makeup air ducts and all exhaust ducts are 

constructed so that the volumetric flow rate in each can be 

accurately determined by the test methods and procedures 

specified in §63.750(g) (10) and (11); volumetric flow rates 

shall be calculated without the adjustment normally made for 

moisture content; and 

(2) Determine FV by equation 14: 

(D) The air passing through all natural draft openings 

shall flow into the enclosure continuously. If FV is less than 

or equal to 9,000 meters per hour, the continuous inward flow of 

air shall be verified by continuous observation using smoke 
Page 99 of 174

tubes, streamers, tracer gases, or other means approved by the 

Administrator over the period that the volumetric flow rate 

tests required to determine FV are carried out. If FV is greater 

than 9,000 meters per hour, the direction of airflow through the 

natural draft openings shall be presumed to be inward at all 

times without verification. 

(ii) Determine the control device efficiency using equation 

10 or equations 12 and 13, as applicable, and the test methods 

and procedures specified in §63.750(g) (9) through (14). 

(iii) Compliance shall be achieved if the installation of a 

total enclosure is demonstrated and the value of E determined 

from equation 10 (or the value of Hsys determined from equations 

12 and 13, as applicable) is equal to or greater than the 

overall HAP control efficiencies required under §63.745(d), 

§63.746(c), or §63.747(d). 

(5) When nonregenerative carbon adsorbers are used to 

comply with §63.745(d), §63.746(c), or §63.747(d), the owner or 

operator may conduct a design evaluation to demonstrate initial 

compliance in lieu of following the compliance test procedures 

of paragraphs (g)(1), (2), (3), and (4) of this section. The 

design evaluation shall consider the vent stream composition, 

component concentrations, flow rate, relative humidity, and 

temperature, and shall establish the design exhaust vent stream 

organic compound concentration level, capacity of the carbon 
Page 100 of 174

bed, type and working capacity of activated carbon used for the

carbon bed, and design carbon replacement interval based on the 

total carbon working capacity of the control device and the 

emission point operating schedule. 

(6)(i) To demonstrate initial compliance with §63.745(d), 

§63.746(c), or §63.747(d) when hard piping or ductwork is used 

to direct VOC and HAP emissions from a VOC and HAP source to the 

control device, each owner or operator shall demonstrate upon 

inspection that the criteria of paragraph (g)(6)(i)(A) and 

paragraph (g)(6)(i) (B) or (C) of this section VR/FD are met. 

(A) The equipment shall be vented to a control device. 

(B) The control device efficiency (E or Hsys, as applicable) 

determined using equation 10 or equations 12 and 13, 

respectively, and the test methods and procedures specified in 

§63.750(g) (9) through (14), shall be equal to or greater than 

the overall HAP control efficiency required by §63.745(d), 

§63.746(c), or §63.747(d). 

(C) When a nonregenerative carbon adsorber is used, the 

ductwork from the affected emission point(s) shall be vented to 

the control device and the carbon adsorber shall be 

demonstrated, through the procedures of §63.750(g) (1), (2), 

(3), (4), or (5), to meet the requirements of §63.745(d), 

§63.746(c), or §63.747(d). 
Page 101 of 174

(7) Startups and shutdowns are normal operation for this 

source category. Emissions from these activities are to be 

included when determining if the standards specified in 

§63.745(d), §63.746(c), or §63.747(d) are being attained. 

(8) An owner or operator who uses compliance techniques 

other than those specified in this subpart shall submit a 

description of those compliance procedures, subject to the 

Administrator's approval, in accordance with §63.7(f) of subpart 

A. 

(9) Either EPA Method 18 or EPA Method 25A of appendix A of 

part 60, as appropriate to the conditions at the site, shall be 

used to determine VOC and HAP concentration of air exhaust 

streams as required by §63.750(g) (1) through (6). The owner or 

operator shall submit notice of the intended test method to the 

Administrator for approval along with the notification of the 

performance test required under §63.7(b). Method selection shall 

be based on consideration of the diversity of organic species 

present and their total concentration and on consideration of 

the potential presence of interfering gases. Except as indicated 

in paragraphs (g)(9) (i) and (ii) of this section, the test 

shall consist of three separate runs, each lasting a minimum of 

30 minutes. 

(i) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 
Page 102 of 174

carbon adsorption system with a common exhaust stack for all the 

individual carbon adsorber vessels pursuant to paragraph (g) (2) 

or (4) of this section, the test shall consist of three separate 

runs, each coinciding with one or more complete sequences 

through the adsorption cycles of all of the individual carbon 

adsorber vessels.

(ii) When either EPA Method 18 or EPA Method 25A is to be 

used in the determination of the efficiency of a fixed-bed 

carbon adsorption system with individual exhaust stacks for each 

carbon adsorber vessel pursuant to §63.750(g) (3) or (4), each 

carbon adsorber vessel shall be tested individually. The test 

for each carbon adsorber vessel shall consist of three separate 

runs. Each run shall coincide with one or more complete 

adsorption cycles. 

(10) EPA Method 1 or 1A of appendix A of part 60 is used 

for sample and velocity traverses. 

(11) EPA Method 2, 2A, 2C, or 2D of appendix A of part 60 

is used for velocity and volumetric flow rates. 

(12) EPA Method 3 of appendix A of part 60 is used for gas 

analysis. 

(13) EPA Method 4 of appendix A of part 60 is used for 

stack gas moisture. 
Page 103 of 174

(14) EPA Methods 2, 2A, 2C, 2D, 3, and 4 shall be 

performed, as applicable, at least twice during each test 

period. 

(h) Overall VOC and/or organic HAP control efficiency—

control devices other than carbon adsorbers. Calculate the 

overall control efficiency of a control system with a control 

device other than a carbon adsorber using the following 

procedure. 

(1) Calculate the overall control efficiency using equation 

15: 

where: 

Ek = overall VOC and/or organic HAP control efficiency 

(expressed as a decimal) of control system k. 

Rk = destruction or removal efficiency (expressed as a 

decimal) of total organic compounds or total organic 

HAP for control device k as determined under 

paragraph (h)(2) of this section. 

Fk = capture efficiency (expressed as a decimal) of 

capture system k as determined under paragraph 

(h)(3) of this section.

(2) The organic HAP destruction or removal efficiency Rk of 

a control device other than a carbon adsorber shall be 

determined using the procedures described below. The destruction 

efficiency may be measured as either total organic HAP or as TOC 

minus methane and ethane according to these procedures. 
Page 104 of 174

(i) Use Method 1 or 1A of 40 CFR part 60, appendix A, as 

appropriate, to select the sampling sites. 

(ii) Determine the gas volumetric flow rate using Method 2, 

2A, 2C, or 2D of 40 CFR part 60, appendix A, as appropriate. 

(iii) Use Method 18 of 40 CFR part 60, appendix A, to 

measure either TOC minus methane and ethane or total organic 

HAP. Alternatively, any other method or data that have been 

validated according to the applicable procedures in Method 301 

of this part may be used. 

(iv) Use the following procedure to calculate the 

destruction or removal efficiency: 

(A) The destruction or removal efficiency test shall 

consist of three runs. The minimum sampling time for each run 

shall be 1 hour in which either an integrated sample or a 

minimum of four grab samples shall be taken. If grab sampling is 

used, the samples shall be taken at approximately equal 

intervals in time such as 15-minute intervals during the run. 

(B) Calculate the mass rate of either TOC (minus methane 

and ethane) or total organic HAP (Ei, Eo using equations 16 and 

17: 
Page 105 of 174

where: 

Ei, Eo = mass rate of TOC (minus methane and ethane) or total 

organic HAP at the inlet and outlet of the control 

device, respectively, dry basis, kg/hr. 

K2 = constant, 2.494×10−6 (parts per million)−1 (gram-mole 

per standard cubic meter) (kilogram/gram) 

(minute/hour), where standard temperature for (grammole per standard cubic meter) is 20 °C. 

n = number of sample components in the gas stream. 

Cij, Coj = concentration of sample component j of the gas 

stream at the inlet and outlet of the control 

device, respectively, dry basis, parts per 

million by volume. 

Mij, Moj = molecular weight of sample component j of the gas 

stream at the inlet and outlet of the control 

device, respectively, gram/gram-mole. 

Qi, Qo = flow rate of gas stream at the inlet and outlet 

of the control device, respectively, dry standard 

cubic meter per minute.

(1) Where the mass rate of TOC is being calculated, all 

organic compounds (minus methane and ethane) measured by EPA 

Method 18 shall be summed using equation 16 in paragraph 

(h)(2)(iv)(B) of this section. 

(2) Where the mass rate of total organic HAP is being 

calculated, only the organic HAP species shall be summed using 

equation 17 in paragraph (h)(2)(iv)(B) of this section. The list 

of organic HAP is provided in §63.104 of subpart F of this part. 

(C) Calculate the destruction or removal efficiency for TOC 

(minus methane and ethane) or total organic HAP using equation 

18:
Page 106 of 174

where:

R = destruction or removal efficiency of control device, 

percent. 

Ei = mass rate of TOC (minus methane and ethane) or total 

organic HAP at the inlet to the control device as 

calculated under paragraph (h)(2)(iv)(B) of this 

section, kg TOC per hour or kg organic HAP per hour. 

Eo = mass rate of TOC (minus methane and ethane) or total 

organic HAP at the outlet of the control device, as 

calculated under paragraph (h)(2)(iv)(B) of this 

section, kg TOC per hour or kg organic HAP per hour.

(3) Determine the capture efficiency Fk of each capture 

system to which organic HAP and VOC emissions from coating 

operations are vented. The capture efficiency value shall be 

determined using Procedure T—Criteria for and Verification of a 

Permanent or Temporary Total Enclosure as found in appendix B to 

§52.741 of part 52 of this chapter for total enclosures, and the 

capture efficiency protocol specified in §52.741(a)(4)(iii) of 

part 52 of this chapter for all other enclosures. 

(i)(1) Alternative application method—primers and,

topcoats, and specialty coatings. Each owner or operator seeking 

to use an alternative application method (as allowed in 

§63.745(f)(1)(ix)) in complying with the standards for primers

and, topcoats, and specialty coatings shall use the procedures 

specified in paragraphs (i)(2)(i) and (i)(2)(ii) or (i)(2)(iii) 

of this section to determine the organic HAP and VOC emission 
Page 107 of 174

levels of the alternative application technique as compared to 

either HVLP or electrostatic spray application methods.

(2)(i) For the process or processes for which the 

alternative application method is to be used, the total organic 

HAP and VOC emissions shall be determined for an initial 30-day 

period, the period of time required to apply coating to five 

completely assembled aircraft, or a time period approved by the 

permitting agency. During this initial period, only HVLP or 

electrostatic spray application methods shall be used. The 

emissions shall be determined based on the volumes, organic HAP 

contents (less water), and VOC contents (less water and exempt 

solvents) of the coatings as applied. 

(ii) Upon implementation of the alternative application 

method, use the alternative application method in production on 

actual production parts or assemblies for a period of time 

sufficient to coat an equivalent amount of parts and assemblies 

with coatings identical to those used in the initial 30-day 

period. The actual organic HAP and VOC emissions shall be 

calculated for this post-implementation period. 

(iii) Test the proposed application method against either 

HVLP or electrostatic spray application methods in a laboratory 

or pilot production area, using parts and coatings 

representative of the process(es) where the alternative method 

is to be used. The laboratory test will use the same part 
Page 108 of 174

configuration(s) and the same number of parts for both the 

proposed method and the HVLP or electrostatic spray application 

methods.

(iv) Whenever the approach in either paragraph (i)(2)(ii) 

or (i)(2)(iii) of this section is used, the owner or operator 

shall calculate both the organic HAP and VOC emission reduction 

using equation:

where:

P = organic HAP or VOC emission reduction, percent.

Eb = organic HAP or VOC emissions, in pounds, before the 

alternative application technique was implemented, 

as determined under paragraph (i)(2)(i) of this 

section.

Ea = organic HAP of VOC emissions, in pounds, after the 

alternative application technique was implemented, 

as determined under paragraph (i)(2)(ii) of this 

section.

(3) Each owner or operator seeking to demonstrate that an 

alternative application method achieves emission reductions 

equivalent to HVLP or electrostatic spray application methods 

shall comply with the following: 

(i) Each coating shall be applied such that the dried film 

thickness is within the range specified by the applicable 

specification(s) for the aerospace vehicle or component being 

coated. 
Page 109 of 174

(ii) If no such dried film thickness specification(s) 

exists, the owner or operator shall ensure that the dried film 

thickness applied during the initial 30-day period is equivalent 

to the dried film thickness applied during the alternative 

application method test period for similar aerospace vehicles or 

components. 

(iii) Failure to comply with these dried film thickness 

requirements shall invalidate the test results obtained under 

paragraph (i)(2)(i) of this section.

(j) Spot stripping and decal removal. Each owner or 

operator seeking to comply with §63.746(b)(3) shall determine 

the volume of organic HAP-containing chemical strippers or 

alternatively the weight of organic HAP used per aircraft using 

the procedure specified in paragraphs (j)(1) through (j)(3) of 

this section.

(1) For each chemical stripper used for spot stripping and 

decal removal, determine for each annual period the total volume 

as applied or the total weight of organic HAP using the 

procedure specified in paragraph (d)(2) of this section.

(2) Determine the total number of aircraft for which 

depainting operations began during the annual period as 

determined from company records. 

(3) Calculate the annual average volume of organic HAPcontaining chemical stripper or weight of organic HAP used for 
Page 110 of 174

spot stripping and decal removal per aircraft using equation 20 

(volume) or equation 21 (weight):

where:

C = annual average volume (gal per aircraft) of organic 

HAP-containing chemical stripper used for spot 

stripping and decal removal.

n = number of organic HAP-containing chemical strippers 

used in the annual period.

Vsi = volume (gal) of organic HAP-containing chemical 

stripper (i) used during the annual period.

A = number of aircraft for which depainting operations 

began during the annual period.

where:

C = annual average weight (lb per aircraft) of organic 

HAP (chemical stripper) used for spot stripping and 

decal removal.

m = number of organic HAP contained in each chemical 

stripper, as applied.

n = number of organic HAP-containing chemical strippers 

used in the annual period.

Whi = weight fraction (expressed as a decimal) of each

organic HAP (i) contained in the chemical stripper, 

as applied, for each aircraft depainted.

Dhi = density (lb/gal) of each organic HAP-containing 

chemical stripper (i), used in the annual period.
Page 111 of 174

Vsi = volume (gal) of organic HAP-containing chemical 

stripper (i) used during the annual period.

A = number of aircraft for which depainting operations 

began during the annual period.

(k) Organic HAP content level determination—compliant 

chemical milling maskants. For those uncontrolled chemical 

milling maskants complying with the chemical milling maskant 

organic HAP content limit specified in § 63.747(c)(1) without 

being averaged, the following procedures in paragraph (k)(1) of 

this section shall be used to determine the mass of organic HAP 

emitted per unit volume of coating (chemical milling maskant) i 

as applied (less water), Hi (lb/gal). As an alternative to the 

procedures in paragraph (k)(1) of this section, an owner or 

operator may use coating manufacturer’s supplied data to 

demonstrate that organic HAP emitted per volume of coating (less 

water), as applied, is less than or equal to the applicable 

organic HAP limit specified in § 63.747(c).

(1) For coatings that contain no exempt solvents, determine 

the total organic HAP content using manufacturer's supplied data 

or Method 24 of 40 CFR part 60, appendix A to determine the VOC 

content. The VOC content shall be used as a surrogate for total 

HAP content for coatings that contain no exempt solvent. If 

there is a discrepancy between the manufacturer's formulation 

data and the results of the Method 24 analysis, compliance shall 

be based on the results from the Method 24 analysis.
Page 112 of 174

When Method 24 is used to determine the VOC content of 

water-reducible coatings, the precision adjustment factors in 

Reference Method 24 shall be used. If the adjusted analytical 

VOC content is less than the formulation solvent content, then 

the analytical VOC content should be set equal to the 

formulation solvent content. 

(2) [Reserved]

(l) Organic HAP content level determination—averaged 

chemical milling maskants. For those uncontrolled chemical 

milling maskants that are averaged together in order to comply 

with the chemical milling maskant organic HAP content level 

specified in §63.747(c)(1), the procedure specified in 

paragraphs (l)(1) through (l)(4) of this section shall be used 

to determine the monthly volume-weighted average mass of organic 

HAP emitted per volume of chemical milling maskant (less water) 

as applied, unless the permitting agency specifies a shorter 

averaging period as part of an ambient ozone control program. 

(1) Determine the total organic HAP weight fraction as 

applied of each chemical milling maskant used during each 30-day 

period using the procedure specified in paragraph (d)(1) of this 

section. 

(2) Determine for each 30-day period: 
Page 113 of 174

(i) The individual volume of each chemical milling maskant 

applied in terms of total gallons (less water) (using the 

procedure specified in paragraph (d)(2) of this section), and 

(ii) The total volume in gallons of all chemical milling 

maskants (less water) as applied by summing the individual 

volumes of each chemical milling maskant as applied (less 

water). 

(3) Determine the density of each chemical milling maskant 

as applied used during each 30-day period using the procedure 

specified in paragraph (d)(3) of this section. 

(4) Calculate the volume-weighted average mass of organic 

HAP emitted per unit volume (lb/gal) of chemical milling maskant 

(less water) as applied for all chemical milling maskants during 

each 30-day period using equation 22:

where:

Ha = volume-weighted mass of organic HAP emitted per unit 

volume of chemical milling maskants (lb/gal) (less 

water) as applied during each 30-day period for 

those chemical milling maskants being averaged. 

n = number of chemical milling maskants being averaged.

WHi = weight fraction (expressed as a decimal) of organic 

HAP in chemical milling maskant i (less water) as 

applied during each 30-day period that is averaged. 
Page 114 of 174

Dmi = density (lb chemical milling maskant per gal 

coating) of chemical milling maskant i as applied 

during each 30-day period that is averaged. 

Vmi = volume (gal) of chemical milling maskant i (less 

water) as applied during the 30-day period that is 

averaged. 

Mlw = total volume (gal) of all chemical milling maskants 

(less water) as applied during each 30-day period 

that is averaged.

(m) VOC content level determination—compliant chemical 

milling maskants. For those uncontrolled chemical milling 

maskants complying with the chemical milling maskant VOC content 

limit specified in § 63.747(c)(2) without being averaged, the 

procedure specified in paragraphs (m)(1) and (m)(2) of this 

section shall be used to determine the mass of VOC emitted per 

volume of chemical milling maskant (less water and exempt 

solvents) as applied. As an alternative to the procedures in 

paragraphs (m)(1) and (2) of this section, an owner or operator 

may use coating manufacturer’s supplied data to demonstrate that 

VOC emitted per volume of coating (less water and exempt 

solvents), as applied, is less than or equal to the applicable 

VOC limit specified in § 63.747(c).

(1) Determine the mass of VOC emitted per unit volume of 

chemical milling maskant (lb/gal) (less water and exempt 

solvents) as applied, Gi, for each chemical milling maskant using 

the procedures specified in paragraphs (e)(1) and (e)(2) of this 

section. 
Page 115 of 174

(2)(i) If the VOC content is found to be different when EPA 

Method 24 is used during an enforcement inspection from that 

used by the owner or operator in calculating Gi, compliance shall 

be based, except as provided in paragraph (m)(2)(ii) of this 

section, upon the VOC content obtained using EPA Method 24. 

(ii) If the VOC content of a chemical milling maskant 

obtained using EPA Method 24 would indicate noncompliance as 

determined under §63.749(h)(3)(i), an owner or operator may 

elect to average the chemical milling maskant with other 

uncontrolled chemical milling maskants and (re)calculate Ga

(using the procedure specified in paragraph (n) of this 

section), provided appropriate and sufficient records were 

maintained for all chemical milling maskants included in the 

average recalculation. The (re)calculated value of Ga for the 

averaged chemical milling maskants shall then be used to 

determine compliance. 

(n) VOC content level determination—averaged chemical 

milling maskants. For those uncontrolled chemical milling 

maskants that are averaged together in order to comply with the 

chemical milling maskant VOC content limit specified in 

§63.747(c)(2), the procedure specified in paragraphs (n)(1) 

through (n)(4) of this section shall be used to determine the 

monthly volume-weighted average mass of VOC emitted per volume 

of chemical milling maskant (less water and exempt solvents) as 
Page 116 of 174

applied, unless the permitting agency specifies a shorter 

averaging period as part of an ambient ozone control program. 

(1) Determine the VOC content of each chemical milling 

maskant (less water and exempt solvents) as applied used during 

each 30-day period using the procedure specified in paragraph 

(f)(1) of this section. 

(2)(i) Determine the individual volume of each chemical 

milling maskant applied in terms of total gallons (less water 

and exempt solvents) using the procedure specified in paragraph 

(f)(2) of this section, and 

(ii) Calculate the total volume in gallons of all chemical 

milling maskants (less water and exempt solvents) as applied by 

summing the individual volumes of each chemical milling maskant 

(less water and exempt solvents) as applied. 

(3) Calculate the volume-weighted average mass of VOC 

emitted per unit volume (lb/gal) of chemical milling maskant 

(less water and exempt solvents) as applied during each 30-day 

period using equation 23:

where: 

Ga = volume-weighted average mass of VOC per unit volume 

of chemical milling maskant (lb/gal) (less water 

and exempt solvents) as applied during each 30-day 
Page 117 of 174

period for those chemical milling maskants that are 

averaged. 

n = number of chemical milling maskants being averaged. 

(VOC)mi = VOC content (lb/gal) of chemical milling maskant i 

(less water and exempt solvents) as applied during 

the 30-day period that is averaged. 

Vmi = volume (gal) of chemical milling maskant i (less 

water and exempt solvents) as applied during the 

30-day period that is averaged. 

Mlwes = total volume (gal) of all chemical milling maskants 

(less water and exempt solvents) as applied during 

each 30-day period that is averaged.

(4)(i) If the VOC content is found to be different when EPA 

Method 24 is used during an enforcement inspection from that 

used by the owner or operator in calculating Ga, recalculation of 

Ga is required using the new value. If more than one chemical 

milling maskant is involved, the recalculation shall be made 

once using all of the new values. 

(ii) If recalculation is required, an owner or operator may 

elect to include in the recalculation of Ga uncontrolled chemical 

milling maskants that were not previously included provided 

appropriate and sufficient records were maintained for these 

other chemical milling maskants to allow daily recalculations. 

(iii) The recalculated value of Ga under either paragraph 

(n)(4)(i) or (n)(4)(ii) of this section shall be used to 

determine compliance. 

(o) Inorganic HAP emissions—dry particulate filter 

certification requirements. Dry particulate filters used to 
Page 118 of 174

comply with §§ 63.745(g)(2) or §63.746(b)(4) must be certified 

by the filter manufacturer or distributor, paint/depainting 

booth supplier, and/or the facility owner or operator using 

method 319 in appendix A of this part, to meet or exceed the 

efficiency data points found in Tables 12 and 23, or 34 and 45

of § 63.745 for existing or new sources respectively.

§ 63.751 Monitoring requirements.

(a) Enclosed spray gun cleaners. Each owner or operator 

using an enclosed spray gun cleaner under §63.744(c)(1) shall 

visually inspect the seals and all other potential sources of 

leaks associated with each enclosed gun spray cleaner system at 

least once per month. Each inspection shall occur while the 

system is in operation. 

(b) Incinerators and carbon adsorbers—initial compliance 

demonstrations. Each owner or operator subject to the 

requirements in this subpart must demonstrate initial compliance 

with the requirements of §§63.745(d), 63.746(c), and 63.747(d) 

of this subpart. Each owner or operator using a carbon adsorber 

to comply with the requirements in this subpart shall comply 

with the requirements specified in paragraphs (b)(1) through (7) 

of this section. Each owner or operator using an incinerator to 

comply with the requirements in this subpart shall comply with 

the requirements specified in paragraphs (b)(8) through (12) of 

this section. 
Page 119 of 174

(1) Except as allowed by paragraph (b)(2) or (b)(5) of this 

section, for each control device used to control organic HAP or 

VOC emissions, the owner or operator shall fulfill the 

requirements of paragraph (b)(1) (i) or (ii) of this section. 

(i) The owner or operator shall establish as a sitespecific operating parameter the outlet total HAP or VOC 

concentration that demonstrates compliance with §63.745(d), 

§63.746(c), or §63.747(d) as appropriate; or 

(ii) The owner or operator shall establish as the sitespecific operating parameter the control device efficiency that 

demonstrates compliance with §63.745(d), §63.746(c), or 

§63.747(d). 

(iii) When a nonregenerative carbon adsorber is used to 

comply with §63.745(d), §63.746(c), or §63.747(d), the sitespecific operating parameter value may be established as part of 

the design evaluation used to demonstrate initial compliance. 

Otherwise, the site-specific operating parameter value shall be 

established during the initial performance test conducted 

according to the procedures of §63.750(g). 

(2) For each nonregenerative carbon adsorber, in lieu of 

meeting the requirements of §63.751(b)(1), the owner or operator 

may establish as the site-specific operating parameter the 

carbon replacement time interval, as determined by the maximum 

design flow rate and organic concentration in the gas stream 
Page 120 of 174

vented to the carbon adsorption system. The carbon replacement 

time interval shall be established either as part of the design 

evaluation to demonstrate initial compliance or during the 

initial performance test conducted according to the procedures 

in §63.750(g) (1), (2), (3), or (4). 

(3) Each owner or operator venting solvent HAP emissions 

from a source through a room, enclosure, or hood, to a control 

device to comply with §63.745(d), §63.746(c), or §63.747(d) 

shall: 

(i) Submit to the Administrator with the compliance status 

report required by §63.9(h) of the General Provisions a plan 

that: 

(A) Identifies the operating parameter to be monitored to 

ensure that the capture efficiency measured during the initial 

compliance test is maintained; 

(B) Discusses why this parameter is appropriate for 

demonstrating ongoing compliance; and 

(C) Identifies the specific monitoring procedures; 

(ii) Set the operating parameter value, or range of values, 

that demonstrate compliance with §63.745(d), §63.746(c), or 

§63.747(d), as appropriate; and 

(iii) Conduct monitoring in accordance with the plan 

submitted to the Administrator unless comments received from the 

Administrator require an alternate monitoring scheme. 
Page 121 of 174

(4) Owners or operators subject to §63.751(b) (1), (2), or 

(3) shall calculate the site-specific operating parameter value, 

or range of values, as the arithmetic average of the maximum 

and/or minimum operating parameter values, as appropriate, that 

demonstrate compliance with §63.745(d), §63.746(c), or 

§63.747(d) during the multiple test runs required by §63.750 

(g)(2) and (g)(1). 

(5) For each solvent recovery device used to comply with 

§63.745(d), §63.746(c), or §63.747(d), in lieu of meeting the 

requirements of paragraph (b)(1) of this section, the results of 

the material balance calculation conducted in accordance with 

§63.750(g)(1) may serve as the site-specific operating parameter 

that demonstrates compliance with §63.745(d), §63.746(c), or 

§63.747(d). 

(6) Continuous compliance monitoring. Following the date on 

which the initial compliance demonstration is completed, 

continuous compliance with §63.745(d), §63.746(c), or §63.747(d) 

of this subpart shall be demonstrated as outlined in this 

paragraph. 

(i) Each owner or operator of an affected source subject to 

§63.745(d), §63.746(c), or §63.747(d) of this subpart shall 

monitor the applicable parameters specified in paragraph 

(b)(6)(ii), (b)(6)(iii), or (b)(6)(iv) of this section depending 

on the type of control technique used. 
Page 122 of 174

(ii) Compliance monitoring shall be subject to the 

following provisions: 

(A) Except as allowed by paragraph (b)(6)(iii)(A)(2) of 

this section, all continuous emission monitors shall comply with 

performance specification (PS) 8 or 9 in 40 CFR part 60, 

appendix B, as appropriate depending on whether VOC or HAP 

concentration is being measured. The requirements in appendix F 

of 40 CFR part 60 shall also be followed. In conducting the 

quarterly audits required by appendix F, owners or operators 

shall challenge the monitors with compounds representative of 

the gaseous emission stream being controlled. 

(B) If the effluent from multiple emission points are 

combined prior to being channeled to a common control device, 

the owner or operator is required only to monitor the common 

control device, not each emission point. 

(iii) Owners or operators complying with §63.745(d), 

§63.746(c), or §63.747(d) through the use of a control device 

and establishing a site-specific operating parameter in 

accordance with paragraph (b)(1) of this section shall fulfill 

the requirements of paragraph (b)(6)(iii)(A) of this section and 

paragraph (b)(6)(iii)(B) or (C) of this section, as appropriate.

(A) The owner or operator shall install, calibrate, 

operate, and maintain a continuous emission monitor. 
Page 123 of 174

(1) The continuous emission monitor shall be used to 

measure continuously the total HAP or VOC concentration at both 

the inlet and the outlet whenever HAP from coating and paint 

stripping operations are vented to the control device, or when 

continuous compliance is demonstrated through a percent 

efficiency calculation; or 

(2) For owners or operators using a nonregenerative carbon 

adsorber, in lieu of using continuous emission monitors as 

specified in paragraph (b)(6)(iii)(A)(1) of this section, the 

owner or operator may use a portable monitoring device to 

monitor total HAP or VOC concentration at the inlet and outlet 

or the outlet of the carbon adsorber as appropriate. 

(a) The monitoring device shall be calibrated, operated, 

and maintained in accordance with the manufacturer's 

specifications. 

(b) The monitoring device shall meet the requirements of 

part 60, appendix A, Method 21, sections 2, 3, 4.1, 4.2, and 

4.4. The calibration gas shall either be representative of the 

compounds to be measured or shall be methane, and shall be at a 

concentration associated with 125% of the expected organic 

compound concentration level for the carbon adsorber outlet 

vent. 

(c) The probe inlet of the monitoring device shall be 

placed at approximately the center of the carbon adsorber outlet 
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vent. The probe shall be held there for at least 5 minutes 

during which flow into the carbon adsorber is expected to occur. 

The maximum reading during that period shall be used as the 

measurement. 

(B) If complying with §63.745(d), §63.746(c), or §63.747(d) 

through the use of a carbon adsorption system with a common 

exhaust stack for all of the carbon vessels, the owner or 

operator shall not operate the control device at an average 

control efficiency less than that required by §63.745(d), 

§63.746(c), or §63.747(d) for three consecutive adsorption 

cycles. 

(C) If complying with §63.745(d), §63.746(c), or §63.747(d) 

through the use of a carbon adsorption system with individual 

exhaust stacks for each of the multiple carbon adsorber vessels, 

the owner or operator shall not operate any carbon adsorber 

vessel at an average control efficiency less than that required 

by §63.745(d), §63.746(c), or §63.747(d) as calculated daily 

using a 7 to 30-day rolling average. 

(D) If complying with §63.745(d), §63.746(c), or §63.747(d) 

through the use of a nonregenerative carbon adsorber, in lieu of 

the requirements of paragraph (b)(6)(iii) (B) or (C) of this 

section, the owner or operator may monitor the VOC or HAP 

concentration of the adsorber exhaust daily, at intervals no 

greater than 20 percent of the design carbon replacement 
Page 125 of 174

interval, whichever is greater, or at a frequency as determined 

by the owner or operator and approved by the Administrator.

(iv) Owners or operators complying with §63.745(d), 

§63.746(c), or §63.747(d) through the use of a nonregenerative 

carbon adsorber and establishing a site-specific operating 

parameter for the carbon replacement time interval in accordance 

with paragraph (b)(2) shall replace the carbon in the carbon 

adsorber system with fresh carbon at the predetermined time 

interval as determined in the design evaluation.

(v) Owners or operators complying with §63.745(d), 

§63.746(c), or §63.747(d) by capturing emissions through a room, 

enclosure, or hood shall install, calibrate, operate, and 

maintain the instrumentation necessary to measure continuously 

the site-specific operating parameter established in accordance 

with paragraph (b)(3) of this section whenever VOC and HAP from 

coating and stripper operations are vented through the capture 

device. The capture device shall not be operated at an average 

value greater than or less than (as appropriate) the operating 

parameter value established in accordance with paragraph (b)(3) 

of this section for any 3-hour period. 

(7) Owners or operators complying with paragraph (b)(4) or 

(b)(5) of this section shall calculate the site-specific 

operating parameter value as the arithmetic average of the 

minimum operating parameter values that demonstrate compliance 
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with §63.745(d)and §63.747(d) during the three test runs 

required by §63.750(h)(2)(iv). 

(8) All temperature monitoring equipment shall be 

installed, calibrated, maintained, and operated according to 

manufacturer's specifications. Every 3 months, facilities shall 

replace the temperature sensors or have the temperature sensors 

recalibrated. As an alternative, a facility may use a continuous 

emission monitoring system (CEMS) to verify that there has been 

no change in the destruction efficiency and effluent composition 

of the incinerator.

(9) Where an incinerator other than a catalytic incinerator 

is used, a thermocouple equipped with a continuous recorder 

shall be installed and continuously operated in the firebox or 

in the ductwork immediately downstream of the firebox in a 

position before any substantial heat exchange occurs. 

(10) Where a catalytic incinerator is used, thermocouples, 

each equipped with a continuous recorder, shall be installed and 

continuously operated in the gas stream immediately before and 

after the catalyst bed. 

(11) For each incinerator other than a catalytic 

incinerator, each owner or operator shall establish during each 

performance test during which compliance is demonstrated, 

including the initial performance test, the minimum combustion 

temperature as a site-specific operating parameter. This minimum 
Page 127 of 174

combustion temperature shall be the operating parameter value 

that demonstrates compliance with §63.745(d) and §63.747(d). 

(12) For each catalytic incinerator, each owner or operator 

shall establish during each performance test during which 

compliance is demonstrated, including the initial performance 

test, the minimum gas temperature upstream of the catalyst bed 

and the minimum gas temperature difference across the catalyst 

bed as site-specific operating parameters. These minimum 

temperatures shall be the operating parameter values that 

demonstrate compliance with §63.745(d) and §63.747(d). 

(c) Dry particulate filter, HEPA filter, and waterwash 

systems—primer and, topcoat, and specialty coating application 

operations. (1) Each owner or operator using a dry particulate 

filter system to meet the requirements of § 63.745(g)(2) shall, 

while primer or, topcoat, and specialty coating application 

operations are occurring, continuously monitor the pressure drop 

across the system and read and record the pressure drop once per 

shift following the recordkeeping requirements of § 63.752(d).

(2) Each owner or operator using a conventional waterwash 

system to meet the requirements of § 63.745(g)(2) shall, while 

primer or topcoat application operations are occurring, 

continuously monitor the water flow rate through the system and 

read and record the water flow rate once per shift following the 

recordkeeping requirements of § 63.752(d). Each owner or 
Page 128 of 174

operator using a pumpless waterwash system to meet the 

requirements of § 63.745(g)(2) shall, while primer and, topcoat, 

and specialty coating application operations are occurring, 

measure and record the parameter(s) recommended by the booth 

manufacturer that indicate booth performance once per shift, 

following the recordkeeping requirements of § 63.752(d).

(d) Particulate filters and waterwash booths—depainting 

operations. Each owner or operator using a dry particulate 

filter or a conventional waterwash system in accordance with the 

requirements of §63.746(b)(4) shall, while depainting operations 

are occurring, continuously monitor the pressure drop across the 

particulate filters or the water flow rate through the 

conventional waterwash system and read and record the pressure 

drop or the water flow rate once per shift following the 

recordkeeping requirements of §63.752(e). Each owner or operator 

using a pumpless waterwash system to meet the requirements of 

§63.746(b)(4) shall, while depainting operations are occurring, 

measure and record the parameter(s) recommended by the booth 

manufacturer that indicate booth performance once per shift, 

following the recordkeeping requirements of §63.752(e).

(e) Use of an alternative monitoring method—(1) General.

Until permission to use an alternative monitoring method has 

been granted by the Administrator under this paragraph, the 
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owner or operator of an affected source shall remain subject to 

the requirements of this section. 

(2) After receipt and consideration of written application, 

the Administrator may approve alternatives to any monitoring 

methods or procedures of this section including, but not limited 

to, the following: 

(i) Alternative monitoring requirements when the affected 

source is infrequently operated; or 

(ii) Alternative locations for installing continuous 

monitoring systems when the owner or operator can demonstrate 

that installation at alternate locations will enable accurate 

and representative measurements; or 

(iii) Alternatives to the American Society for Testing and 

Materials (ASTM) test methods or sampling procedures specified 

in this section. 

(3) If the Administrator finds reasonable grounds to 

dispute the results obtained by an alternative monitoring 

method, requirement, or procedure, the Administrator may require 

the use of a method, requirement, or procedure specified in this 

section. If the results of the specified and the alternative 

method, requirement, or procedure do not agree, the results 

obtained by the specified method, requirement, or procedure 

shall prevail. 
Page 130 of 174

(4)(i) Request to use alternative monitoring method. An 

owner or operator who wishes to use an alternative monitoring 

method shall submit an application to the Administrator as 

described in paragraph (e)(4)(ii) of this section. The 

application may be submitted at any time provided that the 

monitoring method is not used to demonstrate compliance with a 

relevant standard or other requirement. If the alternative 

monitoring method is to be used to demonstrate compliance with a 

relevant standard, the application shall be submitted not later 

than with the site-specific test plan required in §63.7(c) (if 

requested) or with the site-specific performance evaluation plan 

(if requested), or at least 60 days before the performance 

evaluation is scheduled to begin. 

(ii) The application shall contain a description of the 

proposed alternative monitoring system and information 

justifying the owner's or operator's request for an alternative 

monitoring method, such as the technical or economic 

infeasibility, or the impracticality, of the affected source 

using the required method. 

(iii) The owner or operator may submit the information 

required in this paragraph well in advance of the submittal 

dates specified in paragraph (e)(4)(i) of this section to ensure 

a timely review by the Administrator in order to meet the 

compliance demonstration date specified in this subpart. 
Page 131 of 174

(5) Approval of request to use alternative monitoring 

method. (i) The Administrator will notify the owner or operator 

of his/her intention to deny approval of the request to use an 

alternative monitoring method within 60 calendar days after 

receipt of the original request and within 60 calendar days 

after receipt of any supplementary information that is 

submitted. If notification of intent to deny approval is not 

received within 60 calendar days, the alternative monitoring 

method is to be considered approved. Before disapproving any 

request to use an alternative monitoring method, the 

Administrator will notify the applicant of the Administrator's 

intent to disapprove the request together with: 

(A) Notice of the information and findings on which the 

intended disapproval is based; and 

(B) Notice of opportunity for the owner or operator to 

present additional information to the Administrator before final 

action on the request. At the time the Administrator notifies 

the applicant of his or her intention to disapprove the request, 

the Administrator will specify how much time the owner or 

operator will have after being notified of the intended 

disapproval to submit the additional information. 

(ii) If the Administrator approves the use of an 

alternative monitoring method for an affected source under 

paragraph (e)(5)(i) of this section, the owner or operator of 
Page 132 of 174

such source shall continue to use the alternative monitoring 

method until approval is received from the Administrator to use 

another monitoring method as allowed by paragraph (e) of this 

section. 

(f) Reduction of monitoring data. (1) The data may be 

recorded in reduced or nonreduced form (e.g., parts per million 

(ppm) pollutant and % O2 or nanograms per Joule (ng/J) of 

pollutant). 

(2) All emission data shall be converted into units 

specified in this subpart for reporting purposes. After 

conversion into units specified in this subpart, the data may be 

rounded to the same number of significant digits as used in this 

subpart to specify the emission limit (e.g., rounded to the 

nearest 1% overall reduction efficiency). 

§ 63.752 Recordkeeping requirements.

(a) General. Each owner or operator of a source subject to 

this subpart shall fulfill all recordkeeping requirements 

specified in §63.10 (a), (b), (d), and (f). 63.10 (a), (b),

(d), and (f), except § 63.10(b)(2)(i), (iv) and (v). Each owner 

or operator must also record and maintain according to § 

63.10(b)(1) the information specified in paragraph (a)(1) 

through (a)(3) of this section.
Page 133 of 174

(1) In the event that an affected unit fails to meet an 

applicable standard, record the number of failures. For each 

failure record the date, time and duration of each failure.

(2) For each failure to meet an applicable standard, record 

and retain a list of the affected sources or equipment, an 

estimate of the quantity of each regulated pollutant emitted 

over any emission limit and a description of the method used to 

estimate the emissions. 

(3) Record actions taken to minimize emissions in 

accordance with § 63.743(e), and any corrective actions taken to 

return the affected unit to its normal or usual manner of 

operation.

(b) Cleaning operation. Each owner or operator of a new or 

existing cleaning operation subject to this subpart shall record 

the information specified in paragraphs (b)(1) through (b)(5) of 

this section, as appropriate. 

(1) The name, vapor pressure, and documentation showing the 

organic HAP constituents of each cleaning solvent used for 

affected cleaning operations at the facility.

(2) For each cleaning solvent used in hand-wipe cleaning 

operations that complies with the composition requirements 

specified in §63.744(b)(1) or for semi-aqueous cleaning solvents 

used for flush cleaning operations: 

(i) The name of each cleaning solvent used; 
Page 134 of 174

(ii) All data and calculations that demonstrate that the 

cleaning solvent complies with one of the composition 

requirements; and 

(iii) Annual records of the volume of each solvent used, as 

determined from facility purchase records or usage records. 

(3) For each cleaning solvent used in hand-wipe cleaning 

operations that does not comply with the composition 

requirements in §63.744(b)(1), but does comply with the vapor 

pressure requirement in §63.744(b)(2):

(i) The name of each cleaning solvent used; 

(ii) The composite vapor pressure of each cleaning solvent 

used; 

(iii) All vapor pressure test results, if appropriate, 

data, and calculations used to determine the composite vapor 

pressure of each cleaning solvent; and 

(iv) The amount (in gallons) of each cleaning solvent used 

each month at each operation. 

(4) For each cleaning solvent used for the exempt hand-wipe 

cleaning operations specified in §63.744(e) that does not 

conform to the vapor pressure or composition requirements of 

§63.744(b): 

(i) The identity and amount (in gallons) of each cleaning 

solvent used each month at each operation; and 
Page 135 of 174

(ii) A list of the processes set forth in §63.744(e) to 

which the cleaning operation applies. 

(5) A record of all leaks from enclosed spray gun cleaners 

identified pursuant to §63.751(a) that includes for each leak 

found: 

(i) Source identification; 

(ii) Date leak was discovered; and 

(iii) Date leak was repaired. 

(c) Primer and, topcoat, and specialty coating application 

operations—organic HAP and VOC. Each owner or operator required 

to comply with the organic HAP and VOC content limits specified 

in § 63.745(c) shall record the information specified in 

paragraphs (c)(1) through (c)(6) of this section, as 

appropriate. Each owner and operator using coating 

manufacturer’s supplied data to demonstrate compliance with the 

applicable organic HAP or VOC limit specified in § 63.745(c) may 

retain the manufacturer’s documentation and annual purchase 

records in place of the records specified in paragraphs (c)(2) 

and (c)(3) of this section. 

(1) The name and VOC content as received and as applied of 

each primer and, topcoat, and specialty coating used at the 

facility. 
Page 136 of 174

(2) For uncontrolled primers and, topcoats, and specialty 

coatings that meet the organic HAP and VOC content limits in 

§63.745(c)(1) through (c)(46) without averaging:

(i) The mass of organic HAP emitted per unit volume of 

coating as applied (less water) (Hi) and the mass of VOC emitted 

per unit volume of coating as applied (less water and exempt 

solvents) (Gi) for each coating formulation within each coating 

category used each month (as calculated using the procedures 

specified in §63.750(c) and (e));

(ii) All data, calculations, and test results (including 

EPA Method 24 results) used in determining the values of Hi and 

Gi; and 

(iii) The volume (gal) of each coating formulation within 

each coating category used each month.

(3) For “low HAP content” uncontrolled primers with organic 

HAP content less than or equal to 250 g/l (2.1 lb/gal) less 

water as applied and VOC content less than or equal to 250 g/l 

(2.1 lb/gal) less water and exempt solvents as applied: 

(i) Annual purchase records of the total volume of each 

primer purchased; and 

(ii) All data, calculations, and test results (including 

EPA Method 24 results) used in determining the organic HAP and 

VOC content as applied. These records shall consist of the 

manufacturer's certification when the primer is applied as 
Page 137 of 174

received, or the data and calculations used to determine Hi if 

not applied as received. 

(4) For primers and, topcoats, and specialty coatings

complying with the organic HAP or VOC content level by 

averaging: 

(i) The monthly volume-weighted average masses of organic 

HAP emitted per unit volume of coating as applied (less water) 

(Ha) and of VOC emitted per unit volume of coating as applied 

(less water and exempt solvents) (Ga) for all coatings (as 

determined by the procedures specified in §63.750(d) and (f)); 

and 

(ii) All data, calculations, and test results (including 

EPA Method 24 results) used to determine the values of Ha and Ga. 

(5) For primers and, topcoats, and specialty coatings that 

are controlled by a control device other than a carbon adsorber: 

(i) The overall control efficiency of the control system 

(as determined using the procedures specified in §63.750(h)) and 

all test results, data, and calculations used in determining the 

overall control efficiency; 

(ii) If an incinerator other than a catalytic incinerator 

is used, continuous records of the firebox temperature recorded 

under §63.751(b)(9) and all calculated 3-hour averages of the 

firebox temperature; and 
Page 138 of 174

(iii) If a catalytic incinerator is used, continuous 

records of the temperature recorded under §63.751(b)(10) and all 

calculated 3-hour averages of the recorded temperatures. 

(6) For primer andprimers, topcoats, and specialty coatings

that are controlled by a carbon adsorber: 

(i) The overall control efficiency of the control system 

(as determined using the procedures specified in §63.750(g)) and 

all test results, data, and calculations used in determining the 

overall control efficiency. The length of the rolling material 

balance period and all data and calculations used for 

determining this rolling period. The record of the certification 

of the accuracy of the device that measures the amount of HAP or 

VOC recovered; or 

(ii) For nonregenerative carbon adsorbers, the overall 

control efficiency of the control system (as determined using 

the procedures specified in §63.750(g)) and all test results, 

data, and calculations used in determining the overall control 

efficiency. The record of the carbon replacement time 

established as the site-specific operating parameter to 

demonstrate compliance. 

(d) Primer and, topcoat, and specialty coating application 

operations—inorganic HAP emissions. (1) Each owner or operator 

complying with § 63.745(g) for the control of inorganic HAP 

emissions from primer and, topcoat, and specialty coating
Page 139 of 174

application operations through the use of a dry particulate 

filter system or a HEPA filter system shall record the pressure 

drop across the operating system once each shift during which 

coating operations occur. 

(2) Each owner or operator complying with §63.745(g) 

through the use of a conventional waterwash system shall record 

the water flow rate through the operating system once each shift 

during which coating operations occur. Each owner or operator 

complying with §63.745(g) through the use of a pumpless 

waterwash system shall record the parameter(s) recommended by 

the booth manufacturer that indicate the performance of the 

booth once each shift during which coating operations occur.

(3) This log shall include the acceptable limit(s) of 

pressure drop, water flow rate, or for the pumpless waterwash 

booth, the booth manufacturer recommended parameter(s) that 

indicate the booth performance, as applicable, as specified by 

the filter or booth manufacturer or in locally prepared 

operating procedures.

(e) Depainting operations. Each owner or operator subject 

to the depainting standards specified in §63.746 shall record 

the information specified in paragraphs (e)(1) through (e)(7) of 

this section, as appropriate. 

(1) General. For all chemical strippers used in the 

depainting operation: 
Page 140 of 174

(i) The name of each chemical stripper; and 

(ii) Monthly volumes of each organic HAP containing 

chemical stripper used or monthly weight of organic HAP-material 

used for spot stripping and decal removal.

(2) For HAP-containing chemical strippers that are 

controlled by a carbon adsorber: 

(i) The overall control efficiency of the control system 

(as determined using the procedures specified in §63.750(g)) and 

all test results, data, and calculations used in determining the 

overall control efficiency. The length of the rolling material 

balance period and all data and calculations used for 

determining this rolling period. The record of the certification 

of the accuracy of the device that measures the amount of HAP or 

VOC recovered; or 

(ii) For nonregenerative carbon adsorbers, the overall 

control efficiency of the control system (as determined using 

the procedures specified in §63.750(g)) and all test results, 

data, and calculations used in determining the overall control 

efficiency. The record of the carbon replacement time 

established as the site-specific operating parameter to 

demonstrate compliance. 

(3) For HAP-containing chemical strippers that are 

controlled by a control device other than a carbon adsorber: 
Page 141 of 174

(i) The overall control efficiency of the control system 

(as determined using the procedures specified in §63.750(h)) and 

all test results, data, and calculations used in determining the 

overall control efficiency; 

(ii) [Reserved]

(4) For each type of aircraft depainted at the facility, a 

listing of the parts, subassemblies, and assemblies normally 

removed from the aircraft before depainting. Prototype, test 

model or aircraft that exist in low numbers (i.e., less than 25 

aircraft of any one type) are exempt from this requirement. 

(5) Non-chemical based equipment. If dry media blasting 

equipment is used to comply with the organic HAP emission limit 

specified in §63.746(b)(1): 

(i) The names and types of non-chemical based equipment; 

and 

(ii) For periods of malfunction, 

(A) The non-chemical method or technique that 

malfunctioned; 

(B) The date that the malfunction occurred; 

(C) A description of the malfunction; 

(D) The methods used to depaint aerospace vehicles during 

the malfunction period; 

(E) The dates that these methods were begun and 

discontinued; and 
Page 142 of 174

(F) The date that the malfunction was corrected.

(6) Spot stripping and decal removal. For spot stripping 

and decal removal, the volume of organic HAP-containing chemical 

stripper or weight of organic HAP used, the annual average 

volume of organic HAP-containing chemical stripper or weight of 

organic HAP used per aircraft, the annual number of aircraft 

stripped, and all data and calculations used.

(7) Inorganic HAP emissions. Each owner or operator shall 

record the actual pressure drop across the particulate filters 

or the visual continuity of the water curtain and water flow 

rate for conventional waterwash systems once each shift in which 

the depainting process is in operation. For pumpless waterwash 

systems, the owner or operator shall record the parameter(s) 

recommended by the booth manufacturer that indicate the 

performance of the booth once per shift in which the depainting 

process is in operation. This log shall include the acceptable 

limit(s) of the pressure drop as specified by the filter 

manufacturer, the visual continuity of the water curtain and the 

water flow rate for conventional waterwash systems, or the 

recommended parameter(s) that indicate the booth performance for 

pumpless systems as specified by the booth manufacturer or in 

locally prepared operating procedures.

(f) Chemical milling maskant application operations. Each 

owner or operator seeking to comply with the organic HAP and VOC 
Page 143 of 174

content limits for the chemical milling maskant application 

operation, as specified in §63.747(c), or the control system 

requirements specified in §63.747(d), shall record the 

information specified in paragraphs (f)(1) through (f)(4) of 

this section, as appropriate. Each owner and operator using 

coating manufacturer’s supplied data to demonstrate compliance 

with the applicable organic HAP or VOC limit specified in § 

63.747(c) may retain the manufacturer’s documentation and annual 

purchase records in place of the records specified in paragraph 

(f)(1) of this section.

(1) For uncontrolled chemical milling maskants that meet 

the organic HAP or VOC content limit without averaging: 

(i) The mass of organic HAP emitted per unit volume of 

chemical milling maskant as applied (less water) (Hi) and the 

mass of VOC emitted per unit volume of chemical milling maskant 

as applied (less water and exempt solvents) (Gi) for each 

chemical milling maskant formulation used each month (as 

determined by the procedures specified in §63.750 (k) and (m)); 

(ii) All data, calculations, and test results (including 

EPA Method 24 results) used in determining the values of Hi and 

Gi; and 

(iii) The volume (gal) of each chemical milling maskant 

formulation used each month. 
Page 144 of 174

(2) For chemical milling maskants complying with the 

organic HAP or VOC content level by averaging: 

(i) The monthly volume-weighted average masses of organic 

HAP emitted per unit volume of chemical milling maskant as 

applied (less water) (Ha) and of VOC emitted per unit volume of 

chemical milling maskant as applied (less water and exempt 

solvents) (Ga) for all chemical milling maskants (as determined 

by the procedures specified in §63.750 (l) and (n)); and 

(ii) All data, calculations, and test results (including 

EPA Method 24 results) used to determine the values of Ha and Ga. 

(3) For chemical milling maskants that are controlled by a 

carbon adsorber: 

(i) The overall control efficiency of the control system 

(as determined using the procedures specified in §63.750(g)) and 

all test results, data, and calculations used in determining the 

overall control efficiency. The length of the rolling material 

balance period and all data and calculations used for 

determining this rolling period. The record of the certification 

of the accuracy of the device that measures the amount of HAP or 

VOC recovered; or 

(ii) For nonregenerative carbon adsorbers, the overall 

control efficiency of the control system (as determined using 

the procedures specified in §63.750(g)) and all test results, 

data, and calculations used in determining the overall control 
Page 145 of 174

efficiency. The record of the carbon replacement time 

established as the site-specific operating parameter to 

demonstrate compliance.

(4) For chemical milling maskants that are controlled by a 

control device other than a carbon adsorber: 

(i) The overall control efficiency of the control system 

(as determined using the procedures specified in §63.750(h)) and 

all test results, data, and calculations used in determining the 

overall control efficiency; 

(ii) If an incinerator other than a catalytic incinerator 

is used, continuous records of the firebox temperature recorded 

under §63.751(b)(9) and all calculated 3-hour averages of the 

firebox temperature; and 

(iii) If a catalytic incinerator is used, continuous 

records of the temperature recorded under §63.751(b)(10) and all 

calculated 3-hour averages of the recorded temperatures.

§ 63.753 Reporting requirements.

(a)(1) Except as provided in paragraphs (a)(2) and 

(a)(3through (a)(5) of this section, each owner or operator 

subject to this subpart shall fulfill the requirements contained 

in § 63.9(a) through (e) and (h) through (j), Notification 

requirements, and § 63.10(a), (b), (d), and (f), Recordkeeping 

and reporting requirements, of the General Provisions, 40 CFR 

part 63, subpart A, and that the initial notification for 
Page 146 of 174

existing sources required in § 63.9(b)(2) shall be submitted not 

later than September 1, 1997, or as specified in § 63.9(b)(2). 

In addition to the requirements of § 63.9(h), the notification 

of compliance status shall include:

(i) Information detailing whether the source has operated 

within the specified ranges of its designated operating 

parameters.

(ii) For each coating line, where averaging will be used 

along with the types of quantities of coatings the facility 

expects to use in the first year of operation. Averaging scheme 

shall be approved by the Administrator or delegated State 

authority and shall be included as part of the facility's title 

V or part 70 permit.

(2) The initial notification for existing sources, required 

in § 63.9(b)(2) shall be submitted no later than September 1, 

1997, or as specified in § 63.9(b)(2). For the purposes of this 

subpart, a title V or part 70 permit application may be used in 

lieu of the initial notification required under § 63.9(b)(2), 

provided the same information is contained in the permit 

application as required by § 63.9(b)(2), and the State to which 

the permit application has been submitted has an approved 

operating permit program under part 70 of this chapter and has 

received delegation of authority from the EPA. Permit 
Page 147 of 174

applications shall be submitted by the same due dates as those 

specified for the initial notifications. 

(3) For the purposes of this subpart, the Administrator 

will notify the owner or operator in writing of approval or 

disapproval of the request for an adjustment to a particular 

time period or postmark deadline submitted under §63.9(i) within 

30 calendar days of receiving sufficient information to evaluate 

the request, rather than 15 calendar days as provided for in 

§63.9(i)(3). 

(4) Each owner or operator subject to this subpart is not 

required to comply with § 63.10(b)(2)(i), (b)(2)(iv), (b)(2)(v), 

and (d)(5).

(5) If a source fails to meet an applicable standard 

specified in §§ 63.744 through 63.748, report such events in the 

semiannual report:

(i) The number of failures to meet an applicable standard. 

(ii) For each instance, report the date, time and duration 

of each failure. 

(iii) For each failure the report must include a list of 

the affected sources or equipment, an estimate of the quantity 

of each regulated pollutant emitted over any emission limit, and 

a description of the method used to estimate the emissions.
Page 148 of 174

(b) Cleaning operation. Each owner or operator of a 

cleaning operation subject to this subpart shall submit the 

following information: 

(1) Semiannual reports occurring every 6 months from the 

date of the notification of compliance status that identify: 

(i) Any instance where a noncompliant cleaning solvent is 

used for a non-exempt hand-wipe cleaning operation; 

(ii) A list of any new cleaning solvents used for hand-wipe 

cleaning in the previous 6 months and, as appropriate, their 

composite vapor pressure or notification that they comply with 

the composition requirements specified in §63.744(b)(1); 

(iii) Any instance where a noncompliant spray gun cleaning

method is used; 

(iv) Any instance where a leaking enclosed spray gun

cleaner remains unrepaired and in use for more than 15 days; and 

(v) If the operations have been in compliance for the 

semiannual period, a statement that the cleaning operations have 

been in compliance with the applicable standards. Sources shall 

also submit a statement of compliance signed by a responsible 

company official certifying that the facility is in compliance 

with all applicable requirements. 

(c) Primer and, topcoat, and specialty coating application 

operations. Each owner or operator of a primer or topcoat 
Page 149 of 174

application operation subject to this subpart shall submit the 

following information: 

(1) Semiannual reports occurring every 6 months from the 

date of the notification of compliance status that identify: 

(i) For primers and, topcoats, and specialty coatings where 

compliance is not being achieved through the use of averaging or 

a control device, the HAP or VOC content in manufacturer’s 

supplied data as recorded under § 63.752(c), or each value of Hi

and Gi, as recorded under §63.752(c)(2)(i), that exceeds the 

applicable organic HAP or VOC content limit specified in §

63.745(c); 

(ii) For primers and, topcoats, and specialty coatings

where compliance is being achieved through the use of averaging, 

each value of Ha and Ga, as recorded under § 63.752(c)(4)(i), 

that exceeds the applicable organic HAP or VOC content limit

specified in § 63.745(c); 

(iii) If incinerators are used to comply with the 

standards, all periods when the 3-hour average combustion 

temperature(s) is (are) less than the average combustion 

temperature(s) established under §63.751(b) (11) or (12) during 

the most recent performance test during which compliance was 

demonstrated; 

(iv) If a carbon adsorber is used; 
Page 150 of 174

(A) each rolling period when the overall control efficiency 

of the control system is calculated to be less than 81%, the 

initial material balance calculation, and any exceedances as 

demonstrated through the calculation; or, 

(B) for nonregenerative carbon adsorbers, submit the design 

evaluation, the continuous monitoring system performance report, 

and any excess emissions as demonstrated through deviations of 

monitored values. 

(v) For control devices other than an incinerator or carbon 

adsorber, each exceedance of the operating parameter(s) 

established for the control device under the initial performance 

test during which compliance was demonstrated; 

(vi) All times when a primer or topcoat application 

operation was not immediately shut down when the pressure drop 

across a dry particulate filter or HEPA filter system, the water 

flow rate through a conventional waterwash system, or the 

recommended parameter(s) that indicate the booth performance for 

pumpless systems, as appropriate, was outside the limit(s) 

specified by the filter or booth manufacturer or in locally 

prepared operating procedures;

(vii) If the operations have been in compliance for the 

semiannual period, a statement that the operations have been in 

compliance with the applicable standards; and, 
Page 151 of 174

(2) Annual reports beginning 12 months after the date of 

the notification of compliance status listing the number of 

times the pressure drop or water flow rate for each dry filter 

or waterwash system, as applicable, was outside the limit(s) 

specified by the filter or booth manufacturer or in locally 

prepared operating procedures. 

(d) Depainting operation. Each owner or operator of a 

depainting operation subject to this subpart shall submit the 

following information: 

(1) Semiannual reports occurring every 6 months from the 

date of the notification of compliance status that identify: 

(i) Any 24-hour period where organic HAP were emitted from 

the depainting of aerospace vehicles, other than from the exempt 

operations listed in §63.746 (a), (b)(3), and (b)(5). 

(ii) Any new chemical strippers used at the facility during 

the reporting period; 

(iii) The organic HAP content of these new chemical 

strippers; 

(iv) For each chemical stripper that undergoes 

reformulation, its organic HAP content; 

(v) Any new non-chemical depainting technique in use at the 

facility since the notification of compliance status or any 

subsequent semiannual report was filed; 

(vi) For periods of malfunctions: 
Page 152 of 174

(A) The non-chemical method or technique that 

malfunctioned; 

(B) The date that the malfunction occurred; 

(C) A description of the malfunction; 

(D) The methods used to depaint aerospace vehicles during 

the malfunction period; 

(E) The dates that these methods were begun and 

discontinued; and 

(F) The date that the malfunction was corrected; 

(vii) All periods where a nonchemical depainting operation 

subject to §63.746(b)(2) and (b)(4) for the control of inorganic 

HAP emissions was not immediately shut down when the pressure 

drop, water flow rate, or recommended booth parameter(s) was 

outside the limit(s) specified by the filter or booth 

manufacturer or in locally prepared operational procedures;

(viii) A list of new and discontinued aircraft models 

depainted at the facility over the last 6 months and a list of 

the parts normally removed for depainting for each new aircraft 

model being depainted; and 

(ix) If the depainting operation has been in compliance for 

the semiannual period, a statement signed by a responsible 

company official that the operation was in compliance with the 

applicable standards. 
Page 153 of 174

(2) Annual reports occurring every 12 months from the date 

of the notification of compliance status that identify: 

(i) The average volume per aircraft of organic HAPcontaining chemical strippers or weight of organic HAP used for 

spot stripping and decal removal operations if it exceeds the 

limits specified in §63.746(b)(3); and

(ii) The number of times the pressure drop limit(s) for 

each filter system or the number of times the water flow rate 

limit(s) for each waterwash system were outside the limit(s) 

specified by the filter or booth manufacturer or in locally 

prepared operating procedures. 

(3) Where a control device is used to control organic HAP 

emissions, semiannual reports that identify: 

(i) If a carbon adsorber is used, 

(A) each rolling period when the overall control efficiency 

of the control system is calculated to be less than 81% for 

existing systems or less than 95% for new systems, the initial 

material balance calculation, and any exceedances as 

demonstrated through the calculation; or, 

(B) for nonregenerative carbon adsorbers, submit the design 

evaluation, the continuous monitoring system performance report, 

and any excess emissions as demonstrated through deviations of 

monitored values. 
Page 154 of 174

(ii) For control devices other than a carbon adsorber, each 

exceedance of the operating parameter(s) established for the 

control device under the initial performance test during which 

compliance was demonstrated; 

(iii) Descriptions of any control devices currently in use 

that were not listed in the notification of compliance status or 

any subsequent report. 

(e) Chemical milling maskant application operation. Each 

owner or operator of a chemical milling maskant application 

operation subject to this subpart shall submit semiannual 

reports occurring every 6 months from the date of the 

notification of compliance status that identify: 

(1) For chemical milling maskants where compliance is not 

being achieved through the use of averaging or a control device, 

the HAP or VOC content in manufacturer’s supplied data as 

recorded under § 63.752(f), or each value of Hi and Gi, as 

recorded under §63.752(f)(1)(i), that exceeds the applicable 

organic HAP or VOC content limit specified in §63.747(c); 

(2) For chemical milling maskants where compliance is being 

achieved through the use of averaging, each value of Ha and Ga, 

as recorded under §63.752(f)(2)(i), that exceeds the applicable 

organic HAP or VOC content limit specified in §63.747(c); 

(3) Where a control device is used, 
Page 155 of 174

(i) If incinerators are used to comply with the standards, 

all periods when the 3-hour average combustion temperature(s) is 

(are) less than the average combustion temperature(s) 

established under §63.751(b) (11) or (12) during the most recent 

performance test during which compliance was demonstrated; 

(ii) If a carbon adsorber is used, 

(A) Each rolling period when the overall control efficiency 

of the control system is calculated to be less than 81%, the 

initial material balance calculation, and any exceedances as 

demonstrated through the calculation; or, 

(B) For nonregenerative carbon adsorbers, submit the design 

evaluation, the continuous monitoring system performance report, 

and any excess emissions as demonstrated through deviations of 

monitored values. 

(iii) For control devices other than an incinerator or 

carbon adsorber, each exceedance of the operating parameter(s) 

established for the control device under the initial performance 

test during which compliance was demonstrated;

(4) All chemical milling maskants currently in use that 

were not listed in the notification of compliance status or any 

other subsequent semiannual report; 

(5) Descriptions of any control devices currently in use 

that were not listed in the notification of compliance status or 

any subsequent report; and 
Page 156 of 174

(6) If the operations have been in compliance for the 

semiannual period, a statement that the chemical milling maskant 

application operation has been in compliance with the applicable 

standards. 

§§63.754-63.758 [Reserved]

§63.759 Implementation and enforcement.

(a) This subpart can be implemented and enforced by the 

U.S. EPA, or a delegated authority such as the applicable State, 

local, or Tribal agency. If the U.S. EPA Administrator has 

delegated authority to a State, local, or Tribal agency, then 

that agency, in addition to the U.S. EPA, has the authority to 

implement and enforce this subpart. Contact the applicable U.S. 

EPA Regional Office to find out if implementation and 

enforcement of this subpart is delegated to a State, local, or 

Tribal agency.

(b) In delegating implementation and enforcement authority 

of this subpart to a State, local, or Tribal agency under 

subpart E of this part, the authorities contained in paragraph 

(c) of this section are retained by the Administrator of U.S. 

EPA and cannot be transferred to the State, local, or Tribal 

agency.

(c) The authorities that cannot be delegated to State, 

local, or Tribal agencies are as specified in paragraphs (c)(1) 

through (4) of this section.
Page 157 of 174

(1) Approval of alternatives to the requirements in 

§§63.741, 63.743, 63.744(a)(3), (b) through (e), 63.745 through 

63.748, and 63.649(a).

(2) Approval of major alternatives to test methods under 

§63.7(e)(2)(ii) and (f), as defined in §63.90, and as required 

in this subpart.

(3) Approval of major alternatives to monitoring under 

§63.8(f), as defined in §63.90, and as required in this subpart.

(4) Approval of major alternatives to recordkeeping and 

reporting under §63.10(f), as defined in §63.90, and as required 

in this subpart.

Table 1 to Subpart GG of Part 63—General Provisions 

Applicability to Subpart GG

Reference

Applies to 

affected sources 

in subpart GG Comment

63.1(a)(1) Yes

63.1(a)(2) Yes

63.1(a)(3) Yes

63.1(a)(4) Yes

63.1(a)(5) No Reserved.

63.1(a)(6) Yes

63.1(a)(7) Yes

63.1(a)(8) Yes

63.1(a)(9) No Reserved.

63.1(a)(10) Yes

63.1(a)(11) Yes

63.1(a)(12) Yes

63.1(a)(13) Yes
Page 158 of 174

Reference

Applies to 

affected sources 

in subpart GG Comment

63.1(a)(14) Yes

63.1(b)(1) Yes

63.1(b)(2) Yes

63.1(b)(3) Yes

63.1(c)(1) Yes

63.1(c)(2) Yes Subpart GG does not apply to area 

sources.

63.1(c)(3) No Reserved.

63.1(c)(4) Yes

63.1(c)(5) Yes

63.1(d) No Reserved.

63.1(e) Yes

63.2 Yes

63.3 Yes

63.4(a)(1) Yes

63.4(a)(2) Yes

63.4(a)(3) Yes

63.4(a)(4) No Reserved.

63.4(a)(5) Yes

63.4(b) Yes

63.4(c) Yes

63.5(a) Yes

63.5(b)(1) Yes

63.5(b)(2) No Reserved.

63.5(b)(3) Yes

63.5(b)(4) Yes

63.5(b)(5) Yes

63.5(b)(6) Yes

63.5(c) No Reserved.

63.5(d)(1)(i) Yes
Page 159 of 174

Reference

Applies to 

affected sources 

in subpart GG Comment

63.5(d)(1)(ii)(A)-

(H)

Yes

63.5(d)(1)(ii)(I) No Reserved.

63.5(d)(1)(ii)(J) Yes

63.5(d)(1)(iii) Yes

63.5(d)(2)-(4) Yes

63.5(e) Yes

63.5(f) Yes

63.6(a) Yes

63.6(b)(1)-(5) Yes §63.749(a) specifies compliance 

dates for new sources.

63.6(b)(6) No Reserved.

63.6(b)(7) Yes

63.6(c)(1) Yes

63.6(c)(2) No The standards in subpart GG are 

promulgated under section 112(d) 

of the Act.

63.6(c)(3)-(4) No Reserved.

63.6(c)(5) Yes

63.6(d) No Reserved.

63.6(e)(1)(i) YesNo See § 63.743(b) includes 

additional provisionse) for the 

operation and maintenance 

plan.general duty requirement. 

63.6(e)(1)(ii) No

63.6(e)(2) No Section reserved.

63.6(e)(3) No

63.6(f)(1) No

63.6(f)(2)-(f)(3) Yes

63.6(g) Yes

63.6(h) No The standards in subpart GG do not 

include opacity standards.

63.6(i)(1)-(3) Yes
Page 160 of 174

Reference

Applies to 

affected sources 

in subpart GG Comment

63.6(i)(4)(i)(A) Yes

63.6(i)(4)(i)(B) No § 63.743(a)(4) specifies that 

requests for extension of 

compliance must be submitted no 

later than 120 days before an 

affected source's compliance date.

63.6(i)(4)(ii) No The standards in subpart GG are 

promulgated under section 112(d) 

of the Act.

63.6(i)(5)-(12) Yes

63.6(i)(13) Yes

63.6(i)(14) Yes

63.6(i)(15) No Reserved.

63.6(i)(16) Yes

63.6(j) Yes

63.7(a)(1) Yes

63.7(a)(2)(i)-(vi) Yes

63.7(a)(2)(vii)-

(viii)

No Reserved.

63.7(a)(2)(ix) Yes

63.7(a)(3) Yes

63.7(b) Yes

63.7(c) Yes

63.7(d) Yes

63.7(e)(1) YesNo See § 63.749(j). 

63.7(e)(2)-(4) Yes

63.7(f) Yes

63.7(g)(1) Yes

63.7(g)(2) No Reserved.

63.7(g)(3) Yes

63.7(h) Yes

63.8(a)(1)-(2) Yes
Page 161 of 174

Reference

Applies to 

affected sources 

in subpart GG Comment

63.8(a)(3) No Reserved.

63.8(a)(4) Yes

63.8(b) Yes

63.8(c)(1)(i) No

63.8(c)(1)(ii) Yes

63.8(c)(1)(iii) No

63.8(c)(2)-(d)(2) Yes

63.8(d)(3) No

63.8(e)(1)-(4) Yes

63.8(e)(5)(i) Yes

63.8(e)(5)(ii) No The standards in subpart GG do not 

include opacity standards.

63.8(f)(1) Yes

63.8(f)(2)(i)-(vii)Yes

63.8(f)(2)(viii) No The standards in subpart GG do not 

include opacity standards.

63.8(f)(2)(ix) Yes

63.8(f)(3)-(6) Yes

63.8(g) Yes

63.9(a) Yes

63.9(b)(1) Yes

63.9(b)(2) Yes § 63.753(a)(1) requires submittal 

of the initial notification at 

least 1 year prior to the 

compliance date; §63.753(a)(2) 

allows a title V or part 70 permit 

application to be substituted for 

the initial notification in 

certain circumstances.

63.9(b)(3) Yes

63.9(b)(4) Yes

63.9(b)(5) Yes

63.9(c) Yes
Page 162 of 174

Reference

Applies to 

affected sources 

in subpart GG Comment

63.9(d) Yes

63.9(e) Yes

63.9(f) No The standards in subpart GG do not 

include opacity standards.

63.9(g)(1) No

63.9(g)(2) No The standards in subpart GG do not 

include opacity standards.

63.9(g)(3) No

63.9(h)(1)-(3) Yes § 63.753(a)(1) also specifies 

additional information to be 

included in the notification of 

compliance status.

63.9(h)(4) No Reserved.

63.9(h)(5)-(6) Yes

63.9(i) Yes

63.9(j) Yes

63.10(a) Yes

63.10(b)(1) Yes

63.10(b)(2)(i) No

63.10(b)(2)(ii) No See § 63.752(a) for recordkeeping 

of (1) date, time and duration; 

(2) listing of affected source or 

equipment, and an estimate of the 

quantity of each regulated 

pollutant emitted over the 

standard; and (3) actions to 

minimize emissions and correct the 

failure.

63.10(b)(2)(iii) Yes

63.10(b)(2)(iv)-(v)No

63.10(b)(2)(vi) Yes

63.10(b)(2)(vi)(A)-

(C)

YesNo § 63.10(b)(vii)(A), (B) and (C) do 

not apply because subpart GG does 

not require the use of CEMS.

63.10(b)(2)(vii)-

(xiv)
Page 163 of 174

Reference

Applies to 

affected sources 

in subpart GG Comment

63.10(b)(3) Yes

63.10(c)(1) No

63.10(c)(2)-(4) No Reserved.

63.10(c)(5)-(86) No

63.10(c)(7)-(8) Yes

63.10(c)(9) No Reserved.

63.10(c)(10)-(13) No

63.10(c)(14) No § 63.8(d) does not apply to this 

subpart.

63.10(c)(15) No

63.10(d)(1)-(2) Yes

63.10(d)(3) No The standards in subpart GG do not 

include opacity standards.

63.10(d)(4) Yes

63.10(d)(5) YesNo. See § 

63.753 (a)(5) for 

malfunction 

reporting 

requirements. 

63.(10)(e)(1) No

63.10(e)(2)(i) No

63.10(e)(2)(ii) No The standards in subpart GG do not 

include opacity standards.

63.10(e)(3) No

63.10(e)(4) No The standards in subpart GG do not 

include opacity standards.

63.10(f) Yes

63.11 Yes

63.12 Yes

63.13 Yes

63.14 Yes

63.15 Yes

63.16 Yes
Page 164 of 174

Appendix A to Subpart GG of Part 63—Specialty Coating 

Definitions

Ablative coating—A coating that chars when exposed to open 

flame or extreme temperatures, as would occur during the failure 

of an engine casing or during aerodynamic heating. The ablative 

char surface serves as an insulative barrier, protecting 

adjacent components from the heat or open flame.

Adhesion promoter—A very thin coating applied to a 

substrate to promote wetting and form a chemical bond with the 

subsequently applied material.

Adhesive bonding primer—A primer applied in a thin film to 

aerospace components for the purpose of corrosion inhibition and 

increased adhesive bond strength by attachment. There are two 

categories of adhesive bonding primers: primers with a design 

cure at 250 °F or below and primers with a design cure above 250 

°F.

Aerosol coating—A hand-held, pressurized, nonrefillable 

container that expels an adhesive or a coating in a finely 

divided spray when a valve on the container is depressed.

Antichafe coating—A coating applied to areas of moving 

aerospace components that may rub during normal operations or 

installation.
Page 165 of 174

Bearing coating—A coating applied to an antifriction 

bearing, a bearing housing, or the area adjacent to such a 

bearing in order to facilitate bearing function or to protect 

base material from excessive wear. A material shall not be 

classified as a bearing coating if it can also be classified as 

a dry lubricative material or a solid film lubricant.

Bonding maskant—A temporary coating used to protect 

selected areas of aerospace parts from strong acid or alkaline 

solutions during processing for bonding.

Caulking and smoothing compounds—Semi-solid materials which 

are applied by hand application methods and are used to 

aerodynamically smooth exterior vehicle surfaces or fill 

cavities such as bolt hole accesses. A material shall not be 

classified as a caulking and smoothing compound if it can also 

be classified as a sealant.

Chemical agent-resistant coating (CARC)—An exterior topcoat 

designed to withstand exposure to chemical warfare agents or the 

decontaminants used on these agents.

Clear coating—A transparent coating usually applied over a 

colored opaque coating, metallic substrate, or placard to give 

improved gloss and protection to the color coat. In some cases, 

a clearcoat refers to any transparent coating without regard to 

substrate.
Page 166 of 174

Commercial exterior aerodynamic structure primer—A primer 

used on aerodynamic components and structures that protrude from 

the fuselage, such as wings and attached components, control 

surfaces, horizontal stabilizers, vertical fins, wing-to-body 

fairings, antennae, and landing gear and doors, for the purpose 

of extended corrosion protection and enhanced adhesion.

Commercial interior adhesive—Materials used in the bonding 

of passenger cabin interior components. These components must 

meet the FAA fireworthiness requirements.

Compatible substrate primer—Includes two categories: 

compatible epoxy primer and adhesive primer. Compatible epoxy 

primer is primer that is compatible with the filled elastomeric 

coating and is epoxy based. The compatible substrate primer is 

an epoxy-polyamide primer used to promote adhesion of 

elastomeric coatings such as impact-resistant coatings. Adhesive 

primer is a coating that (1) inhibits corrosion and serves as a 

primer applied to bare metal surfaces or prior to adhesive 

application, or (2) is applied to surfaces that can be expected 

to contain fuel. Fuel tank coatings are excluded from this 

category.

Corrosion prevention system—A coating system that provides 

corrosion protection by displacing water and penetrating mating 

surfaces, forming a protective barrier between the metal surface 
Page 167 of 174

and moisture. Coatings containing oils or waxes are excluded 

from this category.

Critical use and line sealer maskant—A temporary coating, 

not covered under other maskant categories, used to protect 

selected areas of aerospace parts from strong acid or alkaline 

solutions such as those used in anodizing, plating, chemical 

milling and processing of magnesium, titanium, high-strength 

steel, high-precision aluminum chemical milling of deep cuts, 

and aluminum chemical milling of complex shapes. Materials used 

for repairs or to bridge gaps left by scribing operations (i.e. 

line sealer) are also included in this category.

Cryogenic flexible primer—A primer designed to provide 

corrosion resistance, flexibility, and adhesion of subsequent 

coating systems when exposed to loads up to and surpassing the 

yield point of the substrate at cryogenic temperatures (−275 °F 

and below).

Cryoprotective coating—A coating that insulates cryogenic 

or subcooled surfaces to limit propellant boil-off, maintain 

structural integrity of metallic structures during ascent or reentry, and prevent ice formation.

Cyanoacrylate adhesive—A fast-setting, single component 

adhesive that cures at room temperature. Also known as “super 

glue.”
Page 168 of 174

Dry lubricative material—A coating consisting of lauric 

acid, cetyl alcohol, waxes, or other non-cross linked or resinbound materials which act as a dry lubricant.

Electric or radiation-effect coating—A coating or coating 

system engineered to interact, through absorption or reflection, 

with specific regions of the electromagnetic energy spectrum, 

such as the ultraviolet, visible, infrared, or microwave 

regions. Uses include, but are not limited to, lightning strike 

protection, electromagnetic pulse (EMP) protection, and radar 

avoidance. Coatings that have been designated as “classified” by 

the Department of Defense are exempt.

Electrostatic discharge and electromagnetic interference 

(EMI) coating—A coating applied to space vehicles, missiles, 

aircraft radomes, and helicopter blades to disperse static 

energy or reduce electromagnetic interference.

Elevated-temperature Skydrol-resistant commercial primer—A 

primer applied primarily to commercial aircraft (or commercial 

aircraft adapted for military use) that must withstand immersion 

in phosphate-ester (PE) hydraulic fluid (Skydrol 500b or 

equivalent) at the elevated temperature of 150 °F for 1,000 

hours.

Epoxy polyamide topcoat—A coating used where harder films 

are required or in some areas where engraving is accomplished in 

camouflage colors.
Page 169 of 174

Fire-resistant (interior) coating—For civilian aircraft, 

fire-resistant interior coatings are used on passenger cabin 

interior parts that are subject to the FAA fireworthiness 

requirements. For military aircraft, fire-resistant interior 

coatings are used on parts subject to the flammability 

requirements of MIL-STD-1630A and MIL-A-87721. For space 

applications, these coatings are used on parts subject to the 

flammability requirements of SE-R-0006 and SSP 30233.

Flexible primer—A primer that meets flexibility 

requirements such as those needed for adhesive bond primed 

fastener heads or on surfaces expected to contain fuel. The 

flexible coating is required because it provides a compatible, 

flexible substrate over bonded sheet rubber and rubber-type 

coatings as well as a flexible bridge between the fasteners, 

skin, and skin-to-skin joints on outer aircraft skins. This 

flexible bridge allows more topcoat flexibility around fasteners 

and decreases the chance of the topcoat cracking around the 

fasteners. The result is better corrosion resistance.

Flight test coating—A coating applied to aircraft other 

than missiles or single-use aircraft prior to flight testing to 

protect the aircraft from corrosion and to provide required 

marking during flight test evaluation.
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Fuel tank adhesive—An adhesive used to bond components 

exposed to fuel and that must be compatible with fuel tank 

coatings.

Fuel tank coating—A coating applied to fuel tank components 

to inhibit corrosion and/or bacterial growth and to assure 

sealant adhesion in extreme environmental conditions.

High temperature coating—A coating designed to withstand 

temperatures of more than 350 °F.

Insulation covering—Material that is applied to foam 

insulation to protect the insulation from mechanical or 

environmental damage.

Intermediate release coating—A thin coating applied beneath 

topcoats to assist in removing the topcoat in depainting 

operations and generally to allow the use of less hazardous 

depainting methods.

Lacquer—A clear or pigmented coating formulated with a 

nitrocellulose or synthetic resin to dry by evaporation without 

a chemical reaction. Lacquers are resoluble in their original 

solvent.

Metalized epoxy coating—A coating that contains relatively 

large quantities of metallic pigmentation for appearance and/or 

added protection.

Mold release—A coating applied to a mold surface to prevent 

the molded piece from sticking to the mold as it is removed.
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Nonstructural adhesive—An adhesive that bonds nonload 

bearing aerospace components in noncritical applications and is 

not covered in any other specialty adhesive categories.

Optical anti-reflection coating—A coating with a low 

reflectance in the infrared and visible wavelength ranges, which 

is used for anti-reflection on or near optical and laser 

hardware.

Part marking coating—Coatings or inks used to make 

identifying markings on materials, components, and/or 

assemblies. These markings may be either permanent or temporary.

Pretreatment coating—An organic coating that contains at 

least 0.5 percent acids by weight and is applied directly to 

metal or composite surfaces to provide surface etching, 

corrosion resistance, adhesion, and ease of stripping.

Rain erosion-resistant coating—A coating or coating system 

used to protect the leading edges of parts such as flaps, 

stabilizers, radomes, engine inlet nacelles, etc. against 

erosion caused by rain impact during flight.

Rocket motor bonding adhesive—An adhesive used in rocket 

motor bonding applications.

Rocket motor nozzle coating—A catalyzed epoxy coating 

system used in elevated temperature applications on rocket motor 

nozzles.
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Rubber-based adhesive—Quick setting contact cements that 

provide a strong, yet flexible, bond between two mating surfaces 

that may be of dissimilar materials.

Scale inhibitor—A coating that is applied to the surface of 

a part prior to thermal processing to inhibit the formation of 

scale.

Screen print ink—Inks used in screen printing processes 

during fabrication of decorative laminates and decals.

Seal coat maskant—An overcoat applied over a maskant to 

improve abrasion and chemical resistance during production 

operations.

Sealant—A material used to prevent the intrusion of water, 

fuel, air, or other liquids or solids from certain areas of 

aerospace vehicles or components. There are two categories of 

sealants: extrudable/rollable/brushable sealants and sprayable 

sealants.

Silicone insulation material—Insulating material applied to 

exterior metal surfaces for protection from high temperatures 

caused by atmospheric friction or engine exhaust. These 

materials differ from ablative coatings in that they are not 

“sacrificial.”

Solid film lubricant—A very thin coating consisting of a 

binder system containing as its chief pigment material one or 

more of the following: molybdenum, graphite, 
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polytetrafluoroethylene (PTFE), or other solids that act as a 

dry lubricant between faying surfaces.

Specialized function coatings—Coatings that fulfill 

extremely specific engineering requirements that are limited in 

application and are characterized by low volume usage. This 

category excludes coatings covered in other Specialty Coating 

categories.

Structural autoclavable adhesive—An adhesive used to bond 

load-carrying aerospace components that is cured by heat and 

pressure in an autoclave.

Structural nonautoclavable adhesive—An adhesive cured under 

ambient conditions that is used to bond load-carrying aerospace 

components or for other critical functions, such as 

nonstructural bonding in the proximity of engines.

Temporary protective coating—A coating applied to provide 

scratch or corrosion protection during manufacturing, storage, 

or transportation. Two types include peelable protective 

coatings and alkaline removable coatings. These materials are 

not intended to protect against strong acid or alkaline 

solutions. Coatings that provide this type of protection from 

chemical processing are not included in this category.

Thermal control coating—Coatings formulated with specific 

thermal conductive or radiative properties to permit temperature 

control of the substrate.
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Touch-up and Repair Coating—A coating used to cover minor 

coating imperfections appearing after the main coating 

operation.

Wet fastener installation coating—A primer or sealant 

applied by dipping, brushing, or daubing to fasteners that are 

installed before the coating is cured.

Wing coating—A corrosion-resistant topcoat that is 

resilient enough to withstand the flexing of the wings.