SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT 

APPENDIX F: CTG June 16, 2011 

Final Draft Staff Report with Appendices 

 For Proposed Amendments to Rule 4605

F-1

APPENDIX F 

 1997 EPA Control of Volatile Organic Compound Emissions 

from Coating Operations at 

Aerospace Manufacturing and Reworking Operations 

June 16, 2011 
SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT 

APPENDIX F: CTG June 16, 2011 

Final Draft Staff Report with Appendices 

 For Proposed Amendments to Rule 4605

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This page intentionally blank. 
Printed on Recycled Paper

 United States Office of Air Quality EPA-453/R-97-004

Environmental Protection Planning and Standards December 1997

Agency Research Triangle Park, NC 27711

Air

EPA Guideline Series

Control of Volatile Organic

Compound Emissions from

Coating Operations at Aerospace

Manufacturing and Rework

Operations

APPENDIX F: CTGSAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT June 16, 2011 F - 3 Final Draft Staff Report with Appendices 

For Proposed Amendmetns to Rule 4605
Guideline Series:

Control of Volatile Organic Compound

Emissions from Coating Operations at

Aerospace Manufacturing and Rework

Operations

Emission Standards Division

U. S. Environmental Protection Agency

Office of Air and Radiation

Office of Air Quality Planning and Standards

Research Triangle Park, NC 27711

December 1997

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This report has been reviewed by the Emission Standards

Division of the Office of Air Quality Planning and Standards, EPA

and approved for final publication. Mention of trade names or

commercial products is not intended to constitute endorsement or

recommendation for use. The guideline series of reports is

issued by the Office of Air Quality Planning and Standards

(OAQPS) to provide information to State and local air pollution

control agencies; for example, to provide guidance on the

acquisition and processing of air quality data and on the

planning and analysis requisite for the maintenance of air

quality. Reports published in this series will be available from

the Library Services Office (MD-35), U. S. Environmental

Protection Agency, Research Triangle Park, North Carolina 27711;

from the Office of Air Quality Planning and Standards Technology

Transfer Network, U. S. Environmental Protection Agency, Research

Triangle Park, North Carolina 27711; or, for a fee, from the

National Technical Information Services, 5285 Port Royal Road,

Springfield, Virginia 22161.

Publication No. EPA-453/R-97-004

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TABLE OF CONTENTS

Page

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . 1-1

2.0 AEROSPACE MANUFACTURING AND REWORK OPERATIONS . . . 2-1

2.1 GENERAL . . . . . . . . . . . . . . . . . . . . 2-1

2.2 PROCESS DESCRIPTION . . . . . . . . . . . . . . 2-3

2.2.1 Coating Application . . . . . . . . . . 2-3

2.2.2 Cleaning . . . . . . . . . . . . . . . . 2-6

3.0 EMISSION CONTROL TECHNIQUES . . . . . . . . . . . . 3-1

3.1 COATING SUBSTITUTIONS . . . . . . . . . . . . . 3-1

3.2 EQUIPMENT CHANGES . . . . . . . . . . . . . . . 3-2

3.2.1 High Transfer Efficiency Spray Guns . . 3-2

3.2.2 Spray Gun Cleaning . . . . . . . . . . . 3-5

3.2.3 Conventional High Transfer Efficiency

Application Methods . . . . . . . . . . 3-6

3.3 HAND-WIPE CLEANER SUBSTITUTIONS . . . . . . . . 3-7

3.3.1 Aqueous and Semiaqueous . . . . . . . . 3-7

3.3.2 Citrus-Based . . . . . . . . . . . . . . 3-7

3.3.3 Reduced Vapor Pressure . . . . . . . . . 3-8

4.0 PRESUMPTIVE RACT REQUIREMENTS . . . . . . . . . . . 4-1

4.1 SPECIALTY COATINGS . . . . . . . . . . . . . . 4-1

4.2 PRIMERS, TOPCOATS, CHEMICAL MILLING

MASKANTS . . . . . . . . . . . . . . . . . . . 4-3

4.3 APPLICATION EQUIPMENT . . . . . . . . . . . . . 4-3

4.3.1 Exemptions . . . . . . . . . . . . . . . 4-3

4.3.2 Timing (Schedule) of Compliance . . . . 4-4

4.4 CLEANING OPERATIONS . . . . . . . . . . . . . . 4-4

4.4.1 Housekeeping . . . . . . . . . . . . . . 4-4

4.4.2 Hand-Wipe Cleaning . . . . . . . . . . . 4-5

4.4.3 Flush Cleaning . . . . . . . . . . . . . 4-6

4.4.4 Spray Gun Cleaning . . . . . . . . . . . 4-6

5.0 GUIDANCE TO STATE ENFORCEMENT AGENCIES . . . . . . . 5-1

5.1 DEFINITIONS . . . . . . . . . . . . . . . . . . 5-1

5.2 APPLICABILITY . . . . . . . . . . . . . . . . . 5-2

5.3 COMPLIANCE, MONITORING, RECORDKEEPING & 

REPORTING PROVISIONS . . . . . . . . . . . . . 5-2

APPENDIX A DEFINITIONS . . . . . . . . . . . . . . A-1

APPENDIX B AEROSPACE MANUFACTURING AND REWORK

OPERATIONS MODEL RULE . . . . . . . . . B-1

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LIST OF FIGURES

Page

Figure 2-1. Active U.S. aerospace manufacturing 

facilities . . . . . . . . . . . . . . . . . 2-4

LIST OF TABLES

Page

TABLE 2-1. AEROSPACE MANUFACTURING SIC CODES . . . . . 2-2

TABLE 3-1. PERCENT REDUCTION IN COATING (PRIMERS

AND TOPCOATS) EMISSIONS WITH HIGH

TRANSFER EFFICIENCY EQUIPMENT FROM 

SECTION 114 DATA . . . . . . . . . . . . . . 3-4

TABLE 4-1. SPECIALTY COATINGS VOC CONTENT 

LIMITS . . . . . . . . . . . . . . . . . . . 4-2

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1.0 INTRODUCTION

The Clean Air Act (CAA) as amended in 1990 requires that

State implementation plans (SIP's) for certain ozone

nonattainment areas be revised to require the implementation of

reasonably available control technology (RACT) to control

volatile organic compound (VOC) emissions. The U. S.

Environmental Protection Agency (EPA) has defined RACT as the

lowest emission limitation that a particular source is capable of

meeting by the application of control technology that is

reasonably available considering technological and economic

feasibility. The EPA has issued, and is continuing to issue,

control techniques guideline documents (CTG's) that present

feasible RACT control measures for VOC source categories. The

CTG's recommend "presumptive norms" of control for each source

category, but individual sources may have alternative RACT

requirements imposed by making an adequate infeasibility

demonstration (44 FR 53761, September 17, 1979).

Section 183(b)(3) of the CAA requires the EPA Administrator

to issue a CTG for the control of VOC emissions from coatings and

solvents used in the aerospace industry. This CTG is intended to

supersede any potential applicability of the Miscellaneous Metal

Part and Products CTG (RACT) requirements for manufacturing and

rework operations of aerospace vehicles and components. 

According to the CAA, this CTG guidance should also reflect

control resulting from applying the "best available control (BAC)

measures." Section 183(e)(1)(A) defines "BAC" as the "most

effective equipment, measures, processes, methods, systems or

techniques, including chemical reformulation, product or

feedstock substitution, repackaging, and directions for use,

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consumption, storage, or disposal." Therefore, this CTG departs

from the approach followed in the other CTG's by not recommending

a single approach for determining RACT, but investigating a range

of approaches to reduce VOC emissions from aerospace operations. 

Several optional approaches comprise the presumptive RACT found

in this CTG.

The CTG's are intended to provide State and local air

pollution control authorities with an information base for

proceeding with their analyses of RACT for their own regulations. 

The CTG's contain a review of current knowledge and data

concerning the technology, impacts, and costs associated with

various emission control techniques. Where applicable, the EPA

recommends that States adopt requirements consistent with the

presumptive RACT. However, these measures are only a

recommendation; States may develop their own RACT requirements on

a case-by-case basis, considering the economic and technical

circumstances of individual sources. It should be noted that no

Federal laws or regulations preclude States from requiring more

stringent controls than those recommended as RACT. A particular

State, for example, may broaden the applicability by revising the

"aerospace vehicle or component" definition to include models,

mock-ups, prototypes, and production equipment such as molds,

jigs, and tooling. Some States may need additional control in

order to meet the national ambient air quality standards (NAAQS)

for ozone in some areas.

This CTG identifies presumptive RACT for controlling VOC

emissions from aerospace coatings and cleaning solvents. 

National emission standards for hazardous air pollutants (NESHAP)

for aerospace manufacturing and rework operations were published

on September 1, 1995 (60 FR 45948). While these final standards

address the reduction of HAP emissions, the control techniques

required by the NESHAP will result in reductions of VOC emissions

as well. In addition, the control techniques required by the

NESHAP are similar to those addressed in this CTG for reducing

VOC emissions. Because the emission reductions, costs, and

environmental impacts have already been determined for major HAP

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sources and are attributed to the NESHAP (see Docket No. A-90-20,

Subcategory II-B), these impacts are not summarized in this CTG.

While the Aerospace NESHAP sets limits for maximum HAP and

VOC content for topcoats, primers, maskants, clean-up solvents,

and cleaning operations, the CTG establishes presumptive RACT

limits for VOC's. The CTG includes requirements for Specialty

Coatings, which are not covered by the Aerospace NESHAP. The

Clean Air Act specifies that solvents will be addressed in the

Aerospace CTG. However, because the CTG is guidance to be

adopted as individual State regulations and SIP's, it does not

specify detailed requirements for monitoring, testing,

recordkeeping, and reporting as the NESHAP has done. Rather, the

States are directed under previous EPA guidance for establishing

RACT (57 FR 13502, April 16, 1992) to develop "enforceable

regulations" containing such requirements. While EPA is

providing an example of such a regulation in the model rule

(Appendix B), this CTG allows States the flexibility to address

those requirements as long as they meet EPA enforceability

criteria.

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2.0 AEROSPACE MANUFACTURING AND REWORK OPERATIONS

2.1 GENERAL

The aerospace industry being evaluated includes all

manufacturing facilities that produce an aerospace vehicle or

component and all facilities that rework or repair these

aerospace products. Aerospace vehicle or component is defined

as, but not limited to, any fabricated part, processed part,

assembly of parts, or completed unit of any aircraft including,

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

and space vehicles. In addition to manufacturing and rework

facilities, some shops may specialize in providing a service,

such as chemical milling, rather than actually producing a

component or assembly. In general, aerospace manufacturing and

rework facilities are covered by the SIC codes listed in

Table 2-1. However, facilities classified under other SIC codes

may be subject to the proposed rule if the facility meets the

definition of a major source and the definition of an aerospace

manufacturing or rework facility.

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TABLE 2-1. AEROSPACE MANUFACTURING SIC CODES

SIC Code Description

3720 Aircraft and Parts

3721 Aircraft

3724 Aircraft Engines and Engine Parts

3728 Aircraft Parts and Equipment

3760 Guided Missiles, Space Vehicles, and Parts

3761 Guided Missiles and Space Vehicles

3764 Space Propulsion Units and Parts

3769 Space Vehicle Equipment

4512 Air Transportation, Scheduled

4581 Airports, Flying Fields, and Services

9711 National Security

Aerospace facilities may be divided into four market

segments: commercial original equipment manufacturers (OEM),

commercial rework facilities, military OEM's, and military rework

facilities. The commercial OEM segment of the market includes

the manufacture of commercial aircraft as well as the production

of business and private aircraft. The military OEM segment of

the market includes military installations and defense

contractors that manufacture aircraft, missiles, rockets,

satellites, and spacecraft. Rework facilities, both commercial

and military, may rework many of the above end products.

Based on information obtained through the Federal Aviation

Administration and the U.S. Department of Commerce - Bureau of

the Census, there are an estimated 2,869 aerospace facilities

that could be subject to this guidance. Of this number,

1,395 produce or rework commercial products, and 1,474 produce or

rework military products. The combined VOC emissions from these

facilities are estimated to be over 213,000 megagrams/year

(Mg/yr) (234,000 tons/yr).

In addition to these facilities, there are numerous

subcontractors that manufacture or rework aerospace vehicles or

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components. The subcontractors may work directly for the OEM or

rework facilities, or indirectly through first line

subcontractors. Because most of these subcontractors perform

various types of work, they are often classified under

non-aerospace SIC codes. Consequently, an estimate of the number

of subcontractors cannot be made. One company alone, however,

employs the services of over 5,000 subcontractors.

Aerospace manufacturing facilities and rework operations

typically are located in or near industrial centers in areas of

medium to high population density. Some States with a large

number of aerospace manufacturers are California, Texas,

Connecticut, Florida, and Washington. Figure 2-1 presents the

number of aerospace manufacturing facilities by State.

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Aerospace manufacturing facilities range in size from small

shops that produce a single aerospace component, such as

propellers, to large corporations that produce the entire

aircraft. Aerospace rework facilities, however, are usually

large facilities that must be able to rework or repair every

facet of several models of large commercial or military aircraft.

The hours of operation at aerospace manufacturing and rework

facilities may vary greatly due to the production backlog at each

facility. The hours of operation may range from 8 hours (or

less) per day, 5 days per week, to 24 hours per day, 7 days per

week. 

2.2 PROCESS DESCRIPTION

Aerospace manufacturing and rework operations typically

consist of the following basic operations: materials receiving,

machining and mechanical processing, coating application,

chemical milling, heat treating, cleaning, metal processing and

finishing, coating removal (depainting), composite processing,

and testing. Many aerospace manufacturing and rework facilities

may employ all of these processes in their operations, as with an

OEM facility that produces the entire aerospace vehicle. 

However, an aerospace facility may only employ a subset of these

operations, as with a facility that produces a single component

or assembly or a facility that provides a service such as

chemical milling. Of these operations, coating application and

cleaning are the significant sources of VOC emissions and are the

processes covered by this Aerospace CTG in the following

sections.

2.2.1 Coating Application

A coating is a material that is applied to the surface of a

part to form a decorative, protective, or functional solid film. 

The most common coatings are the broad categories of

nonspecialized primers and topcoats that are regulated for major

sources under the Aerospace NESHAP. There are also numerous

specialty coatings covered by this guidance that provide 

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Figure 2-1. Active U.S. aerospace manufacturing facilities.

additional performance characteristics, such as temperature,

fluid, fire resistance, flexibility, substrate compatibility,

antireflection, temporary protection or marking, sealing,

adhesively joining substrates, enhanced corrosion protection, or

compatibility with a space environment. Each material is

different because it must meet individual performance standards

particular to a specific design. The quality of the coatings is

critical to the airworthiness and safety of the final product. 

Aerospace vehicle manufacturing is strictly controlled by the

Federal Aviation Administration, the Department of Defense, and

specific customer requirements. Industry specifications for

coatings are dictated by these requirements.

Most aerospace coatings are solvent-borne, which contain a

mixture of organic solvents, many of which are VOC's. The most

common VOC solvents used in coatings are toluene, xylene, methyl

ethyl ketone, and methyl isobutyl ketone. The VOC content ranges

differ for the various coating categories.

2.2.1.1 Sealing. Sealants, predominately composed of

polysulfide, are applied throughout the aerospace vehicle

structure primarily to seal out moisture and contaminants to

prevent corrosion, such as on faying (i.e., closely or tightly

fitting) surfaces, inside holes and slots, and around installed

fasteners. They are also used to seal fuel tanks and pressurized

components. Sealants are applied using tubes, spatulas, brushes,

rollers, or spray guns. Sealants are often stored frozen and

thawed before use, and many are two-component mixtures that cure

after mixing. Typically, a sealant is applied before assembly or

fastener installation, and the excess is squeezed out or extruded

from between the parts as the assembly is completed. This

ensures a moisture-tight seal between the parts.

2.2.1.2 Adhesive Bonding. Adhesive bonding involves

joining together two or more metal or nonmetal components. This

process is typically performed when the joints being formed are

essential to the structural integrity of the aerospace vehicle or

component. Bonding surfaces are typically roughened mechanically

or etched chemically to provide increased surface area for

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bonding and then treated chemically to provide a stable

corrosion-resistant oxide layer. The surfaces are then thinly

coated with an adhesive bonding primer to promote adhesion and

protect from subsequent corrosion. Structural adhesives are

applied as either a thin film or as a paste. The parts are

joined together and cured either at ambient temperature, in an

oven, or in an autoclave to cure the adhesive and provide a

permanent bond between the components.

Nonstructural adhesives are used to bond materials that are

not critical to the structural integrity of the aerospace vehicle

or component, such as gaskets around windows and carpeting or to

nonstructurally joined components. These adhesives are applied

using tubes, brushes, and spray guns. 

2.2.2 Cleaning

Cleaning agents for hand-wipe, flush, and spray equipment

cleaning consist of solvents such as methyl ethyl ketone, methyl

isobutyl ketone, toluene, various solvent blends, or alkaline

materials.

2.2.2.1 Hand-Wipe and Flush Cleaning. Aerospace components

are cleaned frequently during manufacturing to remove

contaminants such as dirt, grease, and oil, and to prepare the

components for the next operation. Cleaning is typically

performed by a hand wiping process using a wide variety of

cleaning solvents. Assemblies and parts with concealed or

inaccessible areas may be flush-cleaned by passing the cleaning

agent over, into, or through the part. The cleaning agent is

then drained from the part and the procedure is repeated as many

times as necessary to ensure the required cleanliness.

2.2.2.2 Spray Gun and Coating Line Cleaning. Spray guns

and coating lines used to apply the various coatings used at

aerospace facilities must be cleaned when switching from one

coating to another and when they are not going to be immediately

reused. Spray guns can be cleaned either manually or with

enclosed spray gun cleaners. Manual cleaning involves

disassembling the gun and placing the parts in a vat containing

an appropriate cleaning solvent. The residual paint is brushed

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or wiped off the parts. After reassembling, the cleaning solvent

may be sprayed through the gun for a final cleaning. Paint

hoses/coating lines are cleaned by passing the cleaning solvent

through the lines until all coating residue is removed.

Enclosed spray gun cleaners are self-contained units that pump

the cleaning solvent through the gun within a closed chamber. 

After the cleaning cycle is complete, the guns are removed from

the chamber and typically undergo some manual cleaning to remove

coating residue from areas not exposed to the cleaning solvent,

such as the seals under the atomizing cap.

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3.0 EMISSION CONTROL TECHNIQUES

The principal technique used by the aerospace industry to

control VOC emissions from coating application and cleaning is

product substitution, which eliminates or reduces the generation

of emissions. The emission reduction is obtained using less

energy and producing less waste than using a control device to

achieve the same emission reductions.

The VOC emissions may be controlled by replacing products

containing high concentrations of VOC's with ones that have

reduced or eliminated VOC's. Different aerospace manufacturers

use different processes to produce their product. Therefore,

they typically have different specifications for the coatings and

cleaning solvents used on the components of the end products. 

Each individual facility must evaluate the ability of the new

product to maintain standards of quality and performance. In

addition, the potential overall environmental benefit of the

reformulated products must be carefully evaluated.

The following sections describe the available product

substitutions for coatings and cleaning solvents. While

alternative methods, such as control devices (carbon adsorbers,

incinerators, etc.), are occasionally used to reduce emissions,

they do not represent RACT and are, therefore, not discussed

below. 

3.1 COATING SUBSTITUTIONS

Waterborne and high solids materials are generally used for

coating substitutions. Specialty coatings typically have

relatively low usage, so reformulation to lower VOC contents does

not produce significant air quality benefits nor is it

economically feasible for the paint suppliers. Paint suppliers

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and the aerospace industry generally have targeted high volume

materials for reformulation efforts. Therefore, lower VOC

formulations are not available for most of the low volume

specialty coating categories. 

3.2 EQUIPMENT CHANGES

The aerospace industry has implemented several equipment

changes that directly reduce the level of VOC emissions. While

there are equipment changes that effect emissions from every

process, the three changes predominantly used in the industry are

high transfer efficiency spray guns, spray gun cleaners, and

conventional high transfer efficiency methods. Each of these

equipment changes are discussed below.

3.2.1 High Transfer Efficiency Spray Guns

Emissions from spray coating operations can be reduced

through the use of spraying systems with higher transfer

efficiency. Transfer efficiency, expressed as a percentage, can

be defined as the ratio of coating solids actually applied to the

surface of the component being coated to the amount of solids

released from the spray gun. Spraying systems with a higher

transfer efficiency can coat the same surface area using less

coating. Therefore, the VOC emissions resulting from the use of

this equipment are reduced compared to applying the same coating

with conventional spray equipment. The transfer efficiency

values reported in this section depend on coating sprayed, part

configuration, spray booth air velocity, and other variables.

Most aerospace components are coated using manual spray

equipment utilizing conventional airspray or airless spraying

technology. The following sections discuss two types of high

transfer coating application equipment generally used in the

aerospace industry for the application of primers and topcoats: 

high volume, low pressure (HVLP) and electrostatic (use of these

types of high transfer efficiency for specialty coatings is

limited).

3.2.1.1 High Volume Low Pressure Spray Guns. High volume

low pressure and electrostatic spraying systems are the primary

high efficiency spray methods used by the industry. High volume

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low pressure spray guns use high volumes [10 to 25 standard cubic

feet per minute (scfm)] of low pressure [2 to 10 pounds per

square inch gauge (psig)] air to deliver the paint. The lower

air pressure creates a lower particle speed, resulting in a more

controlled spray pattern with less overspray and bounce back from

the substrate, thus improving transfer efficiency.

High volume low pressure systems have been in use in the

United States for approximately 10 years. In early systems,

turbines were used to supply a high volume of low pressure air to

the spray guns through large hoses. The second generation used

compressed air with an air regulator to maintain the required low

pressure. The third and current generation of HVLP equipment

uses restrictors within the gun to reduce the atomization

pressure to a maximum of 10 psi at the air cap.

One disadvantage of HVLP spray guns is that some very high

solids coatings are difficult to atomize due to their higher

viscosities. However, when a turbine is used, the temperature of

the atomizing air increases which aids in reducing the viscosity

of the coating. Other disadvantages of HVLP spray guns are that

they cannot be used with extension nozzles, and they may slow

production rates because of the low fluid delivery rates.

It is estimated that HVLP can apply approximately 80 percent

of the coating currently used in the aerospace industry,

including primers, waterborne coatings, and both single and twocomponent topcoats. A medium commercial/rework facility utilizes

HVLP equipment with high solids paint and has had a reduction of

22 to 30 percent in coating usage for various aircraft types. 

The HVLP technology has proven easy to use and maintain. It also

provides high transfer efficiency and appears to be the preferred

spray technology in the aerospace industry at this time.

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Table 3-1

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TABLE 3-1. PERCENT REDUCTION IN COATING EMISSIONS

(PRIMERS AND TOPCOATS) WITH HIGH TRANSFER

EFFICIENCY EQUIPMENT FROM SECTION 114 DATA

Size

Commercial

or military

OEM or

rework

High transfer

equipment

% Reduction in

emissions

Large Military OEM HVLP 20

Large Military OEM HVLP 20

Large Military OEM HVLP 25

Large Commercial OEM Unspecified 30

Large Commercial OEM Unspecified 18

Mediu

m CommercialMilitary

Military

OEM

OEM

Rework

HVLP 25

Mediu

m

Commercial

Military

Military

OEM

OEM

Rework

HVLP 20-40

Mediu

m Military OEM HVLP andelectrostatic

40

Mediu

m Military OEM HVLP andelectrostatic

40

Mediu

m

Military OEM HVLP 40

Mediu

m

Military OEM HVLP 10

Mediu

m

Military

Military

OEM

Rework

Electrostatic 30-40

Mediu

m

Military Rework HVLP and

electrostatic

35-40

Mediu

m

Commercial OEM Unspecified 30

Mediu

m Commercial OEM Unspecified 33

Mediu

m

Commercial Rework HVLP and

electrostatic

50

Mediu

m

Commercial Rework HVLP and high

solids

22% for large

aircraft

25% for medium

aircraft

30% for small

aircraft

Small Commercial OEM Unspecified 30

Small Commercial

Military

OEM

OEM

HVLP 28

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 shows the reduction in emissions obtained from the Section 114

questionnaire responses from various facilities utilizing high

transfer efficiency equipment such as HVLP or electrostatic

equipment, either alone, in conjunction with each other, or, in

one case, HVLP equipment with high solids coatings.

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3.2.1.2 Electrostatic Spray Guns. With electrostatic spray

systems, atomized particles of coating acquire an electric charge

as they pass through a high voltage field at the end of the spray

nozzle. This electric charge causes the particles to be

attracted to the parts being painted, which are electrically

grounded. Although other substrates can be pretreated with

conductive coatings, this technology is primarily used for metal

parts. The electrostatic effect can be utilized in conjunction

with air spray, airless, and air-assisted airless systems to

enhance the transfer efficiencies of these basic technologies. 

See Table 3-1 for examples of percent reduction obtained at

various facilities using electrostatic spray guns or

electrostatic spray guns in combination with HVLP spray guns.

3.2.2 Spray Gun Cleaning

Spray guns are typically cleaned at the end of every job, as

well as between color changes. Manual cleaning of spray guns

involves disassembling the gun and placing the parts in a tray

containing an appropriate cleaning solvent. The residual paint

is brushed or wiped off the parts, then cleaning solvent is

sprayed through the gun after it is reassembled. Various methods

are used to minimize the resulting emissions from spray gun

cleaning and are discussed below.

Enclosed system. Enclosed spray gun cleaners are completely

enclosed units that spray the cleaning solvent through and over

the spray gun. The enclosed unit eliminates most of the exposure

of the cleaning solvent to the air, thereby greatly reducing the

VOC emissions from evaporation.

Nonatomized cleaning. Cleaning solvent is placed in the

pressure pot and forced through the gun with the atomizing cap in

place. No atomizing air is to be used. The cleaning solvent

from the spray gun is directed into a vat, drum, or other waste

container that is closed when not in use.

Disassembled spray gun cleaning. Manual cleaning (described

above) with the components cleaned by hand in a vat, which is

only closed when not in use. Alternatively, the components are

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soaked in a vat, which is closed at all times except when

components are being inserted or removed.

Atomizing cleaning. Cleaning solvent is forced through the

spray gun and the resulting atomized spray is directed into a

waste container that is fitted with a device designed to capture

the atomized solvent emissions.

3.2.3 Conventional High Transfer Efficiency Application Methods

Conventional high transfer efficiency application methods

for primers and topcoats include dip, roll, brush, and flow

coating (use of these methods for specialty coatings is limited). 

These methods are discussed below.

Dip Coating. With dip coating application, parts are

immersed into a tank of coating. The parts are then removed from

the tank and held over it until the excess coating drips back

into the tank. This method is simple and allows many different

parts to be coated with high transfer efficiency. However, dip

coating is limited to parts that can fit into the dip tank. 

Other parts difficult to dip coat could include complex parts

that would trap the coating, allowing unequal coating

thicknesses.

Roll Coating. In roll coating application, a series of

mechanical rollers are used to coat flat surfaces. This method

achieves high efficiency with high rates of application and

automation. However, roll coating is limited to flat parts.

Brush Coating. In brush coating application, brushes and

hand rollers are used to apply the coating manually. This method

is used with operations (e.g., touch-up and detail painting) that

cannot tolerate the overspray associated with spray gun

application. For example, if a facility needs to paint only the

tail section of an airplane, it may be easier to brush coat this

area than to mask the entire plane to protect the rest of the

shell from overspray. This application method typically involves

high labor costs, increased production time, and poor coating

thickness control.

Flow Coating. In flow coating application, the part is

conveyed over a closed sink, and a pumped stream of coating

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gently flows over the surface of the part. The excess coating is

drained into the sink, filtered, and pumped to a holding tank for

reuse. Flow coating is typically limited to flat sheets and

noncritical parts. Coating thickness is difficult to control

using flow coating.

3.3 HAND-WIPE CLEANER SUBSTITUTIONS

Product substitutions for hand-wipe cleaning that are

prevalent in the aerospace industry can be classified as aqueous,

semiaqueous, citrus-based, and reduced vapor pressure. Each

category is discussed below.

3.3.1 Aqueous and Semiaqueous

Aqueous and semiaqueous cleaners contain water as the base

component rather than an organic solvent or mixture of solvents. 

Other components may include corrosion inhibitors, alkalinity

builders, and organic surfactants, depending on the desired soil

removal properties. Aqueous and semiaqueous cleaners have been

used in noncritical areas where strict cleanliness requirements

do not have to be met, or where there are no confined spaces that

may trap residues of the cleaner.

The advantages of using aqueous and semiaqueous cleaning

solvents include reduced VOC emissions. Disadvantages are

increased production time due to slower evaporation rates,

possible decreased efficiency, and possible increase in

wastewater treatment requirements. In addition, aqueous cleaners

may not be applicable to all aerospace parts, especially those

components that have small confined spaces where the cleaner

residues cannot be adequately removed. 

3.3.2 Citrus-Based

Citrus-based terpenes such as d-limonene are the primary

components in many alternative cleaning solutions. While these

solutions have high VOC contents, their vapor pressure is very

low, leading to reduced evaporation rates. These cleaners have

been found to be effective in some cleaning operations except for

cleaning prior to adhesive bonding. Some disadvantages include

possible worker sensitivity, VOC emissions, lack of rinseability

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in water, and increased production time due to slower evaporation

rates. 

3.3.3 Reduced Vapor Pressure

Reduced vapor pressure cleaning solvents have a maximum VOC

composite vapor pressure of 45 millimeters of mercury (mmHg)

at 20°C. Cleaning solvent emissions are reduced because their

lower vapor pressure leads to reduced evaporation rates. These

cleaners are effective in many cleaning operations except for

some limited operations such as cleaning oxygen systems.

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4.0 PRESUMPTIVE RACT REQUIREMENTS

The presumptive RACT requirements for the aerospace

component and vehicle cleaning and coating operations are

described in the following sections. The operations covered by

this CTG shall not be subject to another CTG. The operations and

applications exempted under this CTG shall not be subject to

another CTG. Applicable definitions are included in Appendix A.

These presumptive RACT requirements do not apply to

manufacturing or rework operations involving space vehicles;

rework operations performed on antique aerospace vehicles or

components; or to the following activities where cleaning and

coating of aerospace components and vehicles may take place: 

research and development, quality control, laboratory testing,

and electronic parts and assemblies (except for cleaning and

coating of completed assemblies). 

4.1 SPECIALTY COATINGS

Presumptive RACT for coatings used on aerospace components

and vehicles is based on VOC content. Except as provided in

Sections 4.0 and 4.1, the presumptive RACT for coating VOC

content is the use of coatings with a VOC content less than or

equal to that given in Table 4-1: Specialty Coatings VOC Content

Limits. 

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TABLE 4-1. SPECIALTY COATINGS VOC CONTENT LIMITS (g/L)a

Coating type Limit Coating type Limit

Ablative Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600

Adhesion Promoter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 890

Adhesive Bonding Primers:

Cured at 250°F or below . . . . . . . . . . . . . . . . . . . . . . . . 850

Cured above 250°F ........................... 1030

Adhesives:

Commercial Interior Adhesive . . . . . . . . . . . . . . . . . . . 760

Cyanoacrylate Adhesive . . . . . . . . . . . . . . . . . . . . . . . 1,020

Fuel Tank Adhesive . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620

Nonstructural Adhesive . . . . . . . . . . . . . . . . . . . . . . . . . 360

Rocket Motor Bonding Adhesive . . . . . . . . . . . . . . . . . 890

Rubber-based Adhesive . . . . . . . . . . . . . . . . . . . . . . . . . 850

Structural Autoclavable Adhesive . . . . . . . . . . . . . . . . . . 60

Structural Nonautoclavable Adhesive . . . . . . . . . . . . . . 850

Antichafe Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 660

Bearing Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620

Caulking and Smoothing Compounds . . . . . . . . . . . . . . . . 850

Chemical Agent-Resistant Coating . . . . . . . . . . . . . . . . . . 550

Clear Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720

Commercial Exterior Aerodynamic 

Structure Primer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650

Compatible Substrate Primer . . . . . . . . . . . . . . . . . . . . . . . 780

Corrosion Prevention Compound . . . . . . . . . . . . . . . . . . . 710

Cryogenic Flexible Primer . . . . . . . . . . . . . . . . . . . . . . . . 645

Cryoprotective Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . 600

Dry Lubricative Material . . . . . . . . . . . . . . . . . . . . . . . . . . 880

Electric or Radiation-Effect Coating . . . . . . . . . . . . . . . . . 800

Electrostatic Discharge and

Electromagnetic

Interference (EMI) Coating . . . . . . . . . . . . . . . . . . . . . . 800

Elevated-Temperature Skydrol-Resistant

Commercial Primer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 740

Epoxy Polyamide Topcoat . . . . . . . . . . . . . . . . . . . . . . . . 660

Fire-Resistant (interior) Coating . . . . . . . . . . . . . . . . . . . . 800

Flexible Primer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

Flight-Test Coatings:

Missile or Single Use Aircraft . . . . . . . . . . . . . . . . . . . . 420

All Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840

Fuel-Tank Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720

High-Temperature Coating . . . . . . . . . . . . . . . . . . . . . . . . 850

Insulation Covering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 740

Intermediate Release Coating . . . . . . . . . . . . . . . . . . . . . . 750

Lacquer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830

Maskants:

Bonding Maskant . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,230

Critical Use and Line Sealer Maskant . . . . . . . . . . . . . 1,020

Seal Coat Maskant . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,230

Metallized Epoxy Coating . . . . . . . . . . . . . . . . . . . . . . . . . 740

Mold Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780

Optical Anti-Reflective Coating . . . . . . . . . . . . . . . . . . . . 750

Part Marking Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850

Pretreatment Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780

Rain Erosion-Resistant Coating . . . . . . . . . . . . . . . . . . . . 850

Rocket Motor Nozzle Coating . . . . . . . . . . . . . . . . . . . . . . 660

Scale Inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880

Screen Print Ink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840

Sealants:

Extrudable/Rollable/Brushable Sealant . . . . . . . . . . . . 280

Sprayable Sealant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600

Silicone Insulation Material . . . . . . . . . . . . . . . . . . . . . . . 850

Solid Film Lubricant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880

Specialized Function Coating . . . . . . . . . . . . . . . . . . . . . . 890

Temporary Protective Coating . . . . . . . . . . . . . . . . . . . . . 320

Thermal Control Coating . . . . . . . . . . . . . . . . . . . . . . . . . . 800

Wet Fastener Installation Coating . . . . . . . . . . . . . . . . . . . 675

Wing Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850

a

Coating limits are expressed in terms of mass (grams) or VOC per volume (liter) of

coating less water and less exempt

 solvent.

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Exemptions. The following applications are exempt from the

presumptive RACT coating limits in Table 4-1:

1. Touchup, aerosol, and DOD classified coatings;

2. Coatings used on space vehicles; and

3. Facilities that use separate formulations in volumes of

less than 50 gallons per year, subject to a maximum exemption of

200 gallons for all such formulations applied annually.

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4.2 PRIMERS, TOPCOATS, CHEMICAL MILLING MASKANTS

The broad categories of primers, topcoats (including selfpriming topcoats), and chemical milling maskants (Type I/II) are

not specialty coatings as listed in Table 4-1 and are regulated

for major sources under the Aerospace NESHAP requiring MACT

limits with a compliance date specified in 40 CFR 63.749(a). 

These limits may be assumed to represent RACT limits 1 year after

the major sources are required to meet the MACT limits and,

therefore, shall not be effective until 1 year after the NESHAP

compliance date of September 1, 1998. The requirements do not

apply to facilities that use separate formulations of primers,

topcoats, and chemical milling maskants (Type I/II) in volumes of

less than 50 gallons per year, subject to a maximum exemption of

200 gallons total for such formulations applied annually.

4.3 APPLICATION EQUIPMENT FOR PRIMERS AND TOPCOATS

Presumptive RACT for primer and topcoat (including selfpriming topcoats) application equipment used on aerospace

components and vehicles is based on current practices and

requirements in some States. Except as provided in Section 4.3

and Subsection 4.3.1, the presumptive RACT for primer and topcoat

(including self-priming topcoat) application equipment is the use

of one or more of the following application techniques: flow/

curtain coat; dip coat; roll coating; brush coating; cottontipped swab application; electrodeposition coating; high volume

low pressure (HVLP) spraying; electrostatic spray; or other

coating application methods that achieve emission reductions

equivalent to HVLP or electrostatic spray application methods.

4.3.1 Exemptions

The following situations are exempt from the presumptive

RACT application techniques described in Section 4.3:

1. Any situation that normally requires the use of an

airbrush or an extension on the spray gun to properly reach

limited access spaces;

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2. The application of specialty coatings;

3. 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 Section 4.3;

4. 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 by

any of the application methods specified in Section 4.3;

5. The use of airbrush application methods for stenciling,

lettering, and other identification markings;

6. The use of hand-held spray can application methods; and

7. Touch-up and repair operations.

4.3.2 Timing (Schedule) of Compliance

The application techniques identified as presumptive RACT

are regulated for major sources under the Aerospace NESHAP

requiring MACT application equipment with a compliance date of

September 1, 1998 specified in 40 CFR 63.749(a). These equipment

requirements may be assumed to represent RACT requirements 1 year

after the major sources are required to meet the MACT equipment

requirements and, therefore, shall not be effective until 1 year

after the NESHAP compliance date of September 1, 1998.

4.4 CLEANING OPERATIONS

For solvent cleaning operations, this guidance departs from

the standard presumptive RACT requirement to incorporate MACT

level controls. Therefore, the requirements of Section 4.2 shall

not become effective prior to the Aerospace NESHAP compliance

date of September 1, 1998. The MACT and RACT for solvent

cleaning is based on work practices and cleaning solvent

composition. Except as provided in Section 4.0 and

Subsection 4.4.2, MACT and RACT for certain activities is

described below. 

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4.4.1 Housekeeping

All fresh and used cleaning solvents, except semiaqueous

cleaning solvents, used in solvent cleaning operations shall be

stored in containers that shall be kept closed at all times

except when filling or emptying. It is recommended that cloth

and paper, or other absorbent applicators, moistened with

cleaning solvents be stored in closed containers. Cotton-tipped

swabs used for very small cleaning operations are exempt. In

addition, the owner or operator must implement handling and

transfer procedures to minimize spills during filling and

transferring the cleaning solvent to or from enclosed systems,

vats, waste containers, and other cleaning operation equipment

that hold or store fresh or used cleaning solvents. The above

requirements are known collectively as housekeeping measures. 

Aqueous cleaning solvents are excluded from these housekeeping

requirements. 

4.4.2 Hand-Wipe Cleaning

Hand-wipe cleaning operations require the use of cleaning

solvents which are aqueous or have a VOC composite vapor pressure

less than or equal to 45 millimeters of mercury (mm Hg) at 20°C. 

Exemptions

The following cleaning operations would be exempt from the

cleaning solvent composition and vapor pressure requirements

stated in Section 4.4.2: 

 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, hydrazine); 

 3. Cleaning and surface activation prior to adhesive

bonding; 

 4. Cleaning of electronics and assemblies containing

electronics; 

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 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; 

 8. Cleaning during fabrication, assembly, installation,

and maintenance of upholstery, curtains, carpet, and other

textile materials used on 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, polycarbonates, or

glass substrates;

11. Cleaning and cleaning solvent usage associated with

research and development, quality control, or laboratory testing;

12. Cleaning operations, using nonflammable liquids,

conducted within 5 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. 

4.4.3 Flush Cleaning

For cleaning solvents used in the flush cleaning of

aerospace parts, assemblies, and coating unit components, the

used cleaning solvent (except for semiaqueous cleaning solvents)

must be emptied into an enclosed container or collection system

that is kept closed when not in use or captured on wipers and

disposed of in accordance with Section 4.4.1. Aqueous cleaning

solvents are excluded from these flush cleaning requirements. 

4.4.4 Spray Gun Cleaning

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All spray guns must be cleaned by one or more of the

following methods: 

1. Enclosed spray gun cleaning system that is kept closed

when not in use, provided that leaks from enclosed spray gun

cleaners are repaired within 14 days from when the leak is first

discovered. 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. Unatomized discharge of cleaning solvent into a waste

container that is kept closed when not in use;

3. Disassembled spray gun that is cleaned in a vat and kept

closed when not in use; or

4. Atomized spray into a waste container that is fitted

with a device designed to capture atomized cleaning solvent

emissions. 

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5.0 GUIDANCE TO STATE ENFORCEMENT AGENCIES

This chapter presents information for air quality management

agencies to consider in developing an enforceable rule limiting

VOC emissions from coating and solvent cleaning operations at

aerospace manufacturing and rework facilities. The State or

other implementing agency can exercise its prerogative to

consider other options provided that they meet the objectives

prescribed in this chapter.

This guidance is for instructional purposes only and, as

such, is not binding. In the development of a State or local

aerospace manufacturing and rework operations rule, the State or

other enforcement agency should consider all information

presented in the CTG and the promulgated NESHAP along with

additional information about specific sources to which the rule

will apply. The reasonably available control technology (RACT)

rule, however, should address all the factors listed in this

chapter and in Section 4 to ensure that the rule has reasonable

provisions for demonstrating compliance and is enforceable. A

model rule which contains all these requirements is provided in

Appendix B. The model rule is guidance only and the State or

local agency has the flexibility to adopt alternative measures,

including market-based incentive programs, provided they meet EPA

enforceability criteria. 

5.1 DEFINITIONS

The RACT rule should accurately describe the types of

sources that would be affected and clearly define terms used to

describe the industry or applicable control methods. Example

definitions of pertinent terms are presented in Appendix A for

reference by the State or local agency. 

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5.2 APPLICABILITY

The recommended RACT described in this document applies to

the manufacture of aerospace vehicles and components as well as

the rework or repair of these aerospace products. (See

Section 2.) This guidance has been developed for affected

sources in areas of moderate, serious, or severe nonattainment

that have the potential to emit greater than or equal to 25 tons

per year of VOC's. The guidance is intended to apply to affected

sources in extreme areas, however, if potential VOC emissions are

greater than or equal to 10 tons per year. The State or local

agency has the flexibility to apply RACT as deemed necessary. 

For example, an agency may apply RACT to all sources that have

actual emissions at 50 percent of these thresholds. 

5.3 COMPLIANCE, MONITORING, RECORDKEEPING & REPORTING PROVISIONS

The State or local agency is responsible for ensuring that

appropriate requirements for compliance determination (testing),

monitoring, recordkeeping and reporting are incorporated into its

RACT rule. These requirements must meet two objectives: (1) the

agency's need to demonstrate VOC emission reductions and

(2) EPA's criteria for enforceability. Because source types,

compliance methods, and agency requirements may vary

substantially across the nation, specific provisions for

compliance determination (testing), monitoring, recordkeeping and

reporting are not included in this CTG.

However, for a State's RACT rules to be enforceable, they

must definitively set forth recordkeeping, monitoring, and

compliance determination (testing) requirements appropriate to

the type of source(s) being regulated and sufficient to allow

determinations whether the source(s) are in compliance. 

Therefore, EPA's Model Rule, which accompanies this CTG, contains

suggested recordkeeping, testing, and monitoring provisions that

EPA believes are sufficient to enable EPA and the States to

determine compliance with the RACT requirements of the Model

Rule. The State or other implementing agency can exercise its

prerogative to consider various recordkeeping, testing, and

monitoring requirements provided they meet the objectives

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prescribed in this CTG. This guidance is for instructional

purposes only and, as such, is not binding.

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APPENDIX A. DEFINITIONS

Terms used in this CTG and the Model Rule in Appendix B are

defined in the Clean Air Act (Act), or in this section as

follows:

Ablative coating means 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 means a very thin coating applied to a

substrate to promote wetting and form a chemical bond with the

subsequently applied material.

Adhesive bonding primer means 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 means 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.

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.

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Aircraft transparency means the aircraft windshield, canopy,

passenger windows, lenses and other components which are

constructed of transparent materials.

Antichafe coating means a coating applied to areas of moving

aerospace components that may rub during normal operations or

installation.

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.

Aqueous cleaning solvent means a solvent in which water is

at least 80 percent of the solvent as applied.

Bearing coating means 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 means 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 means 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) means an exterior

topcoat designed to withstand exposure to chemical warfare agents

or the decontaminants used on these agents.

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 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,

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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

not included. Maskants that are defined as specialty coatings

are not included under this definition.

Cleaning operation means collectively spray-gun, hand-wipe,

and flush cleaning operations.

Cleaning solvent means a liquid material used for hand-wipe,

spray gun, or flush cleaning. This definition does not include

solutions that contain no VOC.

Clear coating means 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.

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 using a spray booth, tank, or other

enclosure or any area, such as a hangar, for applying a single

type of coating (e.g., primer); using the same spray booth for

applying 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 to be included in this

definition.

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Commercial exterior aerodynamic structure primer means 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 means materials used in the

bonding of passenger cabin interior components. These components

must meet the FAA fireworthiness requirements.

Compatible substrate primer means either compatible epoxy

primer or 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 epoxypolyamide 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. 

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.

Corrosion prevention system means a coating system that

provides corrosion protection by displacing water and penetrating

mating surfaces, forming a protective barrier between the metal

surface and moisture. Coatings containing oils or waxes are

excluded from this category.

Critical use and line sealer maskant means 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, or highAPPENDIX F: CTGSAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT June 16, 2011 F - 45 Final Draft Staff Report with Appendices 

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A-8

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 means 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 means a coating that insulates

cryogenic or subcooled surfaces to limit propellant boil-off,

maintain structural integrity of metallic structures during

ascent or re-entry, and prevent ice formation.

Cyanoacrylate adhesive means a fast-setting, single

component adhesive that cures at room temperature. Also known as

"super glue."

Dry lubricative material means a coating consisting of

lauric acid, cetyl alcohol, waxes, or other noncross linked or

resin-bound materials that act as a dry lubricant.

Electric or radiation-effect coating means 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 means 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

means 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

APPENDIX F: CTGSAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT June 16, 2011 F - 46 Final Draft Staff Report with Appendices 

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or equivalent) at the elevated temperature of 150°F for

1,000 hours.

Epoxy polyamide topcoat means a coating used where harder

films are required or in some areas where engraving is

accomplished in camouflage colors.

Exempt solvent means a specified organic compound that has

been determined by the EPA to have negligible photochemical

reactivity and is listed in 40 CFR 51.100. 

Fire-resistant (interior) coating means 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 that are subject to the flammability

requirements of MIL-STD-1630A and MIL-A-87721. For space

applications, these coatings are used on parts that are subject

to the flammability requirements of SE-R-0006 and SSP 30233.

Flexible primer means 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 means 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.

Flush cleaning means 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 assisted by air or

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

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where wiping, scrubbing, mopping, or other hand action are used

are not included.

Fuel tank adhesive means an adhesive used to bond components

exposed to fuel and must be compatible with fuel tank coatings.

Fuel tank coating means a coating applied to fuel tank

components for the purpose of corrosion and/or bacterial growth

inhibition and to assure sealant adhesion in extreme

environmental conditions.

Grams of VOC per liter of coating (less water and less

exempt solvent) means the weight of VOC per combined volume of

total volatiles and coating solids, less water and exempt

compounds, and can be calculated by the following equation:

Ws = weight of total volatiles in grams

Ww = weight of water in grams

Wes = weight of exempt compounds in grams

Vs = volume of coating in liters

Vw = volume of water in liters

Ves = volume of exempt compounds in liters 

Hand-wipe cleaning operation means removing contaminants

such as dirt, grease, oil, and coatings from an aerospace vehicle

or component by physically rubbing it with a material such as a

rag, paper, or cotton swab that has been moistened with a

cleaning solvent.

High temperature coating means a coating designed to

withstand temperatures of more than 350°F.

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.

Insulation covering means material that is applied to foam

insulation to protect the insulation from mechanical or

environmental damage.

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Intermediate release coating means 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 means 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.

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.

Metalized epoxy coating means a coating that contains

relatively large quantities of metallic pigmentation for

appearance and/or added protection.

Mold release means a coating applied to a mold surface to

prevent the molded piece from sticking to the mold as it is

removed.

Nonstructural adhesive means an adhesive that bonds nonload

bearing aerospace components in noncritical applications and is

not covered in any other specialty adhesive categories.

Operating parameter value means a minimum or maximum value

established for a control equipment or process parameter that, if

achieved by itself or in combination with one or more other

operating parameter values, determines that an owner or operator

has continued to comply with an applicable emission limitation.

Optical antireflection coating means a coating with a low

reflectance in the infrared and visible wavelength ranges that is

used for antireflection on or near optical and laser hardware.

Part marking coating means coatings or inks used to make

identifying markings on materials, components, and/or assemblies. 

These markings may be either permanent or temporary.

Pretreatment coating means an organic coating that contains

at least 0.5 percent acids by weight and is applied directly to

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metal or composite surfaces to provide surface etching, corrosion

resistance, adhesion, and ease of stripping.

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. Primers

that are defined as specialty coatings are not included under

this definition.

Radome means the nonmetallic protective housing for.

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

electronic countermeasures, etc.).

 Rain erosion-resistant coating means 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.

Research and development means an operation whose primary

purpose is for research and development of new processes and

products and that is conducted under the close supervision of

technically trained personnel and is not involved in the

manufacture of final or intermediate products for commercial

purposes, except in a de minimis manner.

Rocket motor bonding adhesive means an adhesive used in

rocket motor bonding applications.

Rocket motor nozzle coating means a catalyzed epoxy coating

system used in elevated temperature applications on rocket motor

nozzles.

Rubber-based adhesive means a quick setting contact cement

that provide a strong, yet flexible bond between two mating

surfaces that may be of dissimilar materials.

Scale inhibitor means a coating that is applied to the

surface of a part prior to thermal processing to inhibit the

formation of scale.

Screen print ink means an ink used in screen printing

processes during fabrication of decorative laminates and decals. 

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Sealant means 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.

Seal coat maskant means an overcoat applied over a maskant

to improve abrasion and chemical resistance during production

operations.

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.

Semiaqueous cleaning solvent means a solution in which water

is a primary ingredient (>60 percent of the solvent solution as

applied must be water). 

 Silicone insulation material means an 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."

Solids means the nonvolatile portion of the coating that

after drying makes up the dry film.

 Solid film lubricant means a very thin coating consisting

of a binder system containing as its chief pigment material one

or more of the following: molybdenum, graphite,

polytetrafluoroethylene (PTFE), or other solids that act as a dry

lubricant between faying (i.e., closely or tightly fitting)

surfaces.

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, that 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. 

Specialized function coating means a coating that fulfills

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.

Spray gun means a device that atomizes a coating or other

material and projects the particulates or other material onto a

substrate.

Structural autoclavable adhesive means an adhesive used to

bond load-carrying aerospace components that is cured by heat and

pressure in an autoclave.

Structural nonautoclavable adhesive means an adhesive cured

under ambient conditions that is used to bond load-carrying

aerospace components or other critical functions, such as

nonstructural bonding in the proximity of engines.

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.

Temporary protective coating means 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.

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Thermal control coating means a coating formulated with

specific thermal conductive or radiative properties to permit

temperature control of the substrate.

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

aerospace vehicle or component for appearance, identification,

camouflage, or protection. Topcoats that are defined as

specialty coatings are not included under this definition.

Touch-up and repair coating means a coating used to cover

minor coating imperfections appearing after the main coating

operation.

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.

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.

VOC composite vapor pressure means the sum of the partial

pressures of the compounds defined as VOC's and is determined by

the following calculation:

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

Ww = Weight of water, grams.

We = Weight of nonwater, non-VOC compound, grams.

MWi = Molecular weight of the "i"th VOC compound, g/g-mole.

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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.

Waterborne (water-reducible) coating means a coating which

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

volatile fraction.

Wet fastener installation coating means a primer or sealant

applied by dipping, brushing, or daubing to fasteners that are

installed before the coating is cured.

Wing coating means a corrosion-resistant topcoat that is

resilient enough to withstand the flexing of the wings. 

APPENDIX F: CTGSAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT June 16, 2011 F - 54 Final Draft Staff Report with Appendices 

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B-1

APPENDIX B. AEROSPACE MANUFACTURING AND REWORK

OPERATIONS MODEL RULE

B.1 APPLICABILITY

(a) Provisions of this Rule

(1) Except as noted in (a)(2) and (a)(3), this rule applies

to the manufacture or rework of commercial, civil, or military

aerospace vehicles or components at facilities located in severe,

serious, and moderate ozone nonattainment areas that have the

potential to emit 25 tons per year of VOC or more or are located

in extreme nonattainment areas and have potential to emit 10 tons

per year or more.

(2) This rule does not apply to the following activities

where cleaning and coating of aerospace components and vehicles

may take place: research and development, quality control,

laboratory testing, and electronic parts and assemblies (except

for cleaning and coating of completed assemblies). 

(3) This rule does not apply to manufacturing or rework

operations involving space vehicles or rework operations

performed on antique aerospace vehicles or components.

B.2 DEFINITIONS

For the purpose of this rule the definitions listed in

Appendix A shall apply.

B.3 REQUIREMENTS

(a) VOC content of coatings.

(1) A person shall not apply to aerospace vehicles or

components any specialty coatings, including any VOC-containing

materials added to the original coating supplied by the

manufacturer, that contain VOC in excess of the limits specified

below:

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VOC CONTENT LIMITS FOR SPECIALTY COATINGS (g/L)a

Coating type Limit Coating type Limit

Ablative Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600

Adhesion Promoter . . . . . . . . . . . . . . . . . . . . . . . . . . . 890

Adhesive Bonding Primers:

Cured at 250°F or below . . . . . . . . . . . . . . . . . . . . . 850

Cured above 250°F . . . . . . . . . . . . . . . . . . . . . . . . 1030

Adhesives:

Commercial Interior Adhesive . . . . . . . . . . . . . . . . 760

Cyanoacrylate Adhesive . . . . . . . . . . . . . . . . . . . . 1,020

Fuel Tank Adhesive . . . . . . . . . . . . . . . . . . . . . . . . 620

Nonstructural Adhesive . . . . . . . . . . . . . . . . . . . . . 360

Rocket Motor Bonding Adhesive . . . . . . . . . . . . . . 890

Rubber-based Adhesive . . . . . . . . . . . . . . . . . . . . . 850

Structural Autoclavable Adhesive . . . . . . . . . . . . . . 60

Structural Nonautoclavable Adhesive . . . . . . . . . . 850

Antichafe Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . 660

Bearing Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620

Caulking and Smoothing Compounds . . . . . . . . . . . . 850

Chemical Agent-Resistant Coating . . . . . . . . . . . . . . 550

Clear Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 720

Commercial Exterior Aerodynamic 

Structure Primer . . . . . . . . . . . . . . . . . . . . . . . . . . . 650

Compatible Substrate Primer . . . . . . . . . . . . . . . . . . . 780

Corrosion Prevention Compound . . . . . . . . . . . . . . . . 710

Cryogenic Flexible Primer . . . . . . . . . . . . . . . . . . . . . 645

Dry Lubricative Material . . . . . . . . . . . . . . . . . . . . . . 880

Cryoprotective Coating . . . . . . . . . . . . . . . . . . . . . . . 600

Electric or Radiation-Effect Coating . . . . . . . . . . . . . 800

Electrostatic Discharge and Electromagnetic

Interference (EMI) Coating . . . . . . . . . . . . . . . . . . 800

Elevated-Temperature Skydrol-Resistant

Commercial Primer . . . . . . . . . . . . . . . . . . . . . . . . 740

Epoxy Polyamide Topcoat . . . . . . . . . . . . . . . . . . . . . 660

Fire-Resistant (interior) Coating . . . . . . . . . . . . . . . . . 800

Flexible Primer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

Flight-Test Coatings:

Missile or Single Use Aircraft . . . . . . . . . . . . . . . . 420

All Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840

Fuel-Tank Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . 720

High-Temperature Coating . . . . . . . . . . . . . . . . . . . . . 850

Insulation Covering . . . . . . . . . . . . . . . . . . . . . . . . . . 740

Intermediate Release Coating . . . . . . . . . . . . . . . . . . . 750

Lacquer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830

Maskants:

Bonding Maskant . . . . . . . . . . . . . . . . . . . . . . . . . 1,230

Critical Use and Line Sealer Maskant . . . . . . . . . 1,020

Seal Coat Maskant . . . . . . . . . . . . . . . . . . . . . . . . 1,230

Metallized Epoxy Coating . . . . . . . . . . . . . . . . . . . . . 740

Mold Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 780

Optical Anti-Reflective Coating . . . . . . . . . . . . . . . . . 750

Part Marking Coating . . . . . . . . . . . . . . . . . . . . . . . . . 850

Pretreatment Coating . . . . . . . . . . . . . . . . . . . . . . . . . 780

Rain Erosion-Resistant Coating . . . . . . . . . . . . . . . . . 850

Rocket Motor Nozzle Coating . . . . . . . . . . . . . . . . . . 660

Scale Inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880

Screen Print Ink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840

Sealants:

Extrudable/Rollable/Brushable Sealant . . . . . . . . . 280

Sprayable Sealant . . . . . . . . . . . . . . . . . . . . . . . . . . 600

Silicone Insulation Material . . . . . . . . . . . . . . . . . . . . 850

Solid Film Lubricant . . . . . . . . . . . . . . . . . . . . . . . . . 880

Specialized Function Coating . . . . . . . . . . . . . . . . . . . 890

Temporary Protective Coating . . . . . . . . . . . . . . . . . . 320

Thermal Control Coating . . . . . . . . . . . . . . . . . . . . . . 800

Wet Fastener Installation Coating . . . . . . . . . . . . . . . 675

Wing Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850

a Coating limits expressed in terms of mass (grams) of VOC per volume (liters) of coating less water and less exempt

solvent.

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(2) The following coating applications are exempt from the

VOC content limits listed in paragraph (B.3)(a)(1):

(i) Touchup, aerosol, and DoD "classified" coatings

(ii) Coating of space vehicles

(iii) Facilities that use separate formulations in volumes

of less than 50 gallons per year subject to a maximum exemption

of 200 gallons total for such formulations applied annually.

(3) Primers, Topcoats, Chemical Milling Maskants. The

broad categories of primers, topcoats (including self-priming

topcoats), and chemical milling maskants (Type I/II) are not

specialty coatings as listed in the table in (B.3)(a)(1) and are

regulated for major sources under the Aerospace NESHAP requiring

MACT limits with a compliance date of September 1, 1998 as

specified in 40 CFR 63.749(a). These limits may be assumed to

represent RACT limits 1 year after the major sources are required

to meet the MACT limits and, therefore, shall not be effective

until 1 year after the NESHAP compliance date. The requirements

do not apply to facilities that use separate formulations of

primers, topcoats, and chemical milling maskants (Type I/II) in

volumes of less than 50 gallons per year, subject to a maximum

exemption of 200 gallons total for such formulations applied

annually.

(b) Application equipment.

(1) A person shall use one or more of the following

application techniques in applying any primer or topcoat to

aerospace vehicles or components: flow/curtain coat; dip coat;

roll coating; brush coating; cotton-tipped swab application;

electrodeposition coating; high volume low pressure (HVLP)

spraying; electrostatic spray; or other coating application

methods that achieve emission reductions equivalent to HVLP or

electrostatic spray application methods.

(2) The following situations are exempt from application

equipment requirements listed in paragraph (B.3)(b)(1):

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(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 specialty coatings;

(iii) 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 Section (B.3)(b)(1);

(iv) 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 by

any of the application methods specified in Section (B.3)(b)(1);

(v) The use of airbrush application methods for stenciling,

lettering, and other identification markings;

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

and

(vii) Touch-up and repair operations.

(3) The application techniques listed in

paragraph (B.3)(b)(1) are regulated for major sources under the

Aerospace NESHAP requiring MACT application equipment with a

compliance date of September 1, 1998 specified in 40 CFR

63.749(a). These equipment requirements may be assumed to

represent RACT requirements 1 year after the major sources are

required to meet the MACT equipment requirements and, therefore,

shall not be effective until 1 year after the NESHAP compliance

date of September 1, 1998.

(c) Solvent cleaning. The following requirements apply to

solvent cleaning operations and shall not be effective until the

Aerospace NESHAP compliance date of September 1, 1998: 

(1) Hand-wipe cleaning. Cleaning solvents used in handwipe cleaning operations shall:

(i) Meet the definition of aqueous cleaning solvent in

Appendix A, or 

(ii) Have a VOC composite vapor pressure less than or equal

to 45 millimeters of mercury (mm Hg) at 20°C.

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(2) The following solvent cleaning operations are exempt

from the requirements in paragraph (B.3)(c)(1):

(i) Cleaning during the manufacture, assembly,

installation, maintenance, or testing of components of breathing

oxygen systems that are exposed to the breathing oxygen;

(ii) 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, hydrazine);

(iii) Cleaning and surface activation prior to adhesive

bonding;

(iv) Cleaning of electronics parts and assemblies

containing electronics parts;

(v) 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;

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

spaces;

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

thermal control surfaces;

(viii) Cleaning during fabrication, assembly, installation,

and maintenance of upholstery, curtains, carpet, and other

textile materials used on the interior of the aircraft;

(ix) 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;

(x) Cleaning of aircraft transparencies, polycarbonate, or

glass substrates;

(xi) Cleaning and solvent usage associated with research

and development, quality control, or laboratory testing;

(xii) Cleaning operations, using nonflammable liquids,

conducted within 5 feet of energized electrical systems. 

Energized electrical systems means any AC or DC electrical

circuit on an assembled aircraft once electrical power is

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connected, including interior passenger and cargo areas, wheel

wells and tail sections; and,

(xiii) 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.

(3) Flush cleaning. For cleaning solvents used in the

flush cleaning of parts, assemblies, and coating unit components,

the used cleaning solvent (except for semiaqueous cleaning

solvents) must be emptied into an enclosed container or

collection system that is kept closed when not in use or captured

with wipers provided they comply with the housekeeping

requirements of (B.3)(c)(5). Aqueous cleaning solvents are

exempt from these requirements.

(4) Spray gun cleaning. All spray guns must be cleaned by

one or more of the following methods:

(i) Enclosed spray gun cleaning system provided that it is

kept closed when not in use and leaks are repaired within 14 days

from when the leak is first discovered. If the leak is not

repaired by the 15th day after detection, the solvent shall be

removed and the enclosed cleaner shall be shut down until the

leak is repaired or its use is permanently discontinued,

(ii) Unatomized discharge of solvent into a waste container

that is kept closed when not in use,

(iii) Disassembly of the spray gun and cleaning in a vat

that is kept closed when not in use, or,

(iv) Atomized spray into a waste container that is fitted

with a device designed to capture atomized solvent emissions.

(5) Housekeeping. All fresh and used cleaning solvents,

except semiaqueous cleaning solvents, used in solvent cleaning

operations shall be stored in containers that shall be kept

closed at all times except when filling or emptying. It is

recommended that cloth and paper, or other absorbent applicators,

moistened with cleaning solvents be stored in closed containers. 

Cotton-tipped swabs used for very small cleaning operations are

exempt. In addition, the owner or operator must implement

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handling and transfer procedures to minimize spills during

filling and transferring the cleaning solvent to or from enclosed

systems, vats, waste containers, and other cleaning operation

equipment that hold or store fresh or used cleaning solvents. 

The above requirements are known collectively as housekeeping

measures. Aqueous cleaning solvents are exempt from these

requirements. 

(d) Control equipment and monitoring. 

(1) Each owner or operator may comply with the provisions

of paragraph (B.3)(a) by using approved air pollution control

equipment provided that the control system has combined VOC

emissions capture and control equipment efficiency of at least

81 percent by weight.

(2) Each owner or operator shall submit a monitoring plan

that specifies the applicable operating parameter value, or range

of values, to ensure ongoing compliance with (B.3)(d)(1). The

monitoring device shall be installed, calibrated, operated, and

maintained in accordance with the manufacturer's specifications. 

(3) Each owner or operator using an enclosed spray gun

cleaner shall visually inspect the seals and all other potential

sources of leaks at least once per month. Each inspection shall

occur while the spray gun cleaner is in operation. 

B.4 RECORDKEEPING REQUIREMENTS

(a) Each owner or operator using coatings listed in

(B.3)(a) shall:

(1) Maintain a current list of coatings in use with

category and VOC content as applied.

(2) Record coating usage on an annual basis

(b) Each owner or operator using cleaning solvents required

in (B.3)(c) shall:

(1) For aqueous and semiaqueous hand-wipe cleaning

solvents, maintain a list of materials used with corresponding

water contents.

(2) For vapor pressure compliant hand-wipe cleaning

solvents:

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(i) Maintain a current list of cleaning solvents in use

with their respective vapor pressures or, for blended solvents,

VOC composite vapor pressures.

(ii) Record cleaning solvent usage on an annual basis.

(3) For cleaning solvents with a vapor pressure greater

than 45 mm Hg used in exempt hand-wipe cleaning operations:

(i) Maintain a list of exempt hand-wipe cleaning processes.

(ii) Record cleaning solvent usage on an annual basis.

(c) Each owner or operator using control equipment under

paragraph (B.3)(d) shall record monitoring parameters as

specified in the monitoring plan required under (B.3)(d)(2).

(d) Except for Specialty Coatings, any source that complies

with the recordkeeping requirements of the Aerospace NESHAP,

40 CFR 63.752, is deemed to be in compliance with the

requirements of this paragraph (B.4). 

B.5 TEST METHODS

(a) For coatings which are not waterborne (waterreducible), determine the VOC content of each formulation (less

water and less exempt solvents) as applied using manufacturer's

supplied data or Method 24 of 40 CFR part 60, Appendix A. 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. For waterborne (water-reducible) coatings, manufacturer's supplied data

alone can be used to determine the VOC content of each

formulation.

(b) Cleaning solvents.

(1) For aqueous and semiaqueous cleaning solvents

manufacturers' supplied data shall be used to determine the water

content.

(2) For hand-wipe cleaning solvents required in

paragraph (B.3)(c)(1), manufacturers' supplied data or standard

engineering reference texts or other equivalent methods shall be

used to determine the vapor pressure or VOC composite vapor

pressure for blended cleaning solvents.

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(c) Control equipment. Measurements of VOC emissions

subject to paragraph (B.3)(d) shall be conducted in accordance

with EPA Methods 18, 25, and/or 25A (40 CFR 60, Appendix A).

(d) Except for Specialty Coatings, any source which

complies with the test method requirements of the Aerospace

NESHAP, 40 CFR 63.750, is deemed to be in compliance with the

requirements of this paragraph (B.5).

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