SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT 

APPENDIX E: CTG August 18, 2011 

Final Staff Report with Appendices 

 For Proposed Amendments to Rule 4684

E-1

APPENDIX E 

 EPA Control Technique Guidelines 

For Fiberglass Boating Manufacturing Materials 

August 18, 2011 
SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT 

APPENDIX E: CTG August 18, 2011 

Final Staff Report with Appendices 

 For Proposed Amendments to Rule 4684

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Control Techniques Guidelines for 

Fiberglass Boat Manufacturing Materials 

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EPA-453/R-08-004 

September 2008 

 

Control Techniques Guidelines for 

Fiberglass Boat Manufacturing Materials 

U.S. Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Sector Policies and Programs Division 

Research Triangle Park, NC 

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TABLE OF CONTENTS 

I. Introduction ................................................................................................................ 1 

II. Background and Overview ....................................................................................... 2 

III. Applicability................................................................................................................ 3 

IV. Process Description and Sources of VOC Emissions.............................................. 5 

A. Process Description ......................................................................................................... 5 

B. Sources of VOC Emissions ............................................................................................. 7 

V. Available Controls and Existing Federal, State, and Local ..................................... 

 Recommendations/Regulations ................................................................................ 8 

A. Available Control Options for Resin and Gel Coat ......................................................... 8 

1. Low VOC Resins and Gel Coats ............................................................................. 8 

2. Vapor Suppressed Resins and Gel Coats................................................................. 9 

3. Non-atomizing Resin Application ......................................................................... 10 

4. Closed Molding...................................................................................................... 11 

5. Add-On Control Systems....................................................................................... 14 

B. Available Control Options for Mixing Containers ......................................................... 14 

C. Available Control Options for Cleaning Materials......................................................... 14 

D. Existing Federal, State, and Local Recommendations/Regulations............................... 15 

1. The 1990 National VOC Assessment .................................................................... 15 

2. The 2001 NESHAP for Boat Manufacturing......................................................... 15 

3. Existing State and Local VOC Requirements ....................................................... 17 

VI. Recommended Control Options ................................................................................... 21 

A. Recommended VOC Limits for Gel Coats and Resins .............................................. 21 

1. Compliant Materials Option ................................................................................. 23 

2. Emissions Averaging Option ................................................................................. 24 

3. Add-on Control Option.......................................................................................... 27 

B. Recommended Option for Filled Resins..................................................................... 28 

C. Work Practices for Resin and Gel Coat Mixing Containers....................................... 28 

D. VOC Content and Vapor Pressure Limits for Cleaning Materials ............................. 29 

VII. Cost Effectiveness of Recommended Control Options.............................................. 29 

VIII. References .................................................................................................................... 31 

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I. Introduction

Clean Air Act (CAA) section 172(c)(1) provides that state implementation plans 

(SIPs) for nonattainment areas must include “reasonably available control measures” 

(RACM), including “reasonably available control technology” (RACT), for sources of 

emissions. Section 182(b)(2)(A) provides that for certain nonattainment areas, States 

must revise their SIPs to include RACT for each category of volatile organic compound 

(VOC) sources covered by a control techniques guidelines (CTG) document issued 

between November 15, 1990 and the date of attainment. 

The United States Environmental Protection Agency (EPA) defines 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.” 44 FR 53761 (September 17, 1979). In subsequent Federal 

Register notices, EPA has addressed how States can meet the RACT requirements of the 

Act. 

CAA section 183(e) directs EPA to list for regulation those categories of products 

that account for at least 80 percent of the volatile organic compound (VOC) emissions, 

on a reactivity-adjusted basis, from consumer and commercial products in areas that 

violate the NAAQS for ozone (i.e., ozone nonattainment areas). EPA issued the list on 

March 23, 1995, and has revised the list periodically. See 60 FR 15264 (March 23, 1995); 

see also 71 FR 28320 (May 16, 2006), 70 FR 69759 (Nov. 17, 2005); 64 FR 13422 

(March 18, 1999). Fiberglass boat manufacturing is included on the current section 

183(e) list. 

This CTG is intended to provide State and local air pollution control authorities 

information that should assist them in determining RACT for VOC from fiberglass boat 

manufacturing operations. In developing this CTG, EPA evaluated the sources of VOC 

emissions from the fiberglass boat manufacturing industry and the available control 

approaches for addressing these emissions, including the costs of such approaches. Based 

on available information and data, EPA provides recommendations for RACT for 

fiberglass boat manufacturing. 

States can use the recommendations in this CTG to inform their own 

determination as to what constitutes RACT for VOC for fiberglass boat manufacturing in 

their particular nonattainment areas. The information contained in this document is 

provided only as guidance. This guidance does not change, or substitute for, requirements 

specified in applicable sections of the CAA or EPA’s regulations; nor is it a regulation 

itself. This document does not impose any legally binding requirements on any entity. It 

provides only recommendations for State and local air pollution control agencies to 

consider in determining RACT. State and local pollution control agencies are free to 

implement other technically-sound approaches that are consistent with the CAA and 

EPA’s implementing regulations. 

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The recommendations contained in this CTG are based on data and information 

currently available to EPA. These general recommendations may not apply to a particular 

situation based upon the circumstances of a specific source. Regardless of whether a State 

chooses to implement the recommendations contained herein through State rules, or to 

issue State rules that adopt different approaches for RACT for VOC from fiberglass boat 

manufacturing operations, States must submit their RACT rules to EPA for review and 

approval as part of the SIP process. EPA will evaluate the rules and determine, through 

notice and comment rulemaking in the SIP approval process, whether the submitted rules 

meet the RACT requirements of the CAA and EPA’s regulations. To the extent a State 

adopts any of the recommendations in this guidance into its State RACT rules, interested 

parties can raise questions and objections about the substance of this guidance and the 

appropriateness of the application of this guidance to a particular situation during the 

development of the State rules and EPA’s SIP approval process. 

CAA section 182(b)(2) requires that a CTG issued after November 15, 1990 and 

the date of attainment include the date by which States subject to section 182(b) must 

submit SIP revisions in response to the CTG. Accordingly, EPA is providing in this CTG 

a one year period for the required submittal of a revised SIP. Pursuant to section 

182(b)(2), States required to submit rules consistent with section 182(b) must submit 

their SIP revisions within one year of the date of issuance of the final CTG for fiberglass 

boat manufacturing. 

II. Background and Overview

The EPA has not published a previous CTG for fiberglass boat manufacturing 

materials, but did publish an assessment of VOC emissions from fiberglass boat 

manufacturing in 1990. The 1990 assessment defined the nature and scope of VOC 

emissions from fiberglass boat manufacturing, characterized the industry, estimated per 

plant and national VOC emissions, and identified and evaluated potential control options. 

In 2001, EPA promulgated the National Emission Standards for Hazardous Air 

Pollutants for Boat Manufacturing, 40 CFR part 63, subpart VVVV (2001 NESHAP). 

The 2001 NESHAP established organic hazardous air pollutant (HAP) emissions limits 

based on low-HAP resins and gel coats and low-emitting resin application technology. 

Several of the air pollution control districts in California have specific regulations 

that control VOC emissions from fiberglass boat manufacturing operations, as part of 

their regulations for limiting VOC emissions from polyester resin operations. Several 

other states also have regulations that address VOC emissions from fiberglass boat 

manufacturing as part of polyester resin operations. A discussion of the applicability and 

control options found in the Federal actions, the California air district and other State 

rules is presented in Section V of this document. 

EPA developed the recommended approaches contained in this document after 

reviewing the 1990 VOC assessment, the 2001 NESHAP, and existing California district 

and other State VOC emission reduction approaches, and after considering information 

obtained since the issuance of the 2001 NESHAP. 

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The remainder of this document is divided into six sections. Section III describes 

the scope of sources to which the control recommendations in this CTG could apply. 

Section IV describes the fiberglass boat manufacturing processes and identifies the 

sources of VOC emissions from those processes. Section V describes the available 

control approaches for addressing VOC emissions from this product category and 

summarizes Federal, State and local approaches for addressing such emissions. Section 

VI provides our recommendations for RACT for fiberglass boat manufacturing materials. 

Section VII discusses the cost-effectiveness of the recommended control approaches. 

Section VIII contains a list of references.

III. Applicability

This CTG provides control recommendations for reducing VOC emissions from 

the use of gel coats, resins, and materials used to clean application equipment in 

fiberglass boat manufacturing operations. This section addresses EPA's recommendations 

as to the scope of entities to which the RACT recommendations in this CTG should 

apply. As explained above, this document is a guidance document and provides 

information for States to consider in determining RACT. When State and local pollution 

control agencies develop RACT rules, they may elect to adopt control approaches that 

differ from those described in this document and/or promulgate applicability criteria that 

differ from those recommended here. 

This CTG applies to facilities that manufacture hulls or decks of boats from 

fiberglass, or build molds to make fiberglass boat hulls or decks (hereinafter referred to 

as “fiberglass boat manufacturing facilities”). We do not extend our recommendations in 

this CTG to facilities that manufacture solely parts of boats (such as hatches, seats, or 

lockers), or boat trailers, but do not manufacture hulls or decks of boats from fiberglass, 

or build molds to make fiberglass boat hulls or decks. If a facility manufactures hulls or 

decks, or molds for hulls or decks, then the manufacture of all other fiberglass boat parts, 

including small parts such as hatches, seats, and lockers is also covered. 

We recommend that the control approaches discussed in Section VI of this CTG 

apply to each fiberglass boat manufacturing facility where the total actual VOC emissions 

from all fiberglass boat manufacturing operations covered by the recommendations in 

Section VI of this CTG are equal to or exceed 6.8 kg/day (15 lb/day). An alternative 

equivalent threshold would be 2.7 tons per 12-month rolling period. Cleaning materials 

should be included in determining whether total actual VOC emissions exceed this level. 

If a facility has add-on controls, then emissions before the add-on controls should be used 

in determining if a facility meets this threshold. 

The control approaches discussed in Section VI of this CTG do not extend to 

surface coatings applied to fiberglass boats, and do not apply to industrial adhesives used 

in the assembly of fiberglass boats. Surface coatings for fiberglass and metal recreational 

boats (pleasure craft) are addressed in the CTG for miscellaneous metal parts and plastic 

parts surface coating. Industrial adhesives used in boat assembly are addressed in the 

CTG for miscellaneous industrial adhesives. Polyester resin putties used to assemble 

fiberglass parts, however, are not considered adhesives and are addressed in this CTG. 

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We do not recommend the control approaches discussed in this CTG for facilities 

that emit below 6.8 kg/day because of the very small VOC emission reductions that could 

be achieved. Such a level is considered to be very low within the fiberglass boat 

manufacturing industry and is expected only from facilities producing only small 

numbers of small boats (such as specialty kayaks or canoes). Furthermore, based on the 

2002 National Emission Inventory (NEI) and the 2004 ozone nonattainment designations, 

we estimated that most of the fiberglass boat manufacturing facilities located in ozone 

nonattainment areas (67 out of 91 facilities) emit at or above this level. Therefore, these 

facilities would be addressed by our recommendations in the CTG. As mentioned above, 

for purposes of determining whether a facility meets our recommended applicability 

threshold, aggregate emissions, before consideration of control, from all fiberglass boat 

manufacturing operations (including related cleaning activities) at a given facility are 

included. 

In developing their RACT rules, State and local agencies should consider 

carefully the facts and circumstances of the affected sources in their States. As noted 

above, States can adopt the above recommended 15 lb/day actual VOC emissions or an 

equivalent applicability threshold, or they can develop other applicability criteria that 

they determine are appropriate, considering the facts and circumstances of the sources in 

their particular nonattainment areas. EPA will review the State RACT rules in the context 

of the SIP revision process.

Two items were used as sources of emissions data and statistical information 

concerning the fiberglass boat manufacturing industry as a whole. These were the 2002 

National Emission Inventory (NEI) and industry survey data collected by EPA during the 

development of the 2001 NESHAP. The NESHAP data provided by industry represented 

operations in 1996 and 1997. 

The NESHAP data indicate that styrene and methyl methacrylate (MMA), 

which are both VOC and organic HAP, account for nearly all the VOC emissions, as 

well as HAP emissions, from fiberglass boat manufacturing facilities. Therefore, total 

HAP and VOC emissions from fiberglass boat manufacturing facilities are nearly equal. 

The 2001 NESHAP estimated that baseline HAP emissions from boat manufacturing 

were 9,920 tons per year (tpy)a

, and we can assume that this estimate represents nearly 

all the VOC emissions as well. 

In developing this CTG, the 2002 NEI database was queried for VOC emissions 

generated by facilities that were listed under SIC 3732, boat building and repairing. This 

query resulted in 223 facilities with total VOC emissions of 9,100 tpy. In the Federal 

Register notice of November 17, 2005 regarding the changes to the Section 183(e) 

category list and schedule for regulation, EPA reported that VOC emissions from 

fiberglass boat manufacturing materials, based on the 1995 NEI, were 11,000 Mg/yr 

(12,100 tpy).b

 The general agreement among the 2002 NEI VOC emissions, the 2001 

NESHAP HAP emissions, and the 1995 NEI VOC emissions estimates, taking into 

 

a

 66 FR 44,222. August 22, 2001. 

b

 70 FR 69,760. November 17, 2005. 

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account possible changes in the industry over time, indicates that the query of the 2002 

NEI provides a reliable estimate of the number of facilities and total VOC emissions 

from fiberglass boat manufacturing materials.

IV. Process Description and Sources of VOC Emissions

Several types of boats are manufactured in the United States, including sailboats, 

powerboats, yachts, personal watercraft, and small miscellaneous boats such as kayaks 

and canoes. These boats are manufactured from a variety of materials, including, but not 

limited to, fiberglass (also known as fiber reinforced plastic or FRP), aluminum, 

rotationally molded (rotomolded) polyethylene, and wood. Fiberglass is the most 

common material used in boat manufacturing and is the focus of this CTG. 

A. Process Description

 Boats made from fiberglass are typically manufactured in a process known as 

open molding. Separate molds are typically used for the boat hull, deck, and 

miscellaneous small FRP parts such as fuel tanks, seats, storage lockers, and hatches. The 

parts are built on or inside the molds using glass roving, cloth, or matc

 that is saturated 

with a thermosetting liquid resin such as unsaturated polyester or vinylester resin. The 

liquid resin is mixed with a catalyst before it is applied to the glass, which causes a crosslinking reaction between the resin molecules. The catalyzed resin hardens to form a rigid 

shape consisting of the plastic resin reinforced with glass fibers. 

 The fiberglass boat manufacturing process generally follows these production 

steps: 

 1) Before each use, the molds are cleaned and polished and then treated with a 

mold release agent that prevents the part from sticking to the mold. 

 2) The open mold is first spray-coated with a clear or pigmented polyester resin 

known as a gel coat. The gel coat will become the outer surface of the finished part. The 

gel coat is mixed with a catalyst as it is applied so that it will harden. The catalyst can be 

mixed either inside the spray gun (internal mix) or immediately after leaving separate 

orifices on the spray gun (external mix). The gel coat is applied to a thickness of about 18 

mils (0.018 inches). Clear gel coats are often mixed with metal flakes to create an 

automotive-type metallic finish over a pigmented gel coat. Pigmented gel coats are used 

when a solid color surface is desired. Most gel coats are pigmented. Since they do not 

have any pigments, clear gel coats usually have a higher VOC content than pigmented gel 

coats. 

 

c

 Roving is a bundle of continuous glass fibers that is fed from a spool to a specialized gun that chops the 

roving into short fibers, mixes them with catalyzed resin, and deposits them on the mold surface in a 

random pattern. Cloth is a fabric made of woven yarns of glass fibers. Mat is a prepared material 

consisting of short glass fibers that are fixed to each other in a random pattern by a chemical binder, or are 

mechanically stitched to a lightweight fabric. 

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 3) After the gel coat has hardened, the inside of the gel coat is coated with a skin 

coat of polyester resin and short glass fibers (either glass mat or chopped roving) and 

then rolled with a metal or plastic roller to compact the fibers and remove air bubbles. 

The skin coat is about 90 mils (0.09 inches) thick and is intended to prevent distortion of 

the gel coat (known as "print through") from the subsequent layers of fiberglass and 

resin; 

 4) After the skin coat has hardened, additional glass reinforcement in the form of 

chopped roving, chopped strand mat, or cloth is applied to the inside of the mold and 

saturated with catalyzed polyester resin. The resin is usually applied with either 

mechanical equipment or by hand using a bucket and brush or paint-type roller. 

 5) The saturated fabric is then rolled with a metal or plastic roller to compact the 

fibers and remove air bubbles. 

 6) More layers or “laminations” of woven glass or glass mat and resin are applied 

until the part is the desired thickness. The part is then allowed to harden while still in the 

mold. As the part cures it generates heat from the exothermic reactions that take place as 

the resin hardens; very thick parts may be built in stages to allow this heat to dissipate to 

prevent heat damage to the mold or part. 

 7) After the resin has cured, the part is removed from the mold and the edges are 

trimmed to the final dimensions. 

 8) The different FRP parts of the boat are assembled using small pieces of woven 

glass or glass mat and resin, adhesives, or mechanical fasteners. Polyester resin mixed 

with fillers to create putty is also often used to assemble fiberglass parts and to fill gaps 

between parts. The putty becomes part of the composite structure. The putties may be 

applied by hand, or by using mechanically powered equipment similar to a large caulking 

gun. 

 9) The interior surfaces of the boat may be coated, either by spray or brush, with 

pigmented gel coat that serves as a surface finish so the interior spaces have a uniform 

color. 

 10) Flotation foam is typically injected into closed cavities in the hulls of smaller 

boats to make the boat unsinkable and capable of floating upright if swamped. 

 11) After the assembly of the hull is complete, the electrical and mechanical 

systems and the engine are installed along with carpeting, seat cushions, and other 

furnishings, and the boat is prepared for shipment. 

 12) Some manufacturers paint the topsides of their boats to obtain a superior 

finish or the bottoms to prevent marine growth. However, this is not a common practice. 

 13) Larger boats generally also require extensive interior woodwork and cabin 

furnishings to be installed. 

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 As mentioned above, fiberglass boat manufacturing facilities covered by this CTG 

include facilities that construct the molds or “tools” that are used to build the separate 

parts of the fiberglass boat. Most fiberglass boat manufacturers also build their own 

molds, although some obtain molds from facilities dedicated to building molds, either at a 

separate facility within a larger company, or as a completely separate entity. The 

production of molds is done using specialized resins and gel coats referred to as tooling 

resin and gel coat. These differ from production resin and gel coat in that they are harder, 

more heat resistant, and more dimensionally stable than production materials. 

 Construction of a mold begins with the construction of a full-size model of the 

part to be manufactured. This model is often called a “plug” and the mold is eventually 

built over the finished plug. The plug is built from rigid foam that is carved to shape. 

The foam is then covered with tooling resin and fiberglass and then a layer of tooling gel 

coat, and then sanded to its final shape and then polished and waxed so the mold will not 

stick to it when the mold is finished. 

 The mold is then built over the plug using tooling gel coat and resin and 

fiberglass. The tooling gel coat will become the interior surface of the mold, supported 

by the resin and fiberglass. The tooling resin often has inert filler added to it so it is more 

dimensionally stable and is able to absorb more heat from the part during the molding 

process. A metal framework is also added to the exterior of the mold to support the mold 

after it is removed from the plug. When the mold is removed from the plug, the mold 

will have a cavity or exterior surface that is the exact opposite of the shape of the plug 

and parts that will produced. The interior surface of the mold is polished and waxed so 

that finished parts will not stick the mold surface and they can be removed. 

 A single mold can be used to make many copies of the same part. Occasionally a 

mold may need to be repaired if the surface is damaged during part removal. These 

repairs are done using tooling resin and gel coat to which extra styrene has been added so 

the repair material will bond to the existing mold surfaces. 

B. Sources of VOC Emissions

 Styrene and methyl methacrylate (MMA) are the primary VOC emitted from 

fiberglass boat manufacturing materials. The resins contain styrene and the gel coats 

contain both compounds. Styrene and MMA are monomers. A monomer is a volatile 

organic compound that partially combines with itself, or other similar compounds, by a 

cross-linking reaction to become a part of the cured resin. A fraction of each monomer 

compound evaporates during resin and gel coat application and curing. Not all of the 

styrene and MMA evaporate, because a majority of these compounds are bound in the 

cross-linking reaction between polymer molecules in the hardened resin or gel coat and 

become part of the finished product. In closed molding operations, nearly all of the 

monomers are bound in the cross-link reactions and emissions are very low. In the 

remainder of this CTG, these monomers in resins and gel coats are referred to as 

monomer VOC. Styrene and MMA are the only monomer VOC we have identified in the 

resins and gel coats used in fiberglass boat manufacturing. 

 

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 The fraction of monomer VOC that is emitted from resin and gel coat used for 

fiberglass boat manufacturing is dependent on several factors, including the initial 

monomer VOC content of the material, the application method, and the thickness of the 

part or layer that is curing. Monomer VOC emission rates are usually expressed in terms 

of lb monomer VOC emitted per ton of material applied (lb/ton), or kilogram per 

megagram (kg/Mg). Monomer VOC evaporation from gel coats is higher than from 

resins because gel coats are applied in thinner coats, which increases evaporation. When 

material is applied in thicker layers, the overlying material impedes evaporation from the 

underlying material, so a higher fraction is bound up during the cross linking reactions 

before it has a chance to evaporate. 

 Higher monomer VOC materials also tend to emit a higher fraction of the 

monomer VOC than lower monomer VOC materials. Therefore, lowering the monomer 

VOC content of the resin or gel coat has a two-fold effect: first, it decreases the amount 

of monomer VOC that could be emitted, and second, a smaller fraction of the monomer 

VOC that is present is emitted to the atmosphere. 

 The type of application equipment used also affects the fraction of monomer VOC 

that is emitted. Spray application equipment that atomizes the resin as it is applied 

creates small droplets with a high surface-to-volume ratio that increases the amount of 

monomer VOC that evaporates during application. Non-atomizing application methods 

minimize the surface area during application and reduce monomer VOC emission rates. 

These non-atomizing methods include resin flow coaters, which create consolidated 

streams of resin (like a shower head) instead of atomized droplets, pressure fed resin 

rollers that apply resin directly onto the part, and fluid impingement technology which 

creates large droplets. 

 Resins and gel coats may also contain non-monomer VOC that are not reactive 

and do not become part of the hardened resin or gel coat. All of the non-monomer VOC, 

if present, is assumed to be emitted. However, the non-monomer VOC constitute less 

than 5 percent of the total VOC in all resins and gel coats and usually comprise less than 

1 percent of each resin or gel coat, by weight. Many resins and gel coats do not contain 

reportable amounts of non-monomer VOC, based on a review of material safety data 

sheets (MSDS) for resins and gel coats. 

 Resin and gel coat application equipment requires solvent cleaning to remove 

uncured resin or gel coat after each use. The solvents used to clean the application 

equipment are also a potential source of VOC emissions.d

 Catalyzed resin or gel coat 

 

d

In a Federal Register notice, EPA stated that the cleaning operations associated with certain specified 

section 183(e) consumer and commercial product categories, including fiberglass boat manufacturing, 

would not be covered by EPA’s 2006 CTG for industrial cleaning solvents (71 FR 44522 and 44540, 

August 4, 2006). In the notice, EPA expressed its intention to address cleaning operations associated with 

these categories in the CTGs for these specified categories if the Agency determines that a CTG is 

appropriate for the respective categories. Accordingly, this draft CTG addresses VOC emissions from 

cleaning operations associated with fiberglass boat manufacturing. 

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will harden in the transfer hoses or application equipment if not flushed with a solvent 

after each use. 

V. Available Controls and Existing Federal, State, and Local 

 Recommendations/Regulations

 As previously mentioned, there are two main sources of VOC emissions from 

fiberglass boat manufacturing materials: (1) evaporation of VOC (i.e., both monomer and 

non-monomer VOC) from the gel coats and resins; and (2) evaporation of VOC from the 

cleaning materials. This section summarizes the available control options for reducing 

these VOC emissions and existing federal, State, and local VOC recommendations or 

requirements that address these emissions. 

A. Available Control Options for Resin and Gel Coat

 As mentioned above, all of the non-monomer VOC in the resins and gel coat 

materials, if present, is assumed to be emitted. We are not aware of any control measure 

currently being implemented to reduce non-monomer VOC emissions from resins and gel 

coats used in fiberglass boat manufacturing. However, there are available options for 

controlling monomer VOC emission from these materials. These control options for 

monomer VOC emissions are described below. 

1. Low monomer VOC Resins and Gel Coats 

 Reducing monomer VOC emissions from resins and gel coats used in open 

molding at fiberglass boat manufacturing facilities is achieved primarily by reducing the 

monomer VOC content of the materials (resin and gel coat) and by switching to nonatomizing resin application methods. 

 Industry and EPA-sponsored testing has experimentally measured the amount of 

VOC that is emitted, and formulae were developed to predict the VOC emission rates (lb 

VOC/ton of material applied) for different materials and application methods.e

 The resin 

and gel coat that were used in testing contained only monomer VOC (i.e., styrene and 

MMA); they did not contain non-monomer VOC. 

The different resins and gel coats can be reformulated to achieve varying levels of 

lowered monomer VOC contents, depending of their use in boat manufacturing. Because 

reducing the monomer VOC content reduces emissions by two interacting mechanisms 

(reducing the amount of monomer VOC available to be emitted and by reducing the 

fraction of monomer VOC that is emitted), monomer VOC emission reduction is not 

linearly related to monomer VOC content. For example, reformulating a resin from 40 

 

e

 This testing was done in conjunction with the development of the NESHAP for boat manufacturing (40 

CFR 63, subpart VVVV) and the NESHAP for reinforced plastic composite manufacturing (40 CFR 63, 

subpart WWWW). The formulae that were developed were incorporated into both of these final NESHAP. 

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percent monomer VOC, by weight, to 35 percent monomer VOC, achieves a 28 percent 

VOC emission reduction if the resin is applied with atomizing spray methods. 

With low-monomer VOC resins and gel coats, facility operators can achieve 

emission reductions without changes in equipment or work practices. Low-monomer 

VOC materials can also be combined with other emission reduction techniques, such as 

non-atomizing resin application, for additional emission reductions. For regulatory 

agencies, a low-monomer VOC material requirement is easy to monitor and enforce; it is 

also relatively easy for a facility to demonstrate compliance on a continuous basis. 

2. Vapor Suppressed Resins and Gel Coats 

 Vapor suppressed resins and gel coats can be used to reduce monomer VOC 

emissions, but they can present manufacturing problems when used for boat 

manufacturing. Vapor suppressed resins and gel coats have an additive, typically a wax, 

to reduce monomer VOC evaporation by forming a film on the surface of the resin or gel 

coat as it cures. Monomer VOC reductions of up to 40 percent have been measured for 

atomizing spray-applied vapor suppressed resin compared to conventional resins; no data 

are available for vapor-suppressed gel coats. Vapor suppressed resins and gel coats can 

be used to achieve emission reductions without changes in equipment. Vapor suppressed 

resins can also be combined with other emission reduction techniques, such as nonatomized resin application, for additional emission reductions. 

 However, adding a vapor-suppressing wax to a resin or gel coat may present 

significant technical problems in boat manufacturing. Because boats are relatively large 

and complex structures, they are usually built and assembled from subassemblies that 

must be bonded together. In order to achieve good secondary bondsf

 between parts made 

with vapor suppressed resins, the wax film on the bonding surfaces must be removed, 

usually by sanding or grinding, before the parts can be bonded. This additional surface 

preparation can be labor intensive; one California manufacturer estimates that switching 

to vapor-suppressed resins caused a 25-percent labor increase in building parts. More 

importantly, the ultimate strength of those secondary bonds may also be reduced, 

increasing the possibility of structural failure among assembled parts. 

 Vapor suppressed gel coat can be used only in limited applications because the 

wax will also prevent bonding with the gel coat. Since gel coats are applied in a thin 

layer, the wax cannot be removed to allow bonding with additional layers of material. 

Therefore, vapor suppressed gel coat can only be used where additional layers will not be 

added. Vapor suppressed gel coat can be used to coat interior spaces of assembled boats 

where the gel coat is only being used as the final surface finish. Vapor suppressed gel 

coat is typically used in this application because the curing of all polyester resins is 

 

f

 “Primary bonds” are created when additional resin and fiberglass is applied to resin that is still wet and 

has not cured. “Secondary bonds” are created when additional resin and fiberglass is applied to resin that 

has fully cured, such as when parts are assembled and bonded together with more fiberglass and resin. 

APPENDIX E: CTG SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT August 18, 2011 E - 18 Final Staff Report with Appendices 

for Proposed Amendments to Rule 4684
11

inhibited by exposure to the air, and the wax additive ensures complete curing of the gel 

coat surface.g 

3. Non-atomizing Resin Application 

Changing resin application methods can also reduce monomer VOC emissions. 

For example, switching from atomizing to non-atomizing application of a resin with 35 

percent styrene achieves a 41 percent emission reduction. If both styrene content and 

application method are changed to reduce emissions, the reductions can be greater than 

changing just the resin styrene content or application method alone. For example, 

changing from atomized application of resin with 40 percent styrene, to resin with 35 

percent styrene that is applied with nonatomizing technology can achieve a 58 percent 

emission reduction. 

Currently, nonatomizing technology is feasible for applying production and 

tooling resins only. Gel coats must still be applied with atomizing spray guns, so 

monomer VOC reductions from gel coat can only be achieved through the use of low 

monomer VOC gel coats. The only exception is gel coat that may be applied with a 

brush or roller to the interior areas of finished boats where the cosmetic appearance is not 

as critical as on the exterior. 

 Non-atomized resin application includes five different techniques for applying 

resin: bucket and brush application by hand, resin rollers, flow coaters, resin 

impregnators, and fluid impingement technology. All five of these techniques reduce 

emissions compared to atomized resin spraying techniques by eliminating the atomization 

of resin. The emission reductions are generally greater for higher styrene resins. 

 Bucket and brush application is the oldest method of applying resin to fiberglass 

reinforcements. Individual batches of resin are mixed with a catalyst in a bucket or pail 

and applied to the part by hand using a brush or paint roller. This technique was the first 

method used in fiberglass boat manufacturing until spray equipment and chopper guns 

were developed for applying resin. Currently, it is used only in limited cases for low 

volume production or custom work, or for fabricating small parts and bonding parts at 

larger production facilities. 

 Pressure fed resin rollers consist of a fabric roller that is fed a continuous supply 

of resin from a mechanical fluid pump. The fluid pump draws resin from a drum or bulk 

distribution line. The resin pump is mechanically linked to a separate catalyst pump. 

These two pumps supply the resin and catalyst in a preset ratio to a mixer in the handle of 

the roller. The mixer then feeds the catalyzed resin to the roller head through the handle 

of the roller. A valve controlled by the operator regulates the amount of resin flowing to 

the roller head and to the part being fabricated. The roller head is covered with a 

disposable fabric cover similar to a standard paint roller cover. Resin rollers are intended 

to be operated almost continuously during a shift to prevent the resin from hardening 

 

g

 In other cases, the gel coat and resin becomes fully cured because the surface is blocked from the air by 

the subsequent layers of material that are added to the part. 

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between the mixer and the roller cover. At the end of the shift, the roller cover is 

discarded and the mixing unit, handle, and roller manifold are flushed with a solvent. 

 Flow coaters are similar to standard resin spraying equipment except that the 

resin leaves the tip of the flow coater in continuous consolidated streams rather than as an 

atomized spray. Whereas the tip of a spray gun is a single small orifice, the tip of a flow 

coater has a dozen or so precisely drilled holes that produce steady streams of resin, 

similar to a small showerhead. Flow coaters can also be fitted with a chopper head to 

apply chopped fiberglass roving in the same way as a conventional atomized chopper 

gun. The flow coaters use the same resin and catalyst pumps that are used with catalystinjected spray equipment or resin rollers. Like resin rollers and other internal mix 

equipment, flow coaters are intended to be operated almost continuously during a shift to 

prevent the resin from hardening inside the applicator. At the end of the shift, the gun 

and nozzle are flushed using a solvent. 

 Fabric impregnators use resin covered rollers to saturate fiberglass fabric, similar 

to an old-fashioned wringer washer in reverse. Dry fabric is fed down through a pair of 

finished-metal rollers that hold a reservoir of resin to impregnate or saturate the fabric. 

The gap between the rollers can be adjusted to achieve a predetermined fiber-to-resin 

ratio. Catalyzed resin can be manually mixed and poured into the machine or 

continuously mixed and fed to the machine by fluid pumps that are similar to those used 

for resin spray equipment. 

 Fabric impregnators are available in a variety of sizes. Small table top units are 

available for impregnating narrow reinforcing tapes. Larger impregnators can be 

mounted on mobile bridge cranes so that impregnated fabric can be lowered directly from 

the impregnator into a large open mold. 

Fluid impingement technology consists of a gun that dispenses two streams of 

resin that come together to form a fan of large droplets. The large size of the droplets 

minimizes emissions compared to atomized spray application. This technology is 

reported to be the most widely used non-atomizing technology used to apply resin. 

4. Closed Molding 

Closed molding is the name given to fabrication techniques in which reinforced 

plastic parts are produced between the halves of a two-part mold, or between a mold and 

a flexible membrane, such as a bag. There are four types of closed molding methods that 

are being used in fiberglass boat manufacturing: vacuum bagging, vacuum-assisted resin 

transfer molding, resin transfer molding, and compression molding with sheet molding 

compound. Closed molding processes as they are currently practiced cannot be used to 

reduce emissions during gel coat or skin coat application, because these applications must 

still use conventional open molding techniques. However, closed molding can be used to 

reduce monomer VOC emissions from the subsequent laminating steps after the gel coat 

and skin coat layers have been applied. 

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Closed molding is generally applicable to making a large number of small parts, 

such as hatches and locker doors, or small numbers of high performance boat hulls and 

decks, but it is not feasible to replace open molding with closed molding at all types of 

boat manufacturing facilities. However, as discussed below, one major fiberglass boat 

manufacturer has developed a patented closed molding process that has replaced open 

molding for the hulls of many of its smaller (17 to 22 feet long) powerboats. 

 Vacuum bagging is a partially closed molding technology. It uses techniques 

similar to open molding but with a modification in the resin curing stage. After resin and 

fiberglass have been applied, a flexible, clear plastic sheet is placed over the wet laminate 

and sealed along the edge of the mold to form a "bag." A porous material called a 

bleeder sheet is also placed under the bag and a hose connected to a vacuum pump is 

sealed under the edge of the bag. The vacuum pump is used to draw the air out from 

under the bag and press the bag down onto the part. The pressure of the vacuum removes 

any trapped air and excess resin from the part and presses the layers of laminated material 

together. This technique is used to increase the fiber-to-resin ratio, which generally 

increases the strength of a part, and also to obtain a good bond between FRP skins and 

non-FRP core materials, such as wood or foam. Core materials are often sandwiched 

between layers of FRP to make a thicker and stiffer part without significantly increasing 

the part's weight. The EPA believes that most facilities that perform vacuum bagging use 

it only for fabricating small parts and not for hulls, decks, and superstructures. 

 No data are available to quantify the emission reductions associated with vacuum 

bagging. However, approximately 50 percent of emissions during lamination occur 

during the curing stage after the resin has been applied. Since the vacuum bag covers the 

part during resin curing, vacuum bagging may reduce a significant fraction of these 

curing emissions. The emission reductions will depend on how quickly the resin is 

covered with the vacuum bag. 

 Vacuum-Assisted Resin Transfer Molding (VARTM) is a closed molding 

technology that uses a vacuum to pull resin into dry fiberglass reinforcements that are 

placed into a closed mold. The closed mold may be formed using a flexible plastic sheet 

or "bag" as in vacuum bagging, or by a rigid or semi-rigid cover that matches the shape 

of the mold. In all variations, the bag or cover is sealed to the mold and vacuum pressure 

is used to draw resin from an outside reservoir into the sealed mold through a system of 

distribution tubes and channels placed under the bag or cover. 

 One VARTM process that has been used by several boat manufacturers is a 

patented technology called the Seeman Composites Resin Infusion Molding Process 

(SCRIMP) which is licensed by SCRIMP Systems, LLC. In the SCRIMP process, the 

mold is coated with a gel coat finish and a skin coat is applied using conventional 

techniques. Dry reinforcements and core materials are then placed in the mold. The resin 

distribution system and the bag are then placed over the mold and sealed to the edge of 

the mold. The vacuum is then applied to pull the bag against the mold and the 

reinforcements and the bag is checked for leaks. Valves to the resin supply system are 

then opened and the resin is pulled into the reinforcements by the vacuum. When the 

reinforcements are thoroughly saturated with resin, the resin supply is shut off and the 

APPENDIX E: CTG SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT August 18, 2011 E - 21 Final Staff Report with Appendices 

for Proposed Amendments to Rule 4684
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part is allowed to cure under a vacuum. After curing, the bag is removed and is either 

discarded or reused, depending on the material from which it is made. Disposable bags 

are made from plastic film, whereas reusable bags are made from silicone rubber. A 

silicone bag can be used for more than 500 parts. 

 Another patented closed molding process is called the Virtual Engineered 

Composites® (VEC®) process. In this process, resin is injected into a rigid closed mold 

that is already loaded with the dry fiberglass reinforcements. The process is computer 

controlled and the mold components can be reused many times. The company that owns 

this process has used it to replace open molding in the manufacture of relatively large 

numbers of small (17 to 22 foot) powerboats. 

 The VARTM and VEC® processes can significantly reduce emissions during 

lamination because the resin is drawn from a bulk container and distributed under an 

airtight bag or cover, so very little resin is exposed to the atmosphere. These processes as 

they are currently practiced cannot be used to reduce emissions during gel coat and skin 

coat application because these steps must still use conventional open molding techniques. 

 Resin transfer molding (RTM) uses two rigid mold halves to provide the shape for 

fabrication of FRP boat parts. In a typical RTM operation, gel coat is spray applied to the 

inside surface of both halves of the mold so that the part has two finished sides, instead of 

one as in open molding. After the gel coat cures, the dry reinforcement is laid inside the 

mold and the mold is closed with clamps. When closed, the two halves of the mold mate 

together with a narrow space between them equal to the thickness of the finished part. 

Catalyzed resin is injected into the closed mold where it saturates the fiberglass. While 

the part is still in the mold, the resin cures. After the resin has cured, the mold is opened 

and the finished part is removed. 

 The RTM process is most economical for making many copies of small parts, 

especially when a smooth finish is desired on both sides of the part. Typical applications 

of RTM in boat manufacturing are for making hatch covers, doors, and seats. No 

emissions data are available from the RTM process; however, because the resin is not 

exposed to the air during application or curing, the EPA predicts that little monomer 

VOC is emitted during fabrication by RTM compared to conventional hand and spray 

processes. Any monomer VOC that is emitted is released during off-gassing when the 

mold is opened. 

 Compression molding involves the use of a prepared compound such as sheet 

molding compound (SMC) and a large hydraulic press to produce FRP parts. The 

prepared SMC sheet is composed of resin and fiberglass fibers. To create a FRP part with 

compression molding, SMC sheets are cut to the proper size and put into a matched male 

and female mold. The two molds are pressed together in the hydraulic press under several 

tons of pressure. The SMC is forced into all areas of the mold and cures in the closed 

mold under high heat and pressure in a matter of minutes. Several facilities are currently 

using compression molding with SMC to produce hulls, decks, and other parts for 

personal watercraft (PWC), such as those known under the trade name Jet Ski®. 

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for Proposed Amendments to Rule 4684
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 No emissions data are available from the compression molding with SMC 

process; however, because the resin is not exposed to the air during application or curing, 

the EPA predicts that little monomer VOC is emitted during fabrication with SMC 

compared to open molding resin application processes. 

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for Proposed Amendments to Rule 4684
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5. Add-On Control Systems 

No facilities in the fiberglass boat manufacturing industry currently use add-on 

controls to reduce VOC emissions. The majority of VOC emissions from resin and gel 

coat in an open molding process occur in an open shop environment. Some emissions 

occur in spray booths where gel coat spraying for smaller parts may be done. The 

volume of air exhausted from the open shop or from spray booths is typically high, and 

the VOC concentration is typically low. Therefore, it is not cost-effective to use add-on 

controls to reduce VOC emissions from fiberglass boat manufacturing. Because of the 

wide availability and lower cost (compared to add-on controls) of low-monomer VOC 

content materials and alternative application methods, these materials and methods are 

used to reduce monomer VOC emissions from fiberglass boat manufacturing facilities. 

B. Available Control Options for Mixing Containers

Resin and gel coat materials are usually stored and prepared for application in 

large containers, either large stationary tanks or 55 gallon drums. Before application, 

promoters may be added to the material to promote the cross linking reaction after the 

resin is mixed with catalyst. Thixotropic agents may also be added so that resin and gel 

coat will hold onto vertical surfaces without running while still in a liquid state. Since 

the material in these containers may be agitated to mix in these additives and to keep 

them mixed in during application, these containers are a potential source of VOC 

emissions. 

To reduce VOC emissions from tanks or drums used to mix materials containing 

VOC, these containers can be sealed with tightly fitting covers during mixing operations. 

These covers can be modified with openings to allow the mixing and pumping equipment 

into the container, but these openings can also be sealed to reduce VOC emissions. 

C. Available Control Options for Cleaning Materials

Organic solvents are commonly used to clean application equipment, including 

resin and gel coat spray guns and other mechanical applicators, as well as rollers and 

other hand tools. These organic solvents include acetone, methyl ethyl ketone (MEK), 

lacquer thinner, Stoddard solvent, or toluene. Water-based emulsifiers with low VOC 

content and organic solvents with low vapor pressures can also be used to clean the 

application equipment. 

To control VOC emissions from cleaning materials, facilities can use water-based 

emulsifiers that are low VOC, as well as organic solvents (e.g., dibasic esters, DBE) with 

low vapor pressures. Commonly used water-based emulsifiers in the fiberglass boat 

manufacturing industry contain less than 5 percent VOC by weight. Dibasic esters have 

vapor pressures of 0.5 mm Hg or less, at 68 ° F, so they have very low evaporation rates 

and little of the material is lost during use. These materials can typically be recovered 

and recycled by the vendor. Many facilities already use both water-based emulsifiers and 

DBE to clean resin and gel coat application equipment. 

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for Proposed Amendments to Rule 4684
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D. Existing Federal, State, and Local Recommendations/Regulations

 The following discussion is a summary of EPA, State, and local actions that 

address VOC emissions from fiberglass boat manufacturing. 

1. The 1990 National VOC Assessment 

In 1990, the EPA completed an “Assessment of VOC Emissions from Fiberglass 

Boat Manufacturing” (EPA/600/S2-90/019). This document characterized the fiberglass 

boat manufacturing industry and its processes, assessed the extent of VOC emissions 

from this industry, and evaluated various control options. The assessment described open 

molding and discussed types of closed molding in use at the time. The assessment 

determined that acetone (no longer considered a VOC) and styrene were the two primary 

VOC emitted from the industry, and the major sources of emissions were resin and gel 

coat applications, and evaporation of solvents during clean-up. 

 The 1990 assessment discussed process changes and add-on controls to reduce 

emissions. Specifically, it recommended substituting the high-VOCh

 resins and gel coats 

that were commonly used at that time with low-VOC resins (e.g., 35 percent styrene) and 

gel coats, and vapor suppressed resins. The document discussed add-on controls, but 

considered such controls not economically feasible for use in fiberglass boat 

manufacturing due to high exhaust flow rates and low VOC concentrations. The 

document also recommended using water-based emulsifiers and low vapor pressure 

dibasic ester (DBE) compounds for equipment cleaning. 

2. The 2001 NESHAP for Boat Manufacturing 

In 2001, EPA promulgated the National Emission Standards for Hazardous Air 

Pollutants for Boat Manufacturing, 40 CFR part 63, subpart VVVV (2001 NESHAP). 

The 2001 NESHAP established organic hazardous air pollutant (HAP) emissions limits 

based on low-HAP resins and gel coats and low-emitting resin application technology. It 

also established limits to reduce emissions from cleaning operations and resin and gel 

coat mixing containers. 

 The 2001 NESHAP applies to fiberglass boat manufacturers that are major 

sources of HAP emissions. Major sources are stationary sources that emit, or have 

the potential to emit, (considering controls) 10 tpy or more of any one HAP, or 25 

tpy or more of any combination of HAP. The 2001 NESHAP regulated the 

following, with certain exceptions: 

• All open molding operations, including pigmented gel coat, clear gel coat, 

production resin, tooling resin, and tooling gel coat; 

• All closed molding resin operations; 

• All resin and gel coat application equipment cleaning; and 

 

h

 In this 1990 document, the authors did not distinguish between monomer and non-monomer VOC. 

APPENDIX E: CTG SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT August 18, 2011 E - 25 Final Staff Report with Appendices 

for Proposed Amendments to Rule 4684
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• All resin and gel coat mixing operations. 

The 2001 NESHAP regulates the total HAP content in the materials used in each 

regulated operation. Specifically, the 2001 NESHAP sets a HAP content limit for each 

regulated open molding resin and gel coat operation. For each regulated open molding 

resin operation, the NESHAP established separate HAP content limits for atomized and 

non-atomized resin application methods. A summary of the limitations is provided in 

Table 1 of this CTG. 

Table 1. Organic HAP Content Requirements for Open Molding Resin and 

Gel Coat Operations as Specified in the NESHAP for Boat Manufacturing 

(40 CFR 63, Subpart VVVV) 

For this operation-- And this application method 

-- 

Subpart VVVV provides 

that you must not exceed 

this weighted-average 

organic HAP content 

(weight percent) 

requirement -- 

Production resin operations Atomized 28 

Production resin operations Nonatomized 35 

Pigmented gel coat 

operations 

Any method 33 

Clear gel coat Any method 48 

Tooling resin operations Atomized 30 

Tooling resin operations Nonatomized 39 

Tooling gel coat operations Any method 40 

For closed molding operations, no limits apply to the resin application operation if 

it meets the specific definition of closed molding provided in the NESHAP. If a molding 

operation does not meet the definition of closed molding that is provided in the 

NESHAP, then it must comply with the applicable emission limits for open molding. 

A manufacturer can demonstrate compliance with the HAP emissions limit for the 

facility by any of the following alternatives, either alone or in combination: 

• Ensure that all materials used in a particular open molding operation meet 

the HAP content requirements summarized in Table 1; 

• Comply with the HAP content requirements in Table 1 on a weightedaverage basis for all materials used within an operation, calculated on a 

rolling 12-month compliance period; 

• Averaging emissions among operations and ensure that overall emissions 

do not exceed those that would occur if each operation complied 

separately using low-HAP materials and application methods. The facility 

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for Proposed Amendments to Rule 4684
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would use “MACT Model Point Value Formulas” provided in the 

NESHAP to estimate HAP emission rates (kg HAP/Mg material used) for 

each operation and to average among operations. The facility would also 

use a separate equation in the rule to estimate the emissions that would 

occur if each operation complied separately using low-HAP materials and 

application methods; or 

• Use an emission capture system and add-on control device to ensure that 

overall emissions do not exceed those that would occur if each operation 

complied separately using low-HAP materials and application methods. 

In addition to the resin and gel coat open molding operations which, as described 

above, are subject to HAP content limits or emission rate limits, other operations are 

subject to either work practice requirements or HAP content limits in the 2001 NESHAP. 

These operations include resin and gel coat mixing operations in tanks or drums, and 

routine resin and gel coat application equipment cleaning operations. 

Resin and gel coat mixing containers with a capacity of 208 liters (55 gallons) or 

more must be covered with tightly fitted lids. Routine resin and gel coat application 

equipment cleaning operations must use solvents containing no more than 5 percent 

HAP, but solvents used to remove cured resin or gel coat from equipment are exempt 

from the HAP content limits. However, the containers used to hold the exempt solvent 

and to clean equipment with cured resin and gel coat must be covered, and there is an 

annual limit on the amount of exempt solvent that can be used. 

3. Existing State and Local VOC Requirements 

 Five States, including California, that have fiberglass boat manufacturing 

facilities have State and local regulations to address VOC emissions from fiberglass boat 

manufacturing. These rules limit VOC emissions from all types of polyester resin 

operations, and treat fiberglass boat manufacturing as a subset of polyester resin 

operations. In California, 16 Air Quality Management Districts (AQMDs) have 

regulations for polyester resin operations; there is no statewide rule. The other States 

with regulations that address polyester resin operations are Illinois (the Chicago area), 

Indiana, Maryland, and Washington (only in the Puget Sound area). 

 The existing State regulations are summarized in Table 2. For California, we 

have summarized only a representative sample of the regulations from the 16 AQMDs. 

The South Coast Air Quality Management District (SCAQMD) has the most stringent 

State or local regulation. Specifically, SCAQMD Rule 1162, (Polyester Resin 

Operations) contains monomer VOC content limits for specific types of resins, gel coats, 

and cleaning solvents. Furthermore, Rule 1162, requires that all resins have to be applied 

with non-atomizing techniques, such as resin rollers, flow coaters, or hand lay up. Rule 

1162 also requires that gel coat must be applied with high efficiency spray equipment, 

such as high-volume low-pressure (HVLP), air assisted airless, or electrostatic spray. 

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However, the SCAQMD regulation is not as stringent as the 2001 NESHAP.i The other 

AQMD rules in California do not require the use of non-atomized spray application, but 

specify that all material spraying use high efficiency spray equipment. The other AQMD 

rules also tend to be less stringent than South Coast Rule 1162 because they have higher 

allowable monomer VOC contents for resin and gel coat. 

 The Illinois rule for the Chicago area, and the Maryland and Puget Sound rules 

also require the use of high efficiency spray techniques, but only the Chicago and 

Maryland rules have limits for the monomer VOC content of resin and gel coat materials. 

These rules are also less stringent than the 2001 NESHAP. 

 The Indiana rule has adopted a different approach from other state VOC rules. 

The Indiana rule recognizes that since the primary VOC from fiberglass boat 

manufacturing (styrene and MMA) are also HAP, compliance with the 2001 NESHAP 

achieves nearly equal VOC and HAP emission reductions. Therefore, the Indiana rule 

provides that compliance with the 2001 NESHAP will satisfy the need to achieve best 

available control technology (BACT) for new sources that are constructed after 1980. 

There are no separate standards for RACT for existing sources in the Indiana rule, but it 

is assumed that the 1980 date for new sources will mean that most sources are covered by 

the BACT requirement. 

 The local and State rules that have been identified also address application 

equipment cleaning operations, either through work practices or VOC content limits on 

cleanup materials. Some rules prohibit the use of VOC cleaning solvents, or set very low 

VOC limits. This is possible since acetone and methylene chloride, which are 

specifically exempted from the EPA's definition of VOC in 40 CFR 51.100(s), can be 

used as clean up solvents. However, boat manufacturers prefer to avoid using acetone 

because it is highly flammable, and the use of methylene chloride (a HAP) is regulated at 

sources that need to comply with the 2001 NESHAP. 

Table 2. Summary of State and Local Requirements for VOC Emissions from 

Fiberglass Boat Manufacturing 

State 

Local Area 

Applies to VOC Limit 

Applies To 

Monomer VOC 

Limit 

(Wt% monomer 

VOC in material 

unless noted 

otherwise) 

Work and 

Equipment 

Practices 

General Purpose 

Polyester Resin 

California 35 

South Coast 

AQMD Rule 1162 

All polyester resin 

operations that 

fabricate, rework, 

repair, 

or touch-up 

products for 

commercial, 

CorrosionResistant Resin 

(definition 

includes boat hulls 

and tooling/molds) 

48 

Must use nonatomized 

application for 

resin. 

Must use highefficiency spray 

techniques for gel 

 

i

 Since styrene and MMA are the primary VOC, as well as the primary HAP, emitted from resin and gel 

coat, the HAP limits in the NESHAP and the monomer VOC limits in State and local rules can be 

compared directly. 

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State 

Local Area 

Applies to VOC Limit 

Applies To 

Monomer VOC 

Limit 

(Wt% monomer 

VOC in material 

unless noted 

otherwise) 

Work and 

Equipment 

Practices 

Fire Retardant 

Resin 

38 

High Strength 

Resin (definition 

includes highperformance boats) 

40 

Clear Gel Coat 44 

Pigmented Gel Coat: 

White and off 

white: 

45 

Non-White: 37 

Primer: 28 

Specialty Gel Coat 

(used with 

corrosion resistant, 

fire retardant, or 

high strength 

resins) 

48 

Closed Molding 4% maximum 

weight loss during 

curing 

military, or 

industrial use 

Solvent cleaning 

of equipment: 

Comply with 

AQMD Rule 1171 

VOC content limit 

= 25 g/liter 

(0.21 lb/gal) 

coat. 

General Purpose 

Polyester Resin 

35 

CorrosionResistant or Fire 

Retardant Resin 

50 

Gel coat 250 g VOC/liter of 

coating applied 

California 

Bay Area AQMD 

Rule 8-50 

The manufacturing 

of products using 

polyester resins. 

Exempts touch up 

and repair during 

manufacture. 

Cleaning Materials 200 g VOC/liter of 

cleaning material 

Must use high 

efficiency spray 

equipment for any 

spray operations. 

Use collecting 

system if organic 

solvents are used 

for equipment 

cleaning. 

General Purpose 

Polyester Resin 

California 35 

San Diego APCD 

Rule 67-12 

Polyester resin 

operations, except 

marine vessel 

repair operations 

CorrosionResistant or Fire 

50 

Must use high 

efficiency spray 

equipment for any 

spray operations, 

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State 

Local Area 

Applies to VOC Limit 

Applies To 

Monomer VOC 

Limit 

(Wt% monomer 

VOC in material 

unless noted 

otherwise) 

Work and 

Equipment 

Practices 

Restardant Resin 

Pigmented gel 

coats 

45 

Clear gel coats 50 

that use less than 

0.5 gallons of 

material per 

operating day. 

Cleaning materials 200 g VOC/liter, 

or, a boiling point 

>190 C, or use a 

VOC reclamation 

system (onsite or 

offsite), or use less 

than 0.5 gallons 

average per day 

except for touch up 

and repair using a 

spray gun with a 

container as part of 

the gun. 

General Purpose 

Polyester Resin 

35 

CorrosionResistant or Fire 

Retardant Resin 

50 

Pigmented gel 

coats 

45 

California 

Santa Barbara 

APCD Rule 349 

Apply to all 

commercial and 

industrial polyester 

resin operations 

that use 50 or more 

gallons of styrene 

per year. 

Clear gel coats 50 

Must use high 

efficiency spray 

equipment for any 

spray operations. 

CorrosionResistant or Fire 

Retardant Resin 

48 

High Strength 

(>10,000 psi 

tensile strength), 

including tooling 

resins 

48 

Clear gel coats 50 

Pigmented gel coat 45 

Illinois 

Rule 218, Subpart 

CC 

Chicago Area 

All other materials 35 

Must use high 

efficiency spray 

equipment for any 

spray operations. 

Indiana Rule 

326 IAC 8-1-6 

New sources 

(constructed after 

1980) that emit 

more than 25 tons 

per year of VOC. 

Compliance with 40 CFR 63 subpart VVVV satisfies BACT. 

A case-by-case BACT determination is not needed. 

No separate standards are specified for RACT. 

General Purpose 

Polyester Resin 

35 

High Strength, 

CorrosionResistant, or Fire 

Retardant Resin 

50 

Gel coat 50 

Maryland 

Rule 26.11.19.26 

Applies where the 

total VOC from all 

RPC 

manufacturing is 

20 pounds or more 

per day. Does not 

apply to resins 

used for tooling or 

touch up and 

repair. 

Cleanup materials Use non-VOC 

cleanup materials 

If VOC emissions 

are 100 pounds or 

more per day, use 

airless or airassisted spray guns 

or non-atomized 

application 

methods for 

general purpose 

resin application. 

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State 

Local Area 

Applies to VOC Limit 

Applies To 

Monomer VOC 

Limit 

(Wt% monomer 

VOC in material 

unless noted 

otherwise) 

Work and 

Equipment 

Practices 

Washington 

Puget Sound Clean 

Air Agency 

Regulation II, 

Article 3, Section 

3.08 

Manufacturing 

operations 

involving the use 

of polyester, 

vinylester, gelcoat, 

or resin in which 

the styrene 

monomer is a 

reactive monomer 

for the resin. 

Allows atomized spraying, but requires use of higher efficiency 

spray methods (e.g., HVLP, airless, air assisted airless). 

No monomer VOC content limits on materials. 

VOC materials used for cleanup must be collected in a closed 

container. 

VI. Recommended Control Options

We are recommending that this CTG covers the following operations: 

• Open molding resin and gel coat operations (these include pigmented gel coat, 

clear gel coat, production resin, tooling gel coat, and tooling resin); 

• Resin and gel coat mixing operations; and 

• Resin and gel coat application equipment cleaning operations. 

Based on a review of the 2001 NESHAP, and the current State and local 

requirements discussed above, we are recommending monomer VOC content limits 

and alternative monomer VOC emission rate limits for resin and gel coats used in open 

molding operations. The monomer VOC content limits are paired with specific 

methods (either atomized or non-atomized) for resin application. In addition, we are 

recommending a non-monomer VOC content limit for resins and gel coats used in open 

molding operations. We are also recommending work practices to reduce VOC 

emissions from resin and gel coat mixing containers, and VOC content and vapor 

pressure limits for cleaning materials. Our recommendations are described in more 

detail below. 

A. Recommended VOC Limits for Gel Coats and Resins

We are recommending monomer VOC content limits and alternative monomer 

VOC emission rate limits for open molding operations. Our recommended monomer 

VOC content and emission rate limits are based on the 2001 NESHAP for boat 

manufacturing. As previously discussed in section IV.B of this CTG, styrene and MMA, 

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which are the primary VOC emitted from resins and gel coats used in fiberglass boat, are 

the only monomer VOC we have identified in these resin and gel coat materials. Because 

styrene and MMA are also the primary HAP emitted by this industry, the HAP limits in 

the 2001 NESHAP are equally effective in reducing monomer VOC emissions from the 

resins and gel coats used in fiberglass boat manufacturing. As mentioned above, the 

2001 NESHAP limits are more stringent than the limits provided in other Federal, State, 

or local actions for the control of monomer VOC emissions from fiberglass boat 

manufacturing. Based on the implementation of the NESHAP limits by all major source 

fiberglass boat manufacturers, the general availability of the resins and gel coats that 

meet the 2001 NESHAP limits, and the shift of the fiberglass boat manufacturing 

industry (including area source fiberglass boat manufacturers) to non-atomized resin 

application methods, we believe that the monomer VOC limits recommended in this CTG 

are technically and economically feasible for fiberglass boat manufacturers in ozone nonattainment areas. 

Further, as previously mentioned, resins and gel coats used in fiberglass boat 

manufacturing may also contain non-monomer VOC, and they constitute less than 5 

percent of the total VOC in all resins and gel coats and usually comprise less than 1 

percent of each resin or gel coat, by weight. Accordingly, we are also recommending a 

non-monomer VOC content limit of no more than 5 percent by weight of the resin or gel 

coat. This recommended limit on non-monomer VOC is in addition to the separate 

monomer VOC limits being recommended for resin and gel coat. Based on our 

recommendation, if the non-monomer VOC content of a resin or gel coat exceeds 5 

percent, then the excess non-monomer VOC over 5 percent would be counted toward the 

monomer VOC content. For example, if a resin contains 6 percent non-monomer VOC 

and 34 percent monomer VOC, then 1 percent (the amount in excess of 5 percent) of the 

non-monomer VOC would be counted as a monomer VOC, and the resin would be 

considered as having a monomer VOC content of 35 percent. 

 We recommend that the monomer VOC content of resin and gel coat 

materials be determined using SCAQMD Method 312-91, Determination of Percent 

Monomer in Polyester Resins, revised April 1996. In addition, we recommend that 

manufacturer’s formulation data be accepted as an alternative to this method. If there is a 

disagreement between manufacturer's formulation data and the results of a subsequent 

test, we recommend that States use the test method results unless the facility can make a 

demonstration to the States' satisfaction that the manufacturer's formulation data are 

correct.The recommended monomer and non-monomer VOC limits in this CTG do not 

apply to closed molding operations that meet the same definition of closed molding that 

is found in the 2001 NESHAP. We recommend that closed molding operations that do 

not meet this definition, such as vacuum bagging operations, meet the monomer and nonmonomer VOC limits for open molding operations. That definition of closed molding is 

as follows: 

“Closed molding means any molding process in which pressure is used to 

distribute the resin through the reinforcing fabric placed between two mold 

surfaces to either saturate the fabric or fill the mold cavity. The pressure may be 

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clamping pressure, fluid pressure, atmospheric pressure, or vacuum pressure used 

either alone or in combination. The mold surfaces may be rigid or flexible. Closed 

molding includes, but is not limited to, compression molding with sheet molding 

compound, infusion molding, resin injection molding (RIM), vacuum assisted 

resin transfer molding (VARTM), resin transfer molding (RTM), and vacuumassisted compression molding. Processes in which a closed mold is used only to 

compact saturated fabric or remove air or excess resin from the fabric (such as in 

vacuum bagging), are not considered closed molding. Open molding steps, such 

as application of a gel coat or skin coat layer by conventional open molding prior 

to a closed molding process, are also not closed molding.”j

Consistent with the framework established in the NESHAP, we are 

recommending that the recommended open molding monomer and non-monomer VOC 

limits described above not be applied to the following three types of materials at 

fiberglass boat manufacturing facilities. We are making this recommendation because 

the following three materials must be formulated to meet specific performance 

requirements, making it infeasible to reduce monomer and non-monomer VOC contents 

below their existing levels. We are making different recommendations for the materials 

identified below, and those recommendations are noted below: 

(1) Production resins (including skin coat resins) that must meet specifications 

for use in military vessels or must be approved by the U.S. Coast Guard for use in the 

construction of lifeboats, rescue boats, and other life-saving appliances approved under 

46 CFR subchapter Q, or the construction of small passenger vessels regulated by 46 

CFR subchapter T. Production resins that meet these criteria can still be applied with 

nonatomizing resin application equipment, and we are recommending this as a control 

option for these resins 

(2) Production and tooling resins, and pigmented, clear, and tooling gel coat used 

for part or mold repair and touch up. We recommend that the total resin and gel coat 

materials that meet these criteria not exceed 1 percent by weight of all resin and gel coat 

used at a facility on a 12-month rolling-average basis. 

(3) Pure, 100-percent vinylester resin used for skin coats. We recommend that 

the monomer and non-monomer VOC limits not be applied to pure, 100-percent 

vinylester resin used for skin coats. We still recommend these monomer and nonmonomer VOC limits for blends of vinylester and polyester resins used for skin coats. 

Pure, 100-percent vinylester resin used for skin coats can be applied with nonatomizing 

resin application equipment, and we recommend this as a control option for this type of 

resin. We also recommend that the total amount of resin materials meeting this criteria 

not exceed 5 percent by weight of all resin used at a facility on a 12-month rollingaverage basis. 

The CTG provides flexibility by recommending the same options for meeting 

the monomer VOC limits as provided in the 2001 NESHAP for meeting the HAP 

 

j

 40 CFR 63, subpart VVVV, §63.5779. 

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emission limits. To meet the recommended open molding resin and gel coat limits, the 

CTG recommends three options: (1) achieving the individual monomer VOC content 

limit through the use of low-monomer VOC materials, either by using only lowmonomer VOC materials within a covered operation (as listed below in VI.A), or by 

averaging the monomer VOC contents for all materials used within an operation on a 

weight-adjusted basis; (2) meeting the numerical monomer VOC emission rate limits, 

which would enable a facility to average emissions among different operations using 

equations to estimate monomer VOC emission rates from each operation based on the 

material and application method; or (3) using add-on controls to achieve a numerical 

monomer VOC emission rate that is determined for each facility based on the mix of 

application methods and materials used at that facility. 

The emission reductions that are achieved using the emissions averaging option 

(Option 2) and the add-on control option (Option 3) are equivalent to the emission 

reductions that are achieved by meeting the monomer VOC content limits (Option 1). 

Options 2 and 3 use emission factor equations to convert the monomer VOC content 

limits in Option 1 into equivalent monomer VOC emission rates that a facility would 

otherwise achieve by using the low-monomer VOC materials for specific application 

methods and operations. 

A facility could use emission averaging (Option 2) or add-on controls (Option 3) 

for all open molding operations or only for some of the operations. Operations that a 

facility decides not to include in Options 2 or 3 would use Option 1. For filled resins, 

which are discussed in more detail in section VI. B, the CTG includes an adjustment 

factor that would allow filled resins to use any of the three options recommended above. 

We are recommending that all three of these options be included in what States 

determine constitutes RACT for VOC emissions from these operations. That is, we are 

recommending that States not include just one option and exclude the other two. All 

three options are recommended to be included, together, so as to provide flexibility to 

facilities as they reduce their VOC emissions in response to State RACT determinations. 

Our recommendations, as described above, are consistent with the approach and 

flexibility we provided in the 2001 NESHAP for Boat Manufacturing. 

We are also recommending that State RACT determinations allow facilities to use 

a combination of all three options at a single facility. For example, a facility could use 

emissions averaging (Option 2) for only a subset of materials and activities and Option 1 

for the rest of the materials and activities at the facility. Our recommendations, as 

described above, are consistent with the approach and flexibility we provided in the 2001 

NESHAP for Boat Manufacturing. 

 1. Compliant Materials Option 

 Under this option, facilities would use resins and gel coats that meet the 

applicable recommended monomer VOC content limits in Table 3 of this CTG and the 

non-monomer VOC content limit of 5 percent. We recommend that the applicable limits 

be considered met if all materials of a certain type (e.g., production resin, pigmented gel 

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coat) meet the applicable monomer and non-monomer VOC content limits for a specific 

application method. 

Table 3. Compliant Materials Monomer VOC Content Recommendations for Open 

Molding Resin and Gel Coat. 

For this material-- And this application method 

-- 

This weighted average 

monomer VOC content 

(weight percent) limit is 

recommended -- 

Production resin Atomized (spray) 28 

Production resin Nonatomized 35 

Pigmented gel coat Any method 33 

Clear gel coat Any method 48 

Tooling resin Atomized 30 

Tooling resin Nonatomized 39 

Tooling gel coat Any method 40 

 Alternatively, the applicable recommended limits in Table 3 above would be 

considered met if all materials of a certain type meet the applicable monomer VOC 

content limit for a specific application method on a weighted-average basis, and each 

resin and gel coat did not contain more than 5 percent non-monomer VOC. The 

weighted-average monomer VOC content would be determined based on a 12-month 

rolling average. A facility would use Equation 1 to determine weighted-average 

monomer VOC content for a particular open molding resin or gel coat material. 

 Equation 1: 

( )

∑( )

∑

=

= = n

i

i

n

i

ii

M

VOCM

Weighted Average Monomer VOC Content

1

1

Where: 

 Mi = mass of open molding resin or gel coat i used in the past 12 months 

in an operation, megagrams. 

 VOCi = Monomer VOC content, by weight percent, of open molding resin 

or gel coat i used in the past 12 months in an operation. 

 n = number of different open molding resins or gel coats used in the 

past 12 months in an operation. 

2. Emissions Averaging Option 

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 Under this option, monomer VOC emissions from the open molding resin and gel 

coat operations that a facility chooses to include in this emission average option would 

meet a facility-specific monomer VOC mass emission limit (12-month rolling average) 

that is determined using Equation 2. All resins and gel coats included in this option 

would also need to meet the recommended non-monomer VOC content limit of 5 percent. 

 Equation 2: 

Monomer VOC Limit = 46(MR) + 159(MPG) + 291(MCG) + 54(MTR) + 214(MTG) 

Where: 

 Monomer VOC Limit= total allowable monomer VOC that can be emitted 

 from the open molding operations included in the 

 average, kilograms per 12-month period. 

 MR = mass of production resin used in the past 12 months, excluding any 

materials that are exempt, megagrams. 

 MPG = mass of pigmented gel coat used in the past 12 months, excluding 

any materials that are exempt, megagrams. 

 MCG = mass of clear gel coat used in the past 12 months, excluding any 

materials that are exempt, megagrams. 

 MTR = mass of tooling resin used in the past 12 months, excluding any 

materials that are exempt, megagrams. 

 MTG = mass of tooling gel coat used in the past 12 months, excluding any 

materials that are exempt, megagrams. 

The numerical coefficients associated with each term on the right hand side of 

Equation 2 are the allowable monomer VOC emission rate for that particular material in 

units of kg/Mg of material used. 

For those materials that are not included in the emissions average, the facility 

would resort to one of the other two recommended options for limiting monomer and 

non-monomer VOC emissions from resins and gel coats. 

We recommend that the emissions average be calculated on a 12-month rollingaverage basis and determined at the end of every month (12 times per year). We further 

recommend that at the end of the first 12-month averaging period and at the end of every 

subsequent month, a facility use Equation 3 to show that the monomer VOC emissions 

from the operations included in the average do not exceed the emission limit calculated 

using Equation 2 for the same 12-month period. (A facility would include in Equations 2 

and 3 the terms for only those operations and materials included in the average.) 

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Equation 3: 

Monomer VOC emissions = (PVR)(MR) + (PVPG)(MPG) + (PVCG)(MCG) + 

 (PVTR)(MTR) + (PVTG)(MTG) 

Where: 

Monomer VOC emissions = Monomer VOC emissions calculated using the monomer 

VOC emission equations for each operation included in the 

average, kilograms. 

PVR = Weighted-average monomer VOC emission rate for production 

resin used in the past 12 months, kilograms per megagram. 

MR = Mass of production resin used in the past 12 months, 

megagrams. 

PVPG = Weighted-average monomer VOC emission rate for pigmented 

gel coat used in the past 12 months, kilograms per megagram. 

MPG = Mass of pigmented gel coat used in the past 12 months, 

megagrams. 

PVCG = Weighted-average monomer VOC emission rate for clear gel 

coat used in the past 12 months, kilograms per megagram. 

 MCG = Mass of clear gel coat used in the past 12 months, megagrams. 

 PVTR = Weighted-average monomer VOC emission rate for tooling 

resin used in the past 12 months, kilograms per megagram. 

 MTR = Mass of tooling resin used in the past 12 months, megagrams. 

PVTG = Weighted-average monomer VOC emission rate for tooling gel 

coat used in the past 12 months, kilograms per megagram. 

MTG = Mass of tooling gel coat used in the past 12 months, 

megagrams. 

For purposes of Equation 3, a facility would use Equation 4 to compute the 

weighted-average monomer VOC emission rate for the previous 12 months for each open 

molding resin and gel coat operation included in the average. 

Equation 4: 

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Where: 

 PVOP = weighted-average monomer VOC emission rate for each open 

molding operation (PVR, PVPG, PVCG, PVTR, and PVTG) 

included in the average, kilograms of monomer VOC per megagram 

of material applied. 

 Mi = mass of resin or gel coat i used within an operation in the past 12 

months, megagrams. 

 n = number of different open molding resins and gel coats used within 

an operation in the past 12 months. 

 PVi = the monomer VOC emission rate for resin or gel coat i used within 

an operation in the past 12 months, kilograms of monomer VOC per 

megagram of material applied. Use the equations in Table 4 to 

compute PVi

. 

Table 4. Monomer VOC Emission Rate Formulas for Open Molding 

Operationsk

For this material ... and this application method... 

Use this formula to calculate 

the monomer VOC emission 

rate... 

a. Atomized 0.014 x (Resin VOC%)2.425 

b. Atomized, plus vacuum 

bagging with roll-out 

0.01185 x (Resin VOC%)2.425

c. Atomized, plus vacuum 

bagging without roll-out 

0.00945 x (Resin VOC%)2.425

d. Nonatomized 0.014 x (Resin VOC%)2.275

e. Nonatomized, plus vacuum 

bagging with roll-out 

0.0110 x (Resin VOC%)2.275

1. Production resin, 

tooling resin 

f. Nonatomized, plus vacuum 

bagging without roll-out 

0.0076 x (Resin VOC%)2.275

 

k

 The formulae in this table were developed from EPA and industry-sponsored measurements of VOC 

emissions from resin and gel coat used in open molding. 

( )

∑( )

∑

=

= = n

i

i

n

i

ii

OP

M

PVM

PV

1

1

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2. Pigmented gel 

coat, clear gel coat, 

tooling gel coat 

All methods 0.445 x (Gel coat VOC%)1.675

 The formulas in Table 4 calculate monomer VOC emission rates in kilograms of 

monomer VOC per megagram of resin or gel coat applied. The formulas for vacuum 

bagging with roll-out are applicable when a facility rolls out the applied resin and fabric 

prior to applying the vacuum bagging materials. The formulas for vacuum bagging 

without roll-out are applicable when a facility applies the vacuum bagging materials 

immediately after resin application without rolling out the resin and fabric. VOC% = 

monomer VOC content as supplied, expressed as a weight-percent value between 0 and 

100 percent. 

3. Add-on Control Option

 If product performance requirements or other needs dictate the use of highermonomer VOC materials than those that would meet the recommended emission limits in 

Table 3, a facility could choose to use add-on control equipment to meet the emission 

limit determined by Equation 2. However, instead of using the mass of each material 

used over the past 12 months in Equation 2, the facility would use the mass of each 

material used during the control device performance test in Equation 2 to determine the 

emission limit (in kg of monomer VOC) that is applicable during the test. If the 

measured emissions at the outlet of the control device (in kg of monomer VOC) are less 

than the emission limit, then the facility would be considered to have achieved the 

emission limit. We recommend that, during the test, the facility monitor and record 

relevant control device and capture system operating parameters and use the recorded 

values to establish operating limits for those parameters. We recommend that the facility 

monitor the operating parameters for the control device and emission capture system and 

maintain the parameters within the established operating limits. All resins and gel coats 

used in these controlled operations would also need to meet the recommended nonmonomer VOC content limit of 5 percent. 

B. Recommended Option for Filled Resins

Some facilities use resins to which fillers are added to achieve certain physical 

properties, particularly for building molds. The resins to which the filler is added have 

higher initial monomer VOC content than standard production or tooling resins, but the 

addition of the filler lowers the monomer VOC emission rate from the filled resin. We 

recommend the use of the following equation to adjust the emission rate for filled resins 

under all three options recommended above for limiting monomer VOC emissions from 

resins and gel coats. If a facility is using a filled production resin or filled tooling resin, it 

would calculate the emission rate for the filled material on an as-applied basis using 

Equation 5. 

Equation 5: 

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( )

100

%100 Filler

F PVPV U

−

×= 

Where: 

 PVF = The as-applied monomer VOC emission rate for the filled 

production resin or tooling resin, kilograms monomer VOC per 

megagram of filled material. 

 PVu = The monomer VOC emission rate for the neat (unfilled) resin, 

before filler is added, as calculated using the formulas in Table 4 of 

this CTG. 

 % Filler = The weight-percent of filler in the as-applied filled resin system. 

 If the filled resin is used as a production resin, we recommend that the value of 

PVF calculated by Equation 5 not exceed 46 kilograms of monomer VOC per megagram 

of filled resin applied. If the filled resin is used as a tooling resin, we recommend that the 

value of PVF calculated by Equation 5 not exceed 54 kilograms of monomer VOC per 

megagram of filled resin applied. If the facility is including a filled resin in the emissions 

averaging procedure, we recommend that the facility use the value of PVF calculated 

using Equation 5 for the value of PVi

 in Equation 4 of this CTG. All filled resins would 

also need to meet the recommended non-monomer VOC content limit of 5 percent, based 

on the unfilled resin. 

C. Work Practices for Resin and Gel Coat Mixing Containers

 In addition to the recommended monomer and non-monomer VOC limits for gel 

coats and resins described above, this CTG recommends that all resin and gel coat mixing 

containers with a capacity equal to or greater than 208 liters (55 gallons), including those 

used for on-site mixing of putties and polyputties, have a cover with no visible gaps in 

place at all times. We do not recommend the use of covers for smaller containers 

because they are typically only used for small hand application operations that require an 

open container. Also, this work practice would not apply when material is being 

manually added to or removed from a container, or when mixing or pumping equipment 

is being placed in or removed from a container. Although monomer and non-monomer 

VOC emission reductions achieved by implementing this work practice may not be 

quantifiable, we have concluded that they are beneficial to the overall goal of reducing 

VOC emissions. 

D. VOC Content and Vapor Pressure Limits for Cleaning Materials

 Cleaning solvents used to remove resin and gel coat residue from application 

equipment are a potential source of significant VOC emissions. However, low-VOC and 

low vapor pressure cleaning materials that can be used for cleaning boat manufacturing 

application equipment are readily available. These materials include aqueous emulsifiers 

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that have very low VOC contents, and also organic solvents, such as dibasic esters 

(DBE), that have very low vapor pressures. Therefore, we are recommending that VOC 

cleaning solvents for routine application equipment cleaning contain no more than 5 

percent VOC, by weight, or have a composite vapor pressure of no more than 0.50 mm 

Hg at 68 oF. 

 These recommended limits for cleaning materials are based on the properties of 

water-based emulsifiers and dibasic esters that are used as alternatives to conventional 

cleaning solvents, and are the basis for the equipment cleaning requirements in the 2001 

NESHAP for Boat Manufacturing. Therefore, the same cleaning materials used to 

comply with the 2001 NESHAP will meet the VOC content and vapor pressure limits 

recommended in this CTG for cleaning materials. Based on the implementation of these 

measures by all major source fiberglass boat manufacturers, we believe that these control 

measures are technically and economically feasible for reducing VOC emissions from 

these cleaning materials and have therefore included them as our recommendations in the 

CTG. 

 Occasionally through operator error or equipment malfunctions, resin or gel coat 

is accidentally allowed to cure inside application equipment. To remove the cured resin 

or gel coat, the equipment is typically soaked in a container of methylene chloride to 

dissolve the cured material. Boat manufacturing facilities usually maintain a small 

amount (e.g., a few gallons) of methylene chloride on site for these situations. Methylene 

chloride is not a VOC. We recommend that only non-VOC solvents be used to remove 

cured resin and gel coat from application equipment. 

VII. Cost Effectiveness of Recommended Control Options

Based on the 2002 NEI database, we estimate that there are 223 fiberglass boat 

manufacturing facilities in the U.S. Using the April 2004 ozone nonattainment 

designations, 91 of these facilities are in ozone nonattainment areas. Based on the 2002 

NEI VOC emissions data, we estimated that 67 of the 91 facilities in ozone 

nonattainment areas emitted VOC at or above the recommended 6.8-kg/day (15-lb/day) 

VOC emissions applicability threshold. These 67 facilities, in aggregate, emit about 

1,452 Megagrams per year (Mg/yr) (1,601 tons per year (tpy)) of VOC per year, or an 

average of about 22 Mg/yr (24 tpy) of VOC per facility. 

The CTG recommends the use of low-VOC content (monomer and non-monomer 

VOC) resin and gel coats with specified application methods. The CTG recommends the 

use of covers on mixing containers to further reduce VOC emissions from gel coats and 

resins. The CTG also recommends the use of low-VOC and low vapor pressure cleaning 

materials. Because the recommendations in this CTG are based on the 2001 NESHAP 

for boat manufacturing, those facilities that are major sources of HAP are already 

complying with the 2001 NESHAP and have already adopted these control measures. 

Therefore, we do not anticipate additional VOC emission reductions from these major 

source facilities. 

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Because the 2001 NESHAP does not apply to area sources (i.e. sources that are 

not major sources of HAP), area source fiberglass boat manufacturing facilities are not 

currently required to implement the measures provided in the 2001 NESHAP and 

recommended in the CTG. We estimate that 23 area source fiberglass boat 

manufacturing facilities are located in ozone nonattainment areas and meet the 

applicability threshold recommended in the CTG, and that these facilities emit, in 

aggregate 104 Mg/yr (115 tpy) of VOC. We estimate that implementation of the 

recommended measures in the CTG would reduce VOC emissions at these 23 facilities 

by about 37 Mg/yr (40 tpy). 

For implementing the 2001 NESHAP, the EPA estimated a cost of $3,600 per ton 

of HAP reduced, in 2001 dollars, or about $4,200 in 2007 dollars. Nearly all of the HAP 

that are reduced by the NESHAP are styrene and MMA, and styrene and MMA also 

account for nearly all of the VOC emitted from the processes addressed by the 

recommendations in this CTG. Therefore, we expect that the cost to reduce HAP and 

VOC are nearly equal. 

 

 However, we expect that the cost of reducing VOC through the measures 

recommended in this CTG would be substantially lower than the cost of reducing HAP 

through the 2001 NESHAP for several reasons. First, the NESHAP is now fully 

implemented at major sources of HAP, and resin, gel coat, and cleaning materials that are 

compliant with the 2001 NESHAP are readily available to all sizes of facilities. Second, 

the industry has experienced a shift to non-atomized resin application methods that are 

required to comply with the 2001 NESHAP. This shift has occurred at all sizes of 

facilities because of the productivity and economic benefits of using non-atomizing 

methods over conventional atomizing methods. Therefore, with respect to those facilities 

that are not subject to the 2001 NESHAP, we expect that most, if not all, are already 

using the materials and methods recommended by this CTG. We therefore expect that 

these facilities would incur little, if any, increased costs if required by a State RACT rule 

to implement the approaches recommended in this CTG. We estimate that the total 

annual cost for the 23 facilities to implement the recommended measures in this CTG 

would be substantially less than $168,000 in 2007 dollars. 

APPENDIX E: CTG SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT August 18, 2011 E - 42 Final Staff Report with Appendices 

for Proposed Amendments to Rule 4684
35

VIII. References

Project Summary. Assessment of VOC Emissions from Fiberglass Boat Manufacturing. 

Publication No. EPA/600/S2-90/019. U.S. Environmental Protection Agency, Research 

Triangle Park, NC. June 1990. 

40 CFR Part 63, Subpart VVVV - National Emission Standards for Hazardous Air 

Pollutants for Boat Manufacturing. §§63.5680 – 63.5776. 

Economic Impact Analysis of the Boat Manufacturing NESHAP. U.S. EPA Office of Air 

Quality Planning and Standards. Research Triangle Park, NC 27711. EPA Publication 

No. EPA/452/R-01-011. June 2001. 

Bay Area (California) Air Quality Management District Regulation 8, Organic 

Compounds, Rule 50, Polyester Resin Operations. Adopted June 15, 1994. 

San Diego (California) Air Pollution Control District Rule 67-12. Polyester Resin 

Operations. Amended May 15,1996. 

Santa Barbara (California) Air Pollution Control District Rule 349. Polyester Resin 

Operations. Adopted April 27,1993. 

South Coast (California) Air Quality Management District Regulation XI, Source 

Specific Standards, Rule 1162, Polyester Resin Operations. Amended July 8, 2005. 

South Coast (California) Air Quality Management District Method 312-91, 

Determination of Percent Monomer in Polyester Resins, revised April 1996 

Code of Maryland Administrative Regulations (COMAR) 26.11.19.26. Control of 

Volatile Organic Compound Emissions from Reinforced Plastic Manufacturing. 

Approved as part of Maryland SIP on August 19, 1999. 

Puget Sound (Washington) Clean Air Agency, Regulation 2, Section 3.08, Polyester, 

Vinylester, Gelcoat, and Resin Operations. Revised December 9, 1993. 

Indiana Administrative Code, 326 IAC 8-1-6. Volatile Organic Compound Rules; New 

facilities, general reduction requirements. Amended May 26, 2006.

Illinois Rule 218, Subpart CC. Organic Material Emission Standards and Limitations for 

the Chicago Area. Subpart CC: Polyester Resin Product Manufacturing Process. 

Effective January 24, 1994. 

APPENDIX E: CTG SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT August 18, 2011 E - 43 Final Staff Report with Appendices 

for Proposed Amendments to Rule 4684
SAN JOAQUIN VALLEY UNIFIED AIR POLLUTION CONTROL DISTRICT 

APPENDIX E: CTG August 18, 2011 

Final Staff Report with Appendices 

 For Proposed Amendments to Rule 4684

E-44

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