RULE 4684 POLYESTER RESIN OPERATIONS (Adopted May 19, 1994; Amended 

December 20, 2001; Amended September 20, 2007; Amended September 17, 

2009; Amended August 18, 2011) 

1.0 Purpose 

The purpose of this rule is to reduce emissions of volatile organic compounds (VOC) 

from polyester resin operations, fiberglass boat manufacturing operations and the 

organic solvent cleaning, and the storage and disposal of solvents and waste solvent 

materials associated with such operations. 

2.0 Applicability 

The provisions of this rule apply to commercial and industrial polyester resin 

operations, fiberglass boat manufacturing operations, and to the organic solvent 

cleaning, and the storage and disposal of all solvents and waste solvent materials 

associated with such operations. 

3.0 Definitions 

The following definitions apply for the purpose of this rule. 

3.1 Air Pollution Control Officer (APCO): as defined in Rule 1020 (Definitions). 

3.2 Application Equipment: a device, including, but not limited to, a spray gun, 

brush, and roller, used to apply adhesives, coatings, or inks. 

3.3 ARB: California Air Resources Board. 

3.4 Assembly Adhesive: a chemical material used in joining fiberglass, metal, 

foam, or wood parts to another to form a temporary or permanently bonded 

assembly. Assembly adhesives include, but are not limited to, methacrylate 

adhesives and putties made from polyester or vinylester resin mixed with inert 

filler or fibers. 

3.5 ASTM: American Society of Testing and Materials International. 

3.6 Atomized Resin Application: a resin application technology in which the resin 

leaves the application equipment and breaks into droplets or an aerosol as it 

travels from the application equipment to the surface of the part. Atomized 

resin application includes, but is not limited to, resin spray guns and resin 

chopper spray guns. 
 

 
  

3.7 Bench Scale Project: a project (other than at a research and development 

facility) that is operated on a small scale, such as one capable of being located 

on a laboratory bench top. 

3.8 Catalyst: a substance that is added to resin to initiate or promote 

polymerization. 

3.9 CFR: Code of Federal Regulations. 

3.10 Cleaning Materials: materials including, but not limited to, materials used for 

cleaning hands, tools, molds, application equipment, and work areas. 

3.11 Clear Gel Coat: a gel coat that is clear or translucent so that underlying colors 

are visible. Clear gel coat is used to manufacture parts for sale. Clear gel coat 

does not include tooling gel coat used to build or repair molds. 

3.12 Closed Molding Process: a 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 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 vacuum-assisted 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 gel coat or skin coat layer by 

conventional open molding prior to a closed molding process are not closed 

molding. 

3.13 Coating: a material applied onto or impregnated into a substrate for protective, 

decorative, or functional purposes. Such materials include, but are not limited 

to, paints, varnishes, sealers, and stains. 

3.14 Corrosion–Resistant Material: a polyester resin material used to make products 

for corrosion resistant applications such as tooling, fuel or chemical tanks, boat 

hulls, pools and outdoor spas. 

3.15 Cure: to polymerize, i.e., to transform from a liquid to a solid state or semisolid state to achieve desired physical properties for the product, including 

hardness. 

3.16 Cured Coating: a coating that is dry to the touch. 
 

 
  

3.17 Degreaser: a tank, tray, drum or other container in which objects to be cleaned 

are exposed to a solvent or solvent vapor in order to remove contaminants. The 

objects to be cleaned include, but are not limited to, parts, products, tools, 

machinery, and equipment. An enclosed spray application equipment cleaning 

system is not a degreaser. 

3.18 Dissolver: an organic solvent that is added to an adhesive, coating, or ink in 

order to melt or to liquefy solid particles. 

3.19 EPA: United States Environmental Protection Agency. 

3.20 Fiberglass Boat: a vessel in which either the hull or deck is built from a 

composite material consisting of thermosetting resin matrix reinforced with 

fibers of glass, carbon, or other material. 

3.21 Fiberglass Boat Manufacturing: facilities that manufacture hulls or decks of 

boats from fiberglass, or build molds to make fiberglass boat hulls or decks. 

Facilities that manufacture solely parts of boats (such as hatches, seats, or 

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

fiberglass or build molds to make fiberglass boats or hulls are not considered 

fiberglass boat manufacturing. A facility that manufactures hulls or decks, or 

molds for hulls or decks, and other fiberglass boat parts, including small parts 

such as hatches, seats, and lockers, is considered fiberglass boat manufacturing. 

Fiberglass boat manufacturing operations include 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. 

3.22 Filament Application: a method of applying resin to an open mold that involves 

feeding reinforcement fibers through a resin bath and winding the resinimpregnated fibers on a rotating mandrel. 

3.23 Filled Polyester Resin Material: a material formulated by adding compatible 

filler(s) to polyester resin material(s). 

3.24 Filler: a finely divided inert (non-VOC) material, which may be added to the 

resin to enhance its mechanical properties and extend its volume. Resin fillers 

include, but are not limited to, silica, carbon black, talc, mica and calcium 

carbonate. 

3.25 Fire Retardant Material: a polyester resin material used to make products that 

are resistant to flame or fire. 
 

 
 
 

3.26 Fluid Impingement Technology: a spray gun that produces an expanding nonmisting curtain of liquid by the impingement of low-pressure uninterrupted 

liquid streams. 

3.27 Gel Coat: a polyester resin topcoat that provides a cosmetic enhancement and 

improves resistance to degradation from environmental exposure. 

3.28 Grams of VOC per liter of material: grams VOC per liter of material is 

determined as follows: 

Grams VOC per liter of material = (Ws - Ww - Wes) / Vm

Where: 

Ws = weight of all volatile compounds, in grams 

Ww = weight of water, in grams 

Wes = weight of exempt solvents, in grams 

Vm = volume of the material, in liters 

3.29 High-Strength Material: polyester resins which have a casting tensile strength 

of 10,000 psi or more and which are used primarily for manufacturing high 

performance boats and skis. 

3.30 High-Volume, Low-Pressure (HVLP) Spray Equipment: equipment used to 

apply materials by means of a spray gun which is designed and intended to be 

operated, and which is operated, between 0.1 and 10.0 psig of air atomizing 

pressure, measured dynamically at the center of the air cap and the air horns. 

3.31 Lamination Resin: an orthophthalate, isophthalate and dicyclopentadiene 

(DCPD) resin which is used in composite system made of layers of 

reinforcement fibers and resins, such as in boat fabrication. 

3.32 Liquid Leak: a visible solvent leak from a container at a rate of more than three 

drops per minute, or a visible liquid mist. 

3.33 Maintenance Cleaning: the cleaning of tools, forms, molds, jigs, machinery, 

and equipment (except coating application equipment, ink application 

equipment, or adhesive application equipment), and the cleaning of work areas 

where maintenance or manufacturing occurs. 

3.34 Manual Application: the application of resin to an open mold using a hand layup technique. Components of successive plies of resin-impregnated 

reinforcement fibers are applied using hand tools such as brushes and rollers. 
 

 
  

3.35 Manufacturing Process: the process of making goods or articles by hand or by 

machine. 

3.36 Marble Resin: an orthophthalate and modified acrylic isophthalate resin, which 

is designed for the fabrication of cast products, such as vanities. 

3.37 Mold: the cavity or surface into or on which gel coat, resin, and fibers are 

placed and from which finished fiberglass parts take their form. 

3.38 Monomer: an organic compound, such as styrene, that reacts with unsaturated 

polyester resins to form a cured polyester resin. 

3.39 Month: a calendar month. 

3.40 Neat Resin: a resin to which no filler has been added. 

3.41 Non-Absorbent Container: a container made of non-porous material that does 

not allow the migration of solvents through it. 

3.42 Non-Atomized Resin Application: an application technology in which the resin 

is not broken into droplets or an aerosol as it travels from the application 

equipment to the surface of the part. Non-atomized resin application technology 

includes, but is not limited to, non-atomizing spray guns, flowcoaters, chopper 

flowcoaters, pressure fed resin rollers, resin impregnators, or fluid impingement 

technology. 

3.43 Non-Atomized Solvent Flow: solvents in the form of a liquid stream without 

the introduction of any propellant. 

3.44 Non-Atomizing Spray Gun: a spray gun from which the resin flows in a steady 

and observable coherent flow, with no droplets formed in the area that is within 

the first three (3) inches of the applicator orifice. Droplets may form in the area 

greater than three (3) inches from the applicator orifice. 

3.45 Non-Leaking Container: a container without a liquid leak. 

3.46 Normal Business Hours: Monday through Friday, 8:00 am to 5:00 pm. 

3.47 Open Molding Resin and Gel Coat Process: a process in which the reinforcing 

fibers and resin are placed in the mold and are open to the surrounding air while 

the reinforcing fibers are saturated with resin. For the purpose of this rule, 

open molding includes operations in which a vacuum bag or similar cover is 

used to compress the uncured laminate to remove bubbles or excess resin, or to 

achieve a bond between core material and a laminate. 
 

 
  

3.48 Organic Solvent: the same as “Solvent.” 

3.49 Organic Solvent Cleaning: as defined in Rule 4663 (Organic Solvent Cleaning, 

Storage, and Disposal). 

3.50 Pigmented Gel Coat: opaque gel coat used to manufacture parts for sale. 

Pigmented gel coat does not include tooling gel coat used to build or repair 

molds. 

3.51 Polyester Resin Materials: materials including, but not limited to: unsaturated 

polyester resins such as isophthalic, orthophthalic, halogenated, Bisphenol-A, 

vinyl-ester, or furan resins; cross-linking agents; catalysts, gel coats, inhibitors, 

accelerators, promoters, and any other materials used in polyester resin 

operations. 

3.52 Polyester Resin Operations: methods used for the production or rework of 

products by mixing, pouring, hand layup, impregnating, injecting, forming, 

winding, spraying, and/or curing with fiberglass, fillers, or any other 

reinforcement materials and associated cleanup. 

3.53 Polymer: a chemical compound comprised of a large number of chemical units 

and which is formed by chemical linking of monomers. 

3.54 Production Resin: a general purpose resin material that is not especially 

corrosion resistant, fire retardant, high strength, or gel coats. 

3.55 Propellant: any gas, including air, in a pressure container for expelling the 

contents when the pressure is released. 

3.56 Repair: the process of returning a damaged object or an object not operating 

properly to good condition. 

3.57 Repair Cleaning: a solvent cleaning operation or activity carried out during a 

repair. 

3.58 Research and Development: a facility or portion thereof used to further the 

development of useful materials, devices, systems, or methods, including, but 

not limited to, design, development, and improvement of prototypes and 

processes. Research and development does not include the manufacturing 

process itself. 

3.59 Resin: a class of organic polymers of natural or synthetic origin used in 

reinforced products to surround and hold fibers or filler particles, and is solid or 

semisolid in the cured state. 
 

 
  

3.60 Resin and Gel Coat Operation: an operation in which resin or gel coat, 

including the mixing of putties or polyputties, is combined with additives that 

include, but are not limited to, fillers, promoters, or catalysts. 

3.61 SCAQMD: South Coast Air Quality Management District. 

3.62 Skin Coat: a layer of resin and fibers applied over gel coat to protect the gel 

coat from being deformed by the next laminate layers. 

3.63 Small Job: minor resin or gel coat application project which requires only a 

very limited amount of materials. Total material use for all small jobs at a 

facility shall not exceed two (2) gallons a day. 

3.64 Solid Surface Resin: a resin, which is used, without gel coats, to fabricate 

homogenous solid surface products. 

3.65 Solvent: as defined in Rule 4663 (Organic Solvent Cleaning, Storage, and 

Disposal). 

3.66 Specialty Gel Coat: a gel coat which is used in conjunction with fire retardant, 

corrosion resistant or high-strength materials. 

3.67 Specialty Resin: a halogenated, furan, bisphenol A, vinyl-ester, or isophthalic 

resin used to make products for exposure to one or more of the following 

extreme environmental conditions: acute or chronic exposure to corrosive 

agents, caustic agents, acidic agents, or flame. 

3.68 Stationary Source: as defined in Rule 2201 (New and Modified Stationary 

Source Review Rule). 

3.69 Tooling Gel Coat: the gel coat used to build or repair molds (also known as 

tools) or prototypes (also known as plugs) from which the molds will be made. 

3.70 Tooling Resin: the resins used to build or repair molds (also known as tools) or 

prototypes (also know as plugs) from which the molds will be made. 

3.71 Touch-up: The application of resin or gel coat to correct minor cosmetic 

imperfections that occur during fabrication or field installations. 

3.72 Tub/Shower Resin: a dicyclopentadiene (DCPD) resin, along with 

orthophthalate and isophthalate resins, which are used to fabricate bathware 

products. 

3.73 Vapor Suppressant: a substance added to resin to minimize the transfer of 

monomer vapor into the atmosphere. 
 

 
  

3.74 Vinylester Resin: a thermosetting resin containing esters of acrylic or 

methacrylic acids having a double-bond and ester linkage sites at the end of the 

resin molecules. 

3.75 Volatile Organic Compound (VOC): as defined in Rule 1020 (Definitions). 

3.76 Waste Materials: materials including but not limited to paper or cloth used for 

cleaning operations, waste resins, or spent cleaning materials. 

4.0 Exemptions 

4.1 Except for fiberglass boat manufacturing operations, the provisions of this rule, 

other than the recordkeeping requirements of Section 6.1, shall not apply to any 

polyester resin operation provided the volume of polyester resin materials used 

is less than 20 gallons per month. 

4.2 For fiberglass boat manufacturing, production resins (including skin coats) that 

must meet the specifications for use in military vessels or must be approved by 

the U.S. Coast Guard for use in construction of lifeboats, rescue boats, and 

other life-saving appliances approved under 40 CFR subchapter Q, or to the 

construction of small passenger vessels regulated by 46 CFR subchapter T are 

exempt from the requirements of Section 5.2.2. Production resins that meet 

these criteria shall be applied with nonatomizing resin application equipment. 

4.3 The solvent cleaning provisions of Section 5.3 Table 4 shall not apply to the 

following applications: 

4.3.1 Cleaning of solar cells, laser hardware, scientific instruments, or high 

precision optics. 

4.3.2 Cleaning in laboratory tests and analyses, or bench scale or research and 

development projects. 

5.0 Requirements 

 5.1 Polyester Resin Operation, except for Fiberglass Boat Manufacturing subject to 

Section 5.2.2. 

5.1.1 An operator of a polyester resin operation shall comply with one of the 

following process or control requirements: 

5.1.1.1 Prior to January 1, 2013, use low-VOC polyester resins with 

the following monomer content: Low VOC resins, except for 

specialty resins and gel coats, containing no more than 35% 

monomer by weight. Low VOC pigmented gel coats containing 
 

 
  

no more than 45% monomer by weight. Low VOC specialty 

resins and clear gel coats containing no more than 50% 

monomer by weight; or comply with Section 5.1.1.3, 5.1.1.4, 

or 5.1.1.5. 

5.1.1.2 On and after January 1, 2013, use materials in an open molding 

process that comply with the weighted average monomer VOC 

content limits in Table 1. In addition to complying with Table 

1 limits, the non-monomer VOC content of each resin and gel 

coat shall not contain more than 5 percent by weight of the 

resin or gel coat; or comply with Section 5.1.1.3, 5.1.1.4, or 

5.1.1.5. 

Table 1 Compliant Materials Weighted Average Monomer VOC Content 

for Open Molding Resin and Gel Coat 

Material Weight Percent Limit on and after 

January 1, 2013 

a. General Purpose Resin 

 - Marble Resin 10% or 

32%, as supplied, with no fillers 

 - Solid Surface Resin 17% 

 - Tub/Shower Resin 24% or 

35%, as supplied, with no fillers 

 - Lamination Resin 31% or 

35%, as supplied, with no fillers 

b. Tooling Resin 

 - Atomized (spray) 30% 

 - Non-atomized 39% 

c. Specialty Resin 

 - Fire Retardant Resin 38% 

 - High Strength Materials 40% 

 - Corrosion Resistant Resin 48% 

d. All Other Resin 35% 

e. Tooling Gel Coat 40% 

f. Pigmented Gel Coat 

 - White and Off White 30% 

 - Non-White 37% 

 - Primer 28% 

g. Clear Gel Coat 

 - Marble Resin 40% 

 - Other Resin 44% 

h. Specialty Gel Coat 48% 
 

 
  

5.1.1.3 Use resin containing a vapor suppressant, such that the weight 

loss from the VOC emissions does not exceed 50 grams per 

square meter of exposed surface during resin polymerization; or 

5.1.1.4 Use a closed-mold system; or 

5.1.1.5 Install and operate a VOC emission control system which meets 

all of the requirements of Sections 5.1.1.5.1 through 5.1.1.5.3 

during periods of emission producing activities. 

5.1.1.5.1 The VOC emission control system shall be 

approved, in writing, by the APCO. 

5.1.1.5.2 The VOC emission control system shall have an 

overall capture and control efficiency of at least 90 

percent by weight, demonstrated using the applicable 

test method(s) in Section 6.2. 

5.1.1.5.3 The VOC emission control system shall reduce VOC 

emissions, at all times, to a level that is not greater 

than the emission which would have been achieved 

through the use of compliant materials, compliant 

equipment, or compliant work practices, as 

applicable. The following equation shall be used to 

determine if the minimum required overall capture 

and control efficiency of an emission control system 

is at an equivalent or greater level of VOC reduction 

as would be achieved using compliant materials, 

equipment, or work practices: 

( )

( ) x 100

-1 VOC c / D

-1 VOC / D

 x 

VOC

VOC CE = -1

LW c

LWn,Max n,Max

LWn,Max

LWc

































Where: 

CE = Minimum Required Control Efficiency 

specified in Section 5.1.1.5.2 in percent. 

VOCLWc = VOC content of applicable resin, gel coat, or 

solvent of Rule 4684, less water and less 

exempt compounds. 

VOCLWn,Max = Maximum VOC content of resin, gel coat, or 

solvent, used in conjunction with a control 

device, less water and less exempt compounds. 
 

 
  

Dn,Max = Density of the noncompliant resin, gel coat, or 

solvent, containing the maximum VOC content 

of the multi-component material. 

Dc = Density of corresponding resin, gel coat or 

solvent, used in the compliant resin, gel coat, 

or solvent. 

5.1.1.6 Resins and gel coats used for touch up, repair, or small jobs, 

may have a monomer content limit up to 10% more than the 

applicable limit set forth in Table 1. Such resins or gel coats 

shall only be applied by a hand-held atomized spray gun which 

has a container for the resin or gel coat as part of the gun. 

Resins or gels applied by another method shall comply with the 

applicable limit in Table 1. Total material use for all small jobs 

at a facility shall not exceed two (2) gallons a day. 

5.1.2 Spray application of polyester resin shall only be performed using 

airless, air assisted airless, high-volume, low-pressure (HVLP) spray 

equipment, or electrostatic spray equipment. 

5.1.2.1 High-Volume, Low-Pressure (HVLP) spray equipment shall be 

operated in accordance with the manufacturer's 

recommendations. 

5.1.2.2 For HVLP spray guns manufactured prior to January 1, 1996, 

the end user shall demonstrate that the gun meets HVLP spray 

equipment standards. Satisfactory proof will be either in the 

form of manufacturer's published technical material or by a 

demonstration using a certified air pressure tip gauge, 

measuring the air atomizing pressure dynamically at the center 

of the air cap and at the air horns. 

5.1.2.3 A person shall not sell or offer for sale for use within the 

District any HVLP spray gun without a permanent marking 

denoting the maximum inlet air pressure in psig at which the 

gun will operate within the parameters specified in Section 3.0. 

5.1.3 In lieu of complying with the applicable requirements of 5.1.2, an 

operator may install and maintain a VOC emission control system that 

meets the requirements of Section 5.1.1.5 around the coating application 

operation. 
 

 
  

 5.2 Fiberglass Boat Manufacturing Operation 

 5.2.1 Requirements for Closed Molding Process 

 

 An operator of a fiberglass boat manufacturing facility who uses a closed 

molding process, as defined in Section 3.0, shall comply with the 

applicable requirements of Sections 5.1, 5.3, 5.4, and 6.0. 

 

 5.2.2 Requirements for Open Molding Process 

 5.2.2.1 An operator of a fiberglass boat manufacturing facility who 

uses an open molding process, as defined in Section 3.0, and 

whose total actual VOC emissions from all fiberglass boat 

manufacturing operations, including related solvent cleaning 

activities, at a stationary source are equal to or greater than 

2.7 tons of VOC per 12-month rolling period, before

consideration of controls, shall comply with at least one of the 

Compliance Options in Section 5.2.2.4 through 5.2.2.6, and 

the applicable requirements of Sections 5.3, 5.4, and 6.0. 

 5.2.2.2 An operator subject to Section 5.2.2.1 shall comply with the 

applicable recordkeeping requirements of Section 6.1 and 

calculate the fiberglass boat manufacturing facility emissions to 

demonstrate if the VOC emissions from all fiberglass boat 

manufacturing operations, including related solvent cleaning 

activities, at a stationary source are equal to or greater than 

2.7 tons of VOC per 12-month rolling period, before

consideration of controls. 

5.2.2.3 An operator of an open molding process whose total actual 

VOC emissions from all fiberglass boat manufacturing 

operations, including related solvent cleaning activities, at a 

stationary source are less than 2.7 tons of VOC per 12-month 

rolling period, before consideration of controls, shall comply 

with the applicable requirements of Sections 5.1, 5.3, 5.4, 

and 6.0. The operator shall comply with the applicable 

recordkeeping requirements of Section 6.1 and calculate the 

fiberglass boat manufacturing facility emissions to demonstrate 

if the VOC emissions from all open molding fiberglass boat 

manufacturing operations, including related cleaning activities 

are less than 2.7 tons of VOC per 12-month rolling period. 

 
 

 
  

 5.2.2.4 Requirements for Compliant Materials 

 

 5.2.2.4.1 An operator subject to Section 5.2.2.1 shall not use 

materials in any open molding process that exceed 

the weighted average monomer VOC content limits 

in Table 2. In addition to complying with Table 2 

limits, the non-monomer VOC content of each 

resin and gel coat shall not contain more than 5 

percent by weight of the resin or gel coat. 

Table 2 Compliant Materials Monomer VOC Content 

for Open Molding Resin and Gel Coat for Fiberglass Boat Manufacturing Operation 

Material Application Method 

Weighted Average Monomer 

VOC content 

(weight percent) limit 

Production Resin Atomized (spray) 28% 

Production Resin Non-atomized 35% 

Pigmented Gel Coat Any method 33% 

Clear Gel Coat Any method 48% 

Tooling Resin Atomized 30% 

Tooling Resin Non-atomized 39% 

Tooling Gel Coat Any method 40% 

 

 5.2.2.4.2 The weighted average monomer VOC content shall 

be determined based on a 12-month rolling 

average. The operator shall use Equation 1 to 

determine weighted average monomer content for a 

particular open molding resin or gel coat material.

Equation 1: 

 Weighted Average Monomer VOC Content = 

∑

∑

=

=

n

i 1

)i(

n

i 1

)i( )i(

(M )

(M VOC )

 

 Where: 

M(i) = Mass of open molding resin or gel coat i used in the past 12 months 

in an operation, megagrams. 

 

VOC(i) = 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. 

 

 5.2.2.5 Requirements for Emissions Averaging Option 

 5.2.2.5.1 In lieu of complying with the requirements of 

Section 5.2.2.4, an operator that is subject to 

Section 5.2.2.1 may comply by meeting a facilityspecific monomer VOC mass emission limit (12-

month rolling average) that is determined using 

Equation 2, provided all resins and gel coats 

included in this option do not exceed 5 percent by 

weight non-monomer VOC content. 

 5.2.2.5.2 At the end of the first 12-month averaging period 

and at the end of every subsequent month, the 

operator shall 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. The operator shall include in 

Equation 2 and Equation 3 the terms for only those 

operations and materials included in the average. 

 

 5.2.2.5.3 For those materials that are not included in the 

emissions average, the facility would resort to one

of the other two options for limiting monomer and 

non-monomer VOC emissions from resin and gel 

coats. 

 

 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 

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 pursuant to Section 

4.2, in megagrams. 
 

 
  

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

excluding any materials that are exempt pursuant to Section 

4.2, in megagrams. 

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

any materials that are exempt, in megagrams. 

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

any materials that are exempt pursuant to Section 4.2, in 

megagrams. 

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

excluding any materials that are exempt pursuant to Section 

4.2, in megagrams. 

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, in kilograms. 

 

 PVR = Weighted-average monomer VOC emission rate for 

production resin used in the past 12 months, in 

kilograms per megagrams. 

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

megagrams. 

 

 PVPG = Weighted-average monomer VOC emission rate for 

pigmented gel coat used in the past 12 months, in 

kilograms per megagrams. 

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

in megagrams. 

 PVCG = Weighted-average monomer VOC emission rate for 

clear gel coat used in the past 12 months, in kilograms 

per megagrams. 
 

 
  

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

megagrams 

 PVTR = Weighted-average monomer VOC emission rate for 

tooling resin used in the past 12 months, in kilograms 

per megagrams. 

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

megagrams. 

 PVTG = Weighted-average monomer VOC emission rate for 

tooling gel coat used in the past 12 months, in kilograms 

per megagrams. 

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

megagrams. 

 

 5.2.2.5.4 For purposes of Equation 3, the operator shall 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: 

 PVOP = 

∑

∑

=

=

n

i 1

n

i 1

(Mi)

(Mi PVi)

 

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, in megagrams. 

 n = Number of different open molding resins and gel coats used with 

the operation in the past 12 months. 
 

 
  

 PVi = The monomer VOC emission rate for resin and gel coat i used 

within an operation in the past 12 months, in kilograms of 

monomer VOC per megagram of material applied. Use Table 3 to 

compute PVi. 

Table 3 Monomer VOC Emission Rate Formulas for Open Molding 

for Fiberglass Boat Manufacturing Operation 

Material Application Method Formula to calculate monomer 

VOC emission rate* 

Production resin, 

Tooling resin 

Atomized 0.014 x (Resin VOC%)2.425

Atomized, plus vacuum 

bagging with roll-out 0.01185 x (Resin VOC%)2.425

Atomized, plus vacuum 

bagging without roll-out 0.009454 x (Resin VOC%)2.425

Non-atomized 0.014 x (Resin VOC%)2.275

Non-atomized, plus vacuum 

bagging with roll-out 0.0110 x (Resin VOC%)2.275

Non-atomized, plus vacuum 

bagging without roll-out 0.0076 x (Resin VOC%)2.275

Pigmented gel coat, clear 

gel coat, tooling gel coat All methods 0.445 x (Gel coat VOC%)1.675

* The formulas in Table 3 calculate monomer VOC emissions in kilograms of monomer 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 the resin and fabric. VOC% = monomer VOC content as supplied, expressed as a 

weight-percent value between 0 and 100%. 

5.2.2.6 Requirements for Add-on VOC Control System Option 

 5.2.2.6.1 In lieu of complying with the requirements of 

Compliant Materials Option in Section 5.2.2.4 or 

the requirements of Emissions Averaging Option in 

Section 5.2.2.5, an operator may choose to use an 

APCO-approved add-on control equipment to meet 

the emission limit determined by Equation 2 

above. However, instead of using the mass of 

each material used over the past 12 months in 

Equation 2, the operator shall use the mass of each

material used during control device performance 

source testing in Equation 2 to determine the 

emission limit (in kilograms of monomer VOC) 

that is applicable during the source testing. If the 
 

 
  

measured emissions at the outlet of the control 

device (in kilogram of monomer VOC) are less 

than the emission limit, then the control device 

shall be considered to have achieved the emission 

limit, and provided the control device also meets 

the requirements of Sections 5.1.1.5.1 through 

5.1.1.5.3. 

 5.2.2.6.2 All resins and gel coats used during add-on VOC 

controlled operations shall not exceed 5 percent by

weight non-monomer VOC content limit. 

 5.2.2.6.3 The operator shall monitor and record relevant 

control device and capture system operating 

parameters such as temperature, pressure, and 

flow rate, and use the recorded values to establish

operating limits for the emission control device and 

capture system, and maintain such parameters 

within the established operating limits. 

5.2.2.7 Requirements for Filled Resins 

 

 5.2.2.7.1 An operator who uses resins to which fillers are 

added shall use Equation 5 to adjust the emission 

rate for filled resins under all three options 

specified in Section 5.2.2.4 through Section 

5.2.2.6. If an operator uses a filled production 

resin or filled tooling resin, the operator shall 

calculate the emission rate for filled material on an 

as-applied basis using Equation 5. 

 5.2.2.7.2 All filled resins used shall not exceed 5 percent by 

weight non-monomer VOC content limit. 

 

 5.2.2.7.3 If the filled resin is used as a production resin, the 

value of PVF calculated by Equation 5 shall not 

exceed 46 kilograms of monomer VOC per 

megagram of filled resin applied. 

 5.2.2.7.4 If the filled resin is used as a tooling resin, the 

value of PVF calculated by Equation 5 shall not 

exceed 54 kilograms of monomer VOC per 

megagram of filled resin applied. 
 

 
  

 5.2.2.7.5 If the operator is including a filled resin in the 

emissions averaging option procedure, the operator 

shall use the value of PVF calculated using 

Equation 5 for the value of PVi in Equation 4 of 

this rule. 

Equation 5: 

PVF = PVU x [ 

100

(100 −% Filler)

] 

Where: 

PVF = The as-applied monomer VOC emission rate for the filled 

production resin or tooling resin, in 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 3 of this rule. 

% Filler = The weight percent of filler in the as-applied filled resin 

system. 

5.2.2.8 Work Practice Standards for Resins and Gel Coat 

 An operator shall ensure that all 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, except when material 

is being manually added or removed from a container, or when 

mixing or pumping equipment is being placed in or removed 

from a container. 

5.3 Organic Solvent Cleaning Requirements 

5.3.1 An operator shall not use organic solvents for cleaning operations that 

exceed the VOC content limits specified in Table 4, in accordance with 

the corresponding effective date. 
 

 
  

Table 4 VOC Content Limits for Organic Solvents Used in Cleaning Operations 

Type of Solvent 

Cleaning Operation 

VOC Content Limit Grams of VOC/liter of 

material (lb/gal) 

A. Product Cleaning During Manufacturing 

Process or Surface Preparation for Coating 

Application 

25 (0.21) 

B. Repair and Maintenance Cleaning 25 (0.21) 

C. Cleaning of Polyester Resin Application 

Equipment 25 (0.21) 

5.3.2 In lieu of complying with the VOC content limits in Table 4, an operator 

may control VOC emissions from cleaning operations with an APCOapproved VOC emission control system that meets the requirements of 

Section 5.1.1.5 for the solvent cleaning operations. 

5.4 Solvent Storage and Disposal 

An owner or operator shall store or dispose of all uncured polyester resin 

materials, fresh or spent solvents, waste solvent cleaning materials such as 

cloth, paper, etc., coatings, adhesives, catalysts, and thinners in self-closing, 

non-absorbent and non-leaking containers. The containers shall remain closed at 

all times except when depositing or removing the contents of the containers or 

when the container is empty. 

6.0 Administrative Requirements 

6.1 Recordkeeping 

An operator subject to this rule shall maintain the following records: 

6.1.1 Daily records of the type and quantity of all resins, gel coats, fillers, 

catalysts, and cleaning materials (including cleaning solvents) used in 

each operation. Records shall also indicate the amount used and VOC 

content, in weight percent, of all polyester resin and gel coat materials 

used for touch up, repair, and small jobs. 

6.1.2 Records of the VOC content, in weight percent, of all polyester resin and 

gel coat, filler materials, including the weight percent of non-monomer 

VOC content of the resin and gel coat, used or stored at the stationary 

source. 

6.1.3 Records of the VOC content of all cleaning materials used and stored at 

the stationary source as specified in Section 5.3. 
 

 
  

6.1.4 Records showing the weight loss per square meter during resin 

polymerization for each vapor-suppressed resin. 

6.1.5 VOC Emission Control System Records 

An operator using a VOC emission control system pursuant to Section 

5.1.1.5 to comply with this rule shall maintain daily records of key 

system operating parameters to demonstrate continuous operation and 

compliance of the VOC emission control system during periods of 

emission-producing activities. Key system operating parameters are 

those parameters necessary to ensure compliance, including, but not 

limited to, temperature, pressure drop, and air flow rate. 

6.1.6 An operator claiming exemption under Section 4.1 shall maintain records 

of polyester materials usage to support the claim of exemption. 

6.1.7 The operator shall retain the records specified in Sections 6.1.1 through 

6.1.6, as applicable, on site for a period of five years, make the records 

available on site during normal business hours to the APCO, ARB, or 

EPA, and submit the records to the APCO, ARB, or EPA upon request. 

6.2 Test Methods 

The analysis of cleaning materials, polyester resin materials and control 

efficiency shall be determined by the following methods: 

6.2.1 The emission rate per square meter of exposed surface during 

polymerization of Polyester Resins is to be determined using: 

SCAQMD Method 309 (Static Method for Determination of Volatile 

Emissions from Polyester and Vinyl Resins Operations), Attachment 

A, 1/8/91. 

6.2.2 Determination of Overall Capture and Control Efficiency of VOC 

Emission Control Systems 

6.2.2.1 The capture efficiency of a VOC emission control system’s 

collection device(s) shall be determined according to EPA’s 

“Guidelines for Determining Capture Efficiency,” January 9, 

1995 and 40 CFR 51, Appendix M, Test Methods 204-204F, as 

applicable, or any other method approved by EPA, ARB, and 

the APCO. 

6.2.2.2 The control efficiency of a VOC emission control system’s 

VOC control device(s) shall be determined using EPA Test 

Methods 2, 2A, or 2D for measuring flow rates and EPA Test 
 

 
  

Methods 25, 25A, or 25B for measuring total gaseous organic 

concentrations at the inlet and outlet of the control device(s). 

EPA Method 18 or ARB Method 422 shall be used to determine 

the emissions of exempt compounds. 

6.2.2.3 For VOC emission control systems that consist of a single VOC 

emission collection device connected to a single VOC emission 

control device, the overall capture and control efficiency shall 

be calculated by using the following equation: 

CECapture and Control = [ CECapture x CEControl ] / 100 

Where: 

CECapture and Control = Overall Capture and Control Efficiency, in 

percent 

CECapture = Capture Efficiency of the collection device, 

in percent, as determined in Section 6.2.2.1. 

CEControl = Control Efficiency of the control device, in 

percent, as determined in Section 6.2.2.2. 

6.2.3 The monomer content of uncatalyzed resin materials is to be determined 

using ASTM D2369-87 (Standard Test Method for Volatile Content of 

Coatings) or SCAQMD Test Method 312. 

6.2.4 The VOC content of cleaning materials shall be determined using EPA 

Method 24 (40 CFR Part 60, Appendix A). 

6.2.5 Determination of emissions of VOC from spray gun cleaning systems shall 

be made using SCAQMD "General Test Method for Determining Solvent 

Losses from Spray Gun Cleaning Systems," October 3, 1989. 

6.2.6 The transfer efficiency of alternative coating application methods shall be 

determined in accordance with the SCAQMD method “Spray Equipment 

Transfer Efficiency Test Procedure for Equipment User,” May 24, 1989. 

6.3 Multiple Test Methods 

When more than one test method or set of test methods is specified for any 

testing, a violation of any requirement of this rule established by any one of the 

specified test methods or set of test methods shall constitute a violation of this 

rule.