PROPOSED September 20, 2007 

RULE 4661 ORGANIC SOLVENTS (Adopted May 21, 1992; Amended December 17, 1992; 

Amended December 9, 1999; Amended December 20, 2001; Amended May 16, 

2002; Amended [rule adoption date]). 

1.0 Purpose 

 The purpose of this rule is to limit the emissions of volatile organic compounds (VOCs) 

from the use of organic solvents. This rule also specifies the reduction, monitoring, 

reporting, and disposal requirements. 

2.0 Applicability 

 The provisions of this rule shall apply to any source operation that uses organic solvents 

unless the source operation is exempted under Section 4.0. 

3.0 Definitions 

3.1 APCO: as defined in Rule 1020 (Definitions).

3.2 ARB: California Air Resources Board.

3.1 3.3 Baked: heated to a temperature greater than 194oF for the purpose of curing or 

drying a coating, ink or adhesive. a process whereby the coated object is heated 

above ambient temperature to a temperature at or above 194°F for the purpose of 

curing or drying.

3.2 3.4 Dissolver: an organic solvent that is added to an adhesive, coating, or ink in 

order to melt or to liquefy solid particles. 

3.5 EPA: United States Environmental Protection Agency.

3.3 3.6 Exempt Compounds: all organic compounds not classified as VOC, as listed in 

the definition of VOC in Rule 1020 (Definitions). 

3.4 3.7 Grams of VOC per liter of Material: the weight of VOC per volume of material 

and is calculated by the following equation: 

Grams of VOC per liter of material = Ws – Ww – Wec

Vm 

Where: 

Ws = Weight of volatile compounds, in grams 

Ww = Weight of water, in grams 

Wec = Weight of exempt compounds, in grams 

Vm = Volume of material, in liters. 

3.5 3.8 Heat-Cured or Heat-Polymerized: heated to a temperature less than or equal to 

194o

F for the purpose of curing a coating, ink or adhesive. 

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PROPOSED September 20, 2007 

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

3.6 3.10 Organic Solvent: the same as “Solvent.” 

3.7 3.11 Organic Solvent Cleaning: as defined in Rule 4663 (Organic Solvent Cleaning, 

Storage, and Disposal). 

3.8 3.12 Photochemically Reactive Solvent: any organic solvent with an aggregate of 

more than 20% of its total volume composed of chemical compounds classified 

below or which exceeds any of the following individual percentage composition 

limitations referring to the total volume of solvent: 

3.8.1 3.12.1 A combination of hydrocarbons, alcohols, aldehydes, esters, ethers 

or ketones having an olefinic or cycloolefinic type of unsaturation: five 

(5) percent; or 

3.8.2 3.12.2 A combination of aromatic compounds with eight (8) or more carbon 

atoms to the molecule except ethylbenzene: eight (8) percent; or 

3.8.3 3.12.3 A combination of ethylbenzene, ketones having branched 

hydrocarbon structures, or toluene: 20%. 

Whenever any organic solvent or any constituent of an organic solvent may be 

classified from its chemical structure into more than one (1) of the above groups 

of organic compounds, it shall be considered as a member of the most reactive 

chemical group, that is, that group having the least allowable percentage of the 

total volume of solvents. 

3.13 SCAQMD: South Coast Air Quality Management District.

3.9 3.14 Solvent: as defined in Rule 4663 (Organic Solvent Cleaning, Storage, and 

Disposal). 

3.10 3.15 Standard Conditions: as defined in Rule 1020 (Definitions). 

3.11 3.16 Thinner or Viscosity Reducer: an organic solvent which is added to an 

adhesive, coating, or ink to make it more fluid used to dilute coatings to reduce 

viscosity, color strength, and solids, or to modify drying conditions. 

3.12 3.17 Volatile Organic Compound (VOC): as defined in Rule 1020 (Definitions). 

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PROPOSED September 20, 2007 

4.0 Exemptions 

The provisions of this rule shall not apply to: 

4.1 The manufacture of organic solvents, or the transport of organic solvents or 

materials containing organic solvents. 

4.2 Any source operation that is subject to or specifically exempted by any of the 

following rules or an EPA approved version of the applicable listed rule: 

4.2.1 Rule 4601 (Architectural Coatings), 

4.2.2 Until December 31, 2008, Rule 4602 (Motor Vehicle and Mobile 

Equipment Coating Operations), 

4.2.3 Rule 4603 (Surface Coating of Metal Parts and Products), 

4.2.4 Rule 4604 (Can and Coil Coating Operations), 

4.2.5 Rule 4605 (Aerospace Assembly and Component Coating Operations), 

4.2.6 Rule 4606 (Wood Products Coating Operations), 

4.2.7 Rule 4607 (Graphic Arts), 

4.2.8 Rule 4610 (Glass Coating Operations), 

4.2.9 On and after January 1, 2009, Rule 4612 (Motor Vehicle and Mobile 

Equipment Coating Operations – Phase II)

4.2.9 4.2.10 Rule 4653 (Adhesives), 

4.2.10 4.2.11 Rule 4662 (Organic Solvent Degreasing Operations), 

4.2.11 4.2.12 Rule 4684 (Polyester Resin Operations), or 

4.2.12 4.2.13 Rule 4691 (Vegetable Oil Processing Operations). 

4.3 The spraying or other employment of insecticides, pesticides or herbicides. 

4.4 The employment, application, evaporation, or drying of saturated halogenated 

hydrocarbons or perchloroethylene. 

4.5 The use of any material, in any source operation described in Sections 5.1, 5.2, 

5.3, or 5.4 if all of the following conditions are met: 

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4.5.1 The volatile content of material consists only of water and organic 

solvents, and 

4.5.2 The organic solvents content comprises not more than 20 percent by 

volume of the total volatile content, and 

4.5.3 The volatile content is not photochemically reactive, and 

4.5.4 The organic solvent does not come into contact with flame. 

5.0 Requirements 

5.1 Sections 5.2 through 5.7 shall remain in effect until [6 months after rule adoption 

date].

5.1 5.2 Solvents Subjected to Heat: An operator shall not discharge into the atmosphere 

more than 15 pounds of VOC emissions in any one (1) day from any source 

operation in which any organic solvent or any material containing organic 

solvents comes into contact with a flame or is baked, heat-cured, or heatpolymerized in the presence of oxygen, unless the VOC emissions have been 

reduced through the operation of an APCO-approved VOC emissions control 

device system with an overall capture and control efficiency of at least 85 percent 

by weight. Those portions of any series of source operation designed for 

processing continuous web, strip, or wire that emit VOCs in the course of using 

operations described in this section shall be collectively subject to compliance 

with this section. 

5.2 5.3 Photochemically Reactive Solvents: An operator shall not discharge into the 

atmosphere more than 40 pounds of VOC emissions in any one (1) day from any 

source operation resulting from conditions other than those described in Section 

5.1 for employing or applying any photochemically reactive solvent, or any 

material containing such photochemically reactive solvent, unless the VOC 

emissions have been reduced through the operation of an APCO-approved VOC 

emissions control device system with an overall capture and control efficiency of 

at least 85 percent by weight. Emissions resulting from baking, heat-curing, or 

heat-polymerizing, as described in Section 5.1 5.2 of this rule, shall be excluded 

from determination of compliance with this section. Those portions of any series 

of source operation designed for processing a continuous web, strip, or wire that 

emit VOCs in the course of using operations described in this section shall be 

collectively subject to compliance with this section. 

5.3 5.4 Non-photochemically Reactive Solvents: An operator shall not discharge into 

the atmosphere more than 3,000 pounds of VOC emissions in any one (1) day 

from any source operation in which any non-photochemically reactive organic 

solvent or any material containing such a solvent, is employed or applied, unless 

VOC emissions have been reduced through the operation of an APCO-approved 

VOC emissions control device system with an overall capture and control 

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PROPOSED September 20, 2007 

efficiency of at least 85 percent by weight. Emissions resulting from baking, 

heat-curing, or heat-polymerizing, as described in Section 5.1 5.2 of this rule, 

shall be excluded from determination of compliance with this section. Those 

portions of any series of source operation designed for processing a continuous 

web, strip, or wire that emit VOCs in the course of using operations described in 

this section shall be collectively subject to compliance with this section. 

5.4 5.5 Cleanup: Emissions of VOCs into the atmosphere resulting from cleanup 

operations utilizing photochemically reactive organic solvents, from any source 

operation described in Sections 5.1, 5.2, or 5.3 5.2, 5.3, or 5.4 shall be included 

with other emissions of VOCs from that source operation for determining 

compliance with this rule. 

5.5 5.6 Post Removal Drying: Emissions of VOCs into the atmosphere as a result of 

spontaneously continuing drying of products for the first 12 hours after their 

removal from any source operation described in Sections 5.1, 5.2, or 5.3 5.2, 5.3, 

or 5.4 shall be included with other emissions of VOCs from that source operation 

for determining compliance with this rule. 

5.6 5.7 Monitoring: An operator incinerating, adsorbing, or otherwise processing 

organic solvents pursuant to this rule shall provide, properly install and maintain 

in calibration, in good working order and in operation, devices as specified in the 

Authority to Construct or the Permit to Operate, or as specified by the APCO, for 

indicating temperatures, pressures, rates of flow or other operating conditions 

necessary to determine the degree and effectiveness of air pollution control the 

VOC emission control system. 

5.8 On and after [6 months and one day after rule adoption date], from all VOCcontaining materials, equipment, and processes subject to this rule, an operator 

shall not emit to the atmosphere VOCs in excess of 833 pounds VOC per calendar 

month per facility.

5.9 In lieu of meeting the VOC emission limit in Section 5.8, an operator may install 

and operate a VOC emission control system that meets the following 

requirements.

5.9.1 The VOC emission control system shall be approved by the APCO.

5.9.2 The VOC emission control system shall have a capture efficiency of at 

least 90 percent by weight (90 wt%) and a control efficiency of at least 95 

wt%.

5.7 Storage and Disposal of Solvents: An operator shall store or dispose of fresh or 

spent photochemically reactive solvents, or any materials containing 

photochemically reactive solvents, solvent-laden wiping materials such as cloth, 

paper, etc., in closed, non-absorbent and non-leaking containers. The containers shall 

4661 - 5 Proposed Amendments to Rule 4661
PROPOSED September 20, 2007 

remain closed at all times except when depositing or removing the contents of the 

containers. Section 5.7 shall remain in effect until November 14, 2002.

5.8 5.10 Organic Solvent Cleaning, Storage, and Disposal Requirements: Effective on 

and after November 15, 2002, o Operators shall comply with the requirements of 

Rule 4663 (Organic Solvent Cleaning, Storage, and Disposal) when performing 

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

solvent materials, coatings, adhesives, catalysts, and thinners. See Sections 5.0 

and 6.0 of Rule 4663 for solvent VOC content limits, work practices, 

recordkeeping, and testing requirements. 

6.0 Administrative Requirements 

6.1 Recordkeeping 

An operator of any source operation subject to this rule shall maintain the records 

required by Sections 6.1.1 and 6.1.2 for a period of five (5) years. The records 

shall be made available to the APCO upon request.

6.1.1 Until [six months after rule adoption date], Tthe records shall identify the 

organic solvents used in all source operations and shall include the name of 

each organic solvent, solvent manufacturer’s name, chemical composition, 

VOC content, vapor pressure, amount used. 

6.1.1.1 An operator of a coating operation subject to this rule shall 

maintain daily records. 

6.1.1.2 For other operations subject to this rule, records may be kept on an 

extended basis, but not to exceed monthly, and shall not exceed a 

period during which the amount of VOC emissions exceeds the 

applicable daily VOC emission limits in the rule. 

6.1.1.3 Solvent purchase records and other such records needed to verify 

compliance of emissions limits of the rule shall also be kept. 

6.1.1.4 Effective on and after November 15, 2002, oOther such records, 

including the amount of VOC emissions resulting from organic 

solvent cleaning operations subject to Rule 4663 utilizing 

photochemically reactive organic solvents, needed to verify 

compliance of emissions limits of the rule shall also be kept. 

6.1.1.5 Records of the boiling point and amount of waste or spent 

solvent disposed shall also be kept. Section 6.1.1.5 shall remain 

in effect until November 14, 2002.

6.1.2 On and after [six months and one day after rule adoption date], operators 

shall 

4661 - 6 Proposed Amendments to Rule 4661
PROPOSED September 20, 2007 

6.1.2.1 Materials List: An operator shall maintain and have available on 

site, a current list of materials in use which provides all of the data 

necessary to evaluate compliance including the following 

information as applicable:

6.1.2.1.1 Specific manufacturer’s name of solvent-containing 

material, including solvents, catalysts, and thinners.

6.1.2.1.2 VOC content of each solvent-containing material, as 

used, in g/l or lb/gal.

6.1.2.2 Material Usage Records – An operator shall maintain usage 

records on a daily basis that include the following information:

6.1.2.2.1 Specific material.

6.1.2.2.2 Volume of material used (gallons).

6.1.2.2.3 Specific solvents, catalysts and thinners added to 

material.

6.1.2.2.4 Volume of each solvent, catalyst and thinner (gallons) 

added.

6.1.2.2.5 When the material is a mixture of different materials 

that are blended by the operator, the mix ratio of the 

batch shall be recorded and the VOC content of the 

batch shall be calculated and recorded in order to 

determine compliance with the VOC emission limits.

6.1.3 VOC Emission Control System Records

An operator using a VOC emission control system as a means of 

complying with this rule shall maintain daily records of key system 

operating parameters which will demonstrate continuous operation and 

compliance of the VOC emission control system during periods of 

emission-producing activities.

6.1.4 Records Retention

An operator shall retain records required in Sections 6.1.1 through 6.1.3, 

as applicable, on site for a minimum of five (5) 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 

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PROPOSED September 20, 2007 

6.2.1 Determination of VOC Content 

6.2.1.1 The VOC content of organic solvents shall be determined by 

using United States Environmental Protection Agency (EPA)

Test Method 24 or 24A or by using the manufacturer’s product 

formulation data and the formula in Section 3.4 3.7. 

6.2.1.2 Exempt halogenated VOCs shall be determined by using the 

California Air Resources Board (ARB) Test Method 432 or 

South Coast Air Quality Management District (SCAQMD) Test 

Method 303. 

6.2.2 Determination of Overall Capture and Control Efficiency of VOC 

Emission Control Devices 

6.2.2.1 The capture efficiency of each collection device shall be 

demonstrated according to the EPA’s document “Guidelines for 

Determining Capture Efficiency,” dated January 9, 1995. An 

equivalent alternate test method may be used provided it has 

been approved by the EPA, ARB and the APCO. 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 the VOC emission control system’s 

control device and the emissions of VOCs, measured and 

calculated as carbon, shall be determined by using EPA Methods 2, 

2A, or 2D for measuring flow rates and EPA Test Method 25, 25A, 

or 25B, as applicable for measuring total gaseous organic 

concentrations at the inlet and outlet of the control device. EPA 

Test Method 18 or ARB Method 422 shall be used to determine the 

emissions of exempt compounds. The control efficiency of the 

VOC emission control system’s control device shall be calculated 

by using the following equation: 

CECONTROL = [1 – ( VOCOUT / VOCIN )] x 100% 

Where: 

CECONTROL = Control Efficiency, in percent 

VOCIN = VOC content, in grams/liter, less exempt 

compounds and water, into the control device 

VOCOUT = VOC content, in grams/liter, less exempt 

compounds and water, out of the control device. 

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6.2.2.3 The overall capture and control efficiency shall be calculated by 

using the following equation 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 Determination of VOC Emissions 

6.2.3.1 The emissions of VOCs, measured and calculated as carbon, 

shall be determined by using EPA Test Method 25, 25A, or 25B, 

as applicable. EPA Test Method 18 or ARB Method 422 shall be 

used to determine the emissions of exempt compounds. 

6.2.3.1 6.2.3.2 Total VOC emissions per day shall be determined for each 

source operation by using the following equation: 

1001 454

1 1

 Total E / %)/( x ⎥

⎦

⎤ ⎢

⎣

⎡ ⎟

⎠

⎞ ⎜

⎝

⎛ ⎟ + − ⎠⎞ ⎜

⎝

⎛ = ∑∑= =

VLVL CE

n

m

mm

k

i

ii

Where: 

ETotal = Total VOC emissions, in pounds per day 

Li = Liters per day used of the “i”th organic solvent that 

is uncontrolled 

Vi = Grams of VOC per liter of material of the “i”th 

organic solvent that is uncontrolled 

Lm = Liters per day used of the “m”th organic solvent 

that is controlled 

Vm = Grams of VOC per liter of material of the “m”th 

organic solvent that is controlled 

CE = Overall capture and control efficiency of the control 

device, in percent, as determined in Section 6.2.2.3. 

6.2.4 Determination of Boiling Point and Vapor Pressure

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PROPOSED September 20, 2007 

6.2.4.1 The boiling point of organic solvents shall be determined by 

using either the manufacturer’s product formulation data or from 

publications such as Perry’s Chemical Engineer’s Handbook, 

CRC Handbook of Chemistry and Physics, Lange’s Handbook of 

Chemistry, or other District approved sources. Section 6.2.4.1 

shall remain in effect until November 14, 2002.

6.2.4.2 The vapor pressure of organic solvents shall be determined by 

using ASTM Method D2879 or from publications such as Perry’s 

Chemical Engineer’s Handbook, CRC Handbook of Chemistry 

and Physics, and Lange’s Handbook of Chemistry.

6.2.5 6.2.4 Multiple Methods of Determination 

VOC emissions and overall capture and control efficiency determined to 

exceed any limits established by this rule through the use of any of the 

above-referenced test methods and/or equations shall constitute a violation 

of the rule. 

7.0 Compliance Schedule

All rule provisions remain in effect on and after December 20, 2001, unless otherwise 

indicated.

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