GUIDELINES FOR ESTIMATING AND APPLYING RULE EFFECTIVENESS FOR 

OZONE/CO STATE IMPLEMENTATION PLAN 

BASE YEAR INVENTORIES 

Ozone and Carbon Monoxide Branch 

Air Quality Management Division 

Office of Air Quality Planning and Standards 

U.S. Environmental Protection Agency 

Research Triangle Park, North Carolina 27711 
 ii

 ADDENDUM

After preparation of this document, EPA decided to recommend 

additional flexibility in accounting for rule effectiveness (RE) 

in the development of base year emission inventories. This 

addendum provides guidance regarding that flexibility. 

METHODS FOR ACCOUNTING FOR RULE EFFECTIVENESS FOR VOLATILE ORGANIC 

COMPOUND (VOC) SOURCES 

A State or local agency that prepares VOC emission inventories may 

account for rule and control effectiveness by methods other than 

those specified in this document. Deviations from methods in 

document must meet the following criteria, as well as criteria 

specified in "Documentation and Concurrence," below: 

--In evaluating rule effectiveness under a method that deviates 

from the guideline, the State should consider: 

--The overall capture and control efficiency generally available 

from the kind of capture and control equipment being 

assessed; 

--Any stack test/performance evaluation that was performed on the 

capture and control equipment; 

--The rated capture and control efficiency (from manufacturer's 

specifications or literature); 

-- The kinds of activities that affect the determination of dayto-day performance of the capture and control equipment 

that are listed in the questionnaires that are contained 

in the guideline document (e.g., ease of determining 

compliance, type of control equipment, frequency and 

quality of inspections, level of training of inspectors). 

 

--The State or local agency should provide a way of determining 

which sources have applied control to avoid having planners 

"recontrol" already controlled sources. 

METHODS FOR ACCOUNTING FOR RULE EFFECTIVENESS FOR SOURCES OF 

OXIDES OF NITROGEN AND CARBON MONOXIDE 

 Rule effectiveness must be considered for sources of oxides of 

nitrogen and carbon monoxide where such sources are covered by 

rules or regulations in the State implementation plan (SIP). If a 

State or local agency does not use either the questionnaire method 

or the Stationary Source Compliance Division (SSCD) protocol, that 

agency should develop its own method for assessing RE and should 

not rely solely on the 80 percent default value. In evaluating 
 iii

rule effectiveness under such a method, the State should consider 

the kinds of activities that are listed in the questionnaires that 

are contained in the guideline document (e.g., ease of determining 

compliance, type of control equipment, frequency and quality of 

inspections, competence of inspectors). Methods for accounting 

for rule effectiveness different from the methods in the document 

must also meet the criteria specified in "Documentation and 

Concurrence," below. 

RARE CATASTROPHIC OR ACCIDENTAL RELEASES 

 Rare catastrophic or accidental releases may be inventoried in 

a manner deemed appropriate by the State or local agency; these 

releases do not necessarily need to be reflected in a rule 

effectiveness assessment, unless there is a pattern of reoccurrence. The methods developed must meet the criteria 

specified in "Documentation and Concurrence," below. 

DOCUMENTATION AND CONCURRENCE 

 The above paragraphs describe cases where methods that deviate 

from the methods in this document may be employed. In developing 

and using such a method, the following general criteria must be 

met: 

--The Regional Office, in consultation with the EPA Office of Air 

Quality Planning and Standards, must concur on the method. 

--Documentation must be available at the State or local agency for 

inspection by EPA; documentation does not have to be submitted 

with emission inventory. 
 iv

 TABLE OF CONTENTS 

Section Page

Addendum ....................................................... ii 

List of Tables ................................................. vi 

List of Figures ................................................ vi 

1INTRODUCTION ..................................................1 

1.1Background...................................................2 

 1.2 Meaning of Rule Effectiveness...........................3 

 1.3 Rule Effectiveness for Base Year Inventories............4 

11.4Factors Affecting Rule Effectiveness........................5 

 1.5 Calculating and Applying Rule Effectiveness.............5 

1.6References...................................................8 

2PROCEDURES FOR ESTIMATING CATEGORY-SPECIFIC RE.................9 

 2.1Determining Sources for Application of Rule Effectiveness9 

2.1.1 Excepted Sources................................9 

2.1.2 Direct Determination of Emissions..............11 

2.1.2.1 Criteria for Direct Determination 

 Emissions..................................12 

 2.1.2.2 Example of Direct Determination............12 

 2.1.2.3 Major Classes of Emissions 

 Estimation Techniques......................13 

 2.1.2.4 Documenting Direct Determination...........15 

2.2Overview of Applicable Approaches for 

 Determining RE.........................................16 

2.3Default Value Approach......................................16 

2.4Questionnaire Approach......................................18 

2.4.1 Level of Effort................................18 

2.4.2 Procedure......................................19 

2.4.2.1 Identifying Personnel to Perform 

 the Evaluation.............................19 

2.4.2.2 Preliminary Screening of Sources ..........19 

2.4.2.3 Choosing Sources to Evaluate...............20 

 2.4.2.4 Sources with Control Efficiencies 

 Greater Than 95 Percent....................21 

2.4.2.5 Answering the Questionnaires...............22 

2.4.2.6 Determination of Rule Effectiveness 

 Values.....................................22 

2.5SSCD Study Approach.........................................23 

2.5.1 Purpose of the Study...........................23 

 2.5.2 Summary of the SSCD Study 

 Approach Procedures............................24 

2.5.3 Calculating RE from an SSCD Study .............25 

2.6Using Results from SSCD Studies, 

 Questionnaires and the Default.........................27 
 TABLE OF CONTENTS (continued) 

Section Page

 v

3APPLICATION OF RULE EFFECTIVENESS IN 

 BASE YEAR INVENTORIES......................................30 

 33.1Introduction...........................................30 

3.2Calculating Rule-Affected Emissions.........................30 

33.2.1 Control Efficiency....................................31 

3.2.2 AIRS Coding............................................33 

3.3Documenting Rule Effectiveness for the 

 SIP Submittal..........................................34 

 3.4 References.............................................34 

4EXAMPLE CALCULATIONS..........................................36 

 4.1 Point Sources..........................................36 

4.1.1 Bulk Terminals (Loading Racks).........................36 

 4.1.2 Beverage Can Coating...........................37 

4.1.3 Paper Coating Facility.................................40 

 4.1.4 Metal Furniture Coating........................40 

4.1.5 Automobile Assembly Plant..............................41 

 4.1.6 Large Appliance Coating........................42 

4.1.7 Large Petroleum Dry Cleaner............................43 

 4.1.8 Graphic Arts...................................43 

 4.2 Area Sources...........................................45 

4.2.1 Stage I (Area Source Category).........................45 

 4.2.2 Architectural Coating 

 (Area Source Category).........................46 

APPENDIX A: RULE EFFECTIVENESS EVALUATION 

 FORM-POINT SOURCES................................A-1 

APPENDIX B: RULE EFFECTIVENESS QUESTIONNAIRE-AREA 

 SOURCE CATEGORIES.................................B-1 

APPENDIX C: DIRECT DETERMINATION EXAMPLE......................C-1 

APPENDIX D: DETERMINING SAMPLE SIZE...........................D-1 

APPENDIX E: DEFAULT CONTROL ASSUMPTIONS FOR 

 CTG CATEGORIES....................................E-1 
 vi

 LIST OF TABLES 

Number Page

1-1 Factors Influencing Rule Effectiveness......................6 

1-2Applying RE in Base Year SIP Inventories.....................7 

2-1Source Categories Covered by EPA Control 

 Techniques Guidelines (CTGs)...............................10 

2-2 Direct Determination Scenarios.............................12 

2-3 Emission Estimation Methods................................14 

2-4 Documenting Direct Determination for Surface Coating.......17 

2-5 Example of Weighted RE Value Using Questionnaire ..........24 

2-6 Combining SSCD Study and Questionnaire Approaches..........29 

3-1 Default Petroleum Storage Tank Control Efficiencies........32 

3-2 Coding RE in Electronic Inventory Submittals...............34 

D-1 Sensitivity Analysis of Sample Size: 

 Confidence Level = 90%....................................D-5 

D-2 Sensitivity Analysis of Sample Size: 

 Confidence Level = 95%....................................D-6 

D-3 Sensitivity Analysis of Sample Size: 

 Confidence Level = 99%....................................D-7 

E-1 Typical VOC Reduction per Facility for CTG Categories 

 Based on CTG Documents....................................E-3 

 LIST OF FIGURES 

Number Page

2-1 Comparison of the Questionnaire and SSCD Study.............28 
 LIST OF FIGURES (continued) 

Number Page

 1

SECTION 1 

INTRODUCTION 

 Emission inventories are assembled with the intent to provide 

the most accurate, representative emissions estimates available. 

 The 1990 Clean Air Act Amendments (CAAA) require base year 

annual and daily actual emission inventories to be gathered as 

part of the State implementation plan (SIP) for areas not in 

attainment for the current ozone and/or carbon monoxide (CO) 

national ambient air quality standards (NAAQS). These estimates 

are used to support inventory projections, ambient modeling 

applications, attainment strategy (regulatory) development and 

subsequent (periodic) inventories. 

 Prior to the post-1987 SIP requirements, SIP inventories and 

their applications assumed that regulatory programs for 

stationary sources were being and would continue to be 

implemented with full effectiveness, achieving all of the 

reported, required or intended emission reductions, and 

maintaining that level over time. However, experience during the 

decade of the 1980s has shown these regulatory programs to be 

less than 100 percent effective in achieving the necessary 

emissions reductions in most areas of the country. This means 

that SIP's before 1987 typically have understated actual 

emissions in both the baseline and projected inventories, 

resulting in lower emission reduction targets than were actually 

necessary to attain the NAAQS. 

 To avoid these miscalculations and more accurately estimate 

actual emissions, consideration shall be made for "rule 

effectiveness." This document provides guidelines for 

calculating and applying rule effectiveness in SIP base year 

inventories. The concepts and procedures discussed herein 

currently apply to ozone nonattainment area inventories, but will 

be applicable to SIP inventories for other pollutants as the need 

arises. This guidance focuses on developing estimates of rule 

effectiveness (RE) for the inventory that are used to obtain more 

realistic emission estimates for source categories. 

 This guidance describes the procedures developed by the 

Office of Air Quality Planning and Standards (OAQPS) to estimate 

the effectiveness of existing regulatory programs to achieve 

emissions control for stationary sources. One approach is the 

detailed study protocol developed by the Environmental Protection 

Agency (EPA) Stationary Source Compliance Division (SSCD) 

involving on-site inspection and testing on a single source 
 LIST OF FIGURES (continued) 

Number Page

 2

category by source category basis. The second approach, 

developed by the Air Quality Management Division (AQMD), involves 

answering generic questionnaires using available file information 

for specific sources and extrapolating the results to other 

sources in the same source categories. The third option is to 

use the 80 percent default for estimating RE. The results of 

these approaches are to be used to estimate RE for the base year 

emission inventories being prepared in response to the 1990 CAAA 

calls for ozone and CO SIP's. 

 The document is divided into four main sections. The 

remainder of Section 1 discusses the definitions and roles of 

various types of effectiveness measures that have historically 

been referred to as "rule" effectiveness and introduces the 

concepts covered in this guidance. Section 2 describes the 

procedures to be used in estimating category-specific RE values 

for States that choose not to use the 80 percent default. 

Section 3 contains instructions on how to apply RE to sources in 

the base year inventories, including a discussion of direct 

determination of emissions. Section 4 provides RE examples to 

aid in the calculation of emissions for base year inventories. 

Appendices A and B contain the point and area source RE 

questionnaires, respectively; Appendix C illustrates direct 

determination and Appendix D provides statistical guidelines for 

sample selection for the point source questionnaire. Appendix E 

presents typical VOC emissions reductions for Control Techniques 

Guideline categories. 

2.1BACKGROUND

 On November 24, 1987, EPA proposed the post-1987 ozone/CO 

policy.1

 A key component of this policy was the proposal that 

States account for the actual effectiveness of both present and 

future regulatory programs. This measure was termed "rule" 

effectiveness and represented the actual degree of source 

compliance. For stationary sources, EPA proposed that a baseline 

assumption of 80 percent RE should be applied to all regulated 

source categories in the inventory until a local categoryspecific evaluation could be completed to ascertain the actual 

category-specific effectiveness. (This 80 percent default value 

was initially based on a survey of several states that estimated 

the actual effectiveness of their emissions rules.) 

 EPA received numerous comments regarding the RE requirements 

proposed in that policy. None of the commenters challenged the 

concept of applying RE in the inventories or of improving the RE 

of particularly troublesome categories. Many commenters, 
 LIST OF FIGURES (continued) 

Number Page

 3

however, suggested that EPA provide an alternative to the acrossthe-board 80 percent presumption. The general theme contained in 

these comments suggested that EPA should allow State and local 

agencies flexibility in making RE estimates so that regulatory 

programs showing good compliance rates for certain source 

categories could receive higher credit than those showing lower 

compliance rates.2

 EPA provided guidance to the States in preparing the new SIPs 

pursuant to Title I of the CAAA through the Federal Register 

(General Preamble for Title I Implementation, April 16, 1992). 

EPA policy requires that base year stationary source inventories 

of volatile organic compounds (VOCs), nitrogen oxides (NOx) and 

carbon monoxide (CO) be adjusted for RE, using either the 80 

percent default value or the results from one of the procedures 

described herein. 

2.3MEANING OF RULE EFFECTIVENESS

 RE reflects the ability of a regulatory program to achieve 

all the emission reductions that could have been achieved by full 

compliance with the applicable regulations at all sources at all 

times. The precise degree to which all affected sources comply 

with a particular regulation over time is virtually impossible to 

ascertain without continuously monitoring emissions at all 

sources. RE can be estimated, however, by evaluating the success 

of a regulatory program at a few sources and extrapolating the 

results to others. 

 RE requires an understanding of a source's uncontrolled 

emissions and the control placed on that source, rather than the 

controlled emissions. As demonstrated in Section 4, the RE value 

is applied to adjust the control efficiency and is not applied to 

the emission estimate directly. For example, 80 percent RE means 

the control effectiveness is actually 80 percent of the estimated 

control efficiency; it does not mean that actual emissions are 20 

percent greater than estimated. 

 The appropriate method for determining and using RE depends 

upon the purpose for the determination: compliance, program or 

inventory. RE discussed outside the particular purpose may be 

generically referred to as control effectiveness. The following 

 

2

The issue of the creditability of RE improvements towards meeting reduction 

goals is not discussed in this document. Creditability will be included in a 

more general discussion of rule effectiveness in forthcoming guidance. 
 LIST OF FIGURES (continued) 

Number Page

 4

three common uses for a control effectiveness estimate have 

historically been called rule effectiveness: 

•Identifying and addressing weaknesses in control strategies 

and regulations related to compliance and enforcement 

activities (more accurately called Compliance 

Effectiveness) 

•Defining or refining the control strategy necessary to 

achieve the required emissions reductions designated in 

the CAAA (more accurately called Program or SIP Design 

Effectiveness) 

•Improving the accuracy or representativeness of emission 

estimates across a nonattainment area (hereafter called 

Rule Effectiveness) 

Each user needs to determine the effectiveness of rules and 

controls in reducing emissions to the desired level as it relates 

to the specific purpose. For example, SIP planners are concerned 

with the ability of the SIP strategy to meet specific ambient 

pollutant targets. Compliance personnel are interested in the 

relationship between actual and permissible emissions for a 

particular source or source category. Inventory personnel need 

to know the expected exceedance of emissions from the base 

estimate. This document concentrates on RE; Program and 

Compliance Effectiveness will be addressed in subsequent 

guidance. 

2.5RULE EFFECTIVENESS FOR BASE YEAR INVENTORIES

 The inventory RE is an adjustment to estimated emissions data 

to account for emissions underestimates due to compliance 

failures and the inability of most inventory techniques to 

include these failures in an emission estimate. The RE 

adjustment accounts for known underestimates due to noncompliance 

with existing rules, control equipment downtime or operating 

problems and process upsets. The result is a best estimate of 

actual base year emissions, leading to more reliable estimates of 

expected emission reductions and control measure effectiveness in 

future years. EPA requires that base year SIP inventories apply 

and report RE.3

 Base year inventory RE considers that emission changes 

brought on by growth, production changes, etc. are artifacts that 

should be excluded when determining RE. RE simply adjusts the 

estimated emissions for the effects of noncompliance. By 
 LIST OF FIGURES (continued) 

Number Page

 5

definition, all source categories for which a regulation exists 

should have an RE value between zero and 100 percent (i.e., source categories for which no regulation exists would have no RE 

factor associated with them). To say that a particular 

regulation was 100 percent effective would mean that the 

regulatory agency could ensure complete and continual compliance 

at all sources covered by the regulation, with no incidence of 

control equipment failure or process upset at any source and no 

sources evading control requirements. To say that a regulation 

was zero percent effective would mean that no sources in the 

category had made any effort to comply with the applicable 

regulation. RE cannot be less than zero or greater than 100 by 

definition. 

 The connection between SIP rules and actual emissions 

reductions is that State or local agencies must assume that there 

will be less than 100 percent compliance of rules in the absence 

of other information. Otherwise, rules will not actually achieve 

the intended reductions mandated in Section 182(b)(1) of the 

CAAA: 15 percent over 6 years and 3 percent per year thereafter 

until attainment is reached. 

2.7FACTORS AFFECTING RULE EFFECTIVENESS

 There is no succinct mathematical formula that adequately 

accounts for the many different variables influencing RE, 

although it can be thought of as a complex function of the 

following types of factors: the nature of the regulation, the 

nature of techniques used to comply with the regulation, the 

performance of each source in complying with the regulation, and 

the performance of the implementing agency in enforcing the 

regulation. Table 1-1 lists specific examples of each type of 

factor. The list is not exhaustive, however, it demonstrates the 

large number and wide variety of factors that affect RE. 
 LIST OF FIGURES (continued) 

Number Page

 6

TABLE 1-1. FACTORS INFLUENCING RULE EFFECTIVENESS 

Nature of the Regulation 

•possible ambiguity or deficiencies in wording 

•level of detail of recordkeeping required 

•level of complexity of compliance determination 

•inadequate test methods 

Nature of Techniques Used to Comply With Regulation 

•level of confidence in long-term capabilities of control technique 

(i.e., whether the emissions control is prone to failure or 

degradation even with adequate attention) 

•complexity of control technique (i.e., likelihood that operator error 

or variability in operator technique could affect compliance) 

•potential for fugitive emissions not ducted to control device (i.e., 

adequacy of emissions capture system) 

Performance of Source in Complying With Regulation 

•trained individual responsible for complying with environmental 

regulations 

•schedule for maintenance and inspection of control equipment 

•adequacy of recordkeeping practices (i.e., can compliance be determined 

from available records?) 

•ensurance of compliance over time, considering the previous record of 

process upsets or control equipment malfunction 

•timeliness of response to notices of violation 

Performance of Implementing Agency in Enforcing Regulation 

•attention and resources directed at this source or source category 

•communications effort, with respect to compliance requirements 

•completeness of data maintained on file 
 LIST OF FIGURES (continued) 

Number Page

 7

2.9CALCULATING AND APPLYING RULE EFFECTIVENESS

 The remainder of this document explains the calculation of RE 

values and the adjustment of base year emissions for RE. Every 

base year SIP inventory must apply RE according to the guidelines 

set forth herein. The process of examining and applying RE 

entails the basic steps listed in Table 1-2. These steps are 

explained in detail in the following chapters. 
 LIST OF FIGURES (continued) 

Number Page

 8

 

TABLE 1-2. APPLYING RE IN BASE YEAR SIP INVENTORIES 

Step Considerations 

Determine 

relevant 

emissions 

categories 

Source categories which are subject to 

emission controls (i.e., there is a rule 

in place) during the year of inventory

should be considered. 

Identify exempt 

sources 

Emissions from sources with 

uncontrolled, directly determined or 

permanently eliminated emissions are 

exempt from adjustment for RE. 

Calculate a RE 

value (%) for 

each relevant 

category 

Agencies calculate RE values derived 

from an SSCD study, the questionnaires 

included in this guidance or the default 

value. Questionnaires require a survey 

of sources in the categories identified 

in the first step. 

Calculate 

control 

efficiency for 

each affected 

source 

A reasonable estimate of the emissions 

control efficiency for each source is 

essential to the RE calculation. This 

efficiency may be measured or estimated 

based on the control device or estimated 

based on the rule in place. 

Calculate base 

year emissions 

(adjusted for 

RE) 

Emissions are adjusted for RE as 

described in this document using 

uncontrolled emissions, control 

efficiency and the RE value; these 

emissions are the SIP base year 

emissions. 

Document RE 

calculations 

When submitting the SIP inventory, 

agencies should document the procedures 

and calculations made to show that RE 

has been appropriately addressed, 

including criteria used to exempt 

sources. 
 LIST OF FIGURES (continued) 

Number Page

 9
 LIST OF FIGURES (continued) 

Number Page

 10
 LIST OF FIGURES (continued) 

Number Page

 11

2.11REFERENCES

1.State Implementation Plans; Approval of Post-1987 Ozone and 

Carbon Monoxide Plan Revisions for Areas Not Attaining the 

National Ambient Air Quality Standards; Notice, Federal 

Register, Vol. 52, No. 226, November 24, 1987. pp. 45044-

45122. 

2.U.S. Environmental Protection Agency, Procedures for Estimating 

and Applying Rule Effectiveness in Post-1987 Base Year 

Emission Inventories for Ozone and Carbon Monoxide State 

Implementation Plans, Office of Air Quality Planning and 

Standards, Research Triangle Park, NC, June 1989. 

3.U.S. Environmental Protection Agency, Emission Inventory 

Requirements for Ozone State Implementation Plans, EPA-450/4-91-010, Office of Air Quality Planning and 

Standards, Research Triangle Park, NC, March 1991. 
 LIST OF FIGURES (continued) 

Number Page

 9

SECTION 1 

PROCEDURES FOR ESTIMATING CATEGORY-SPECIFIC RE 

2.1DETERMINING SOURCES FOR APPLICATION OF RULE EFFECTIVENESS

 Every source subject to an emission control regulation during 

the inventory period should be considered for application of RE. 

 For many nonattainment areas, the list of Control Techniques 

Guidelines (CTG) categories (Table 2-1) provides a starting point 

to identify regulated sources. It is important to include all 

regulated sources, regardless of whether the regulation had 

received official EPA approval prior to the inventory period. In 

some cases sources are exempted from emissions regulations if an 

emission cap (e.g., 25 tons VOC per year) is not exceeded as 

defined by the emission control rule. These sources are not 

necessarily subject to RE, although a State or local agency may 

choose to include these sources if compliance with the emissions 

cap is a known problem. Once the affected emissions categories 

and sources have been identified, each source is reviewed to 

determine the appropriate RE application. 
 LIST OF FIGURES (continued) 

Number Page

 10

TABLE 2-1. SOURCE CATEGORIES COVERED BY EPA CONTROL 

TECHNIQUES GUIDELINES (CTGs) 

Source Category CTG Group 

Categories Predominated by Point Sources 

Gasoline Loading Terminals 

Gasoline Bulk Plants 

Fixed Roof Petroleum Tanks 

Miscellaneous Refinery Sources 

I

I

I

I

Surface Coating of: 

 Cans 

 Metal Coils 

 Fabrics 

 Paper Products 

 Automobiles and Light Duty Trucks 

 Metal Furniture 

 Magnet Wire 

 Large Appliances 

 Miscellaneous Metal Parts 

 Flat Wood Paneling 

 Graphic Arts 

I

I

I

I

I

I

I

I

I

II

II

II

Leaks from Petroleum Refineries 

External Floating Roof Petroleum Tanks 

Gasoline Truck Leaks and Vapor Collection 

Synthetic Pharmaceutical Manufacturing 

Rubber Tire Manufacturing 

II

II

II

II

II

Equipment Leaks from Natural Gas/Gasoline Processing Plants 

Manufacture of HDPE, PP, and PS Resins 

Fugitive Emissions from SOC, Polymer, and Resin 

Manufacturing Equipment 

Large Petroleum Dry Cleaners 

SOCMI Air Oxidation Processes 

III

III

III

III

III

Categories Predominated by Area Sources 

Service Stations - Stage I 

Cutback Asphalt 

Solvent Metal Cleaning 

Commercial Dry Cleaning 

I

I

I

II
 LIST OF FIGURES (continued) 

Number Page

 11

2.2.1 Excepted Sources

 The following sources are exempt from the RE adjustment: 

•sources where no controls are required (i.e., the source is 

unregulated) 

•sources for which control is achieved by means of an 

irreversible process change that eliminates the use of 

VOC or the potential for CO emissions 

•sources for which emissions are calculated by means of a 

direct determination 

 For sources that are affected by a rule but are completely 

uncontrolled, a RE of zero percent should be recorded in the 

inventory. Sources using an irreversible process change to 

control emissions should be assumed to be achieving 100 percent 

RE. When emissions can be calculated by means of a direct 

determination, RE falls out of the calculation and, thus, is not 

applicable (i.e., the emissions estimate is not contingent on the 

effectiveness of controls). For all other types of sources, RE 

should be applied in a manner consistent with Section 3. 

 Uncontrolled Sources are exempt from application of RE. RE 

does not need to be determined for sources that are completely 

uncontrolled, including cases where the source is making no 

attempts at compliance (illustrated by the first screening 

question on the point source questionnaire (Appendix A)). In 

this situation, a regulation is considered to be totally 

ineffective. The RE for such a source would be zero and should 

be recorded as such in the base year inventory. 

 Irreversible Process Changes. An irreversible process change 

(in the context of this guidance) involves a process modification 

or equipment substitution that completely eliminates solvent use 

from the production process. Irreversible process changes thus 

preclude application of RE. Irreversible changes require that 

the process cannot be quickly or easily reversed. Examples of 

this would be substituting a hot-melt lamination process for 

solvent-based adhesives and installing powder coating equipment 

to replace solvent-based coatings and equipment. In general, the 

use of "exempt" solvents or compliance coatings3

 would not 

3

Compliance coatings include waterborne, low-solvent (high solids) and powder 

coatings. 
 LIST OF FIGURES (continued) 

Number Page

 12

constitute an irreversible process change. Although 

incorporating these materials into the production process may 

involve the installation of new equipment or the total redesign 

of a production line, a total elimination of the potential VOC 

use is required to be considered irreversible. (EPA recognizes 

that industries may switch back to old equipment and solventbased coatings; State and local agencies should exercise judgment 

in defining irreversibility.) Sources controlling emissions by 

an irreversible process change should be assigned a RE of 100 

percent in the inventory because the nature of the control 

technique ensures continual compliance over time. 

 Direct Determination is one in which emissions are calculated 

directly (e.g., explicit records for each type of coating and/or 

solvent used) rather than from estimates of uncontrolled 

emissions and level of control. Any calculation that involves 

estimates of production rates, capture efficiency, transfer 

efficiency or solvent consumption rates typically does not

qualify as a direct determination. Due to the importance of 

direct determination, it is discussed in more detail below. 

2.2.3 Direct Determination of Emissions

 As previously stated, direct determination means that no RE 

adjustment is necessary when computing base year emissions. That 

is, the emission estimate is not affected by a source's 

compliance or noncompliance with rules. Where an emissions 

measurement is made with a high degree of certainty, RE 

adjustment should not apply to that source. When reporting the RE 

value for these sources, use 100 percent rather than zero or "not 

applicable."4

 The benefit of directly determining emissions is 

that an accurate calculation of emissions is made without the 

inherent uncertainties of compliance and control efficiency. 

2.2.4.1 Criteria for Direct Determination of Emissions

 For an emissions estimate to qualify as a direct 

determination, it must meet certain criteria. First, emissions 

have to be calculated from explicit source records. Second, no

emissions factors or assumptions (e.g., for solvent content) can 

be used in the calculation. Generally, if a control device is in 

place, the estimate does NOT qualify as a direct determination. 

 

4

When reporting RE for sources where a rule applies and emissions were 

directly determined, report 100 percent. This reporting convention will 

clearly identify to any inventory reviewers that RE was considered for the 

source.
 LIST OF FIGURES (continued) 

Number Page

 13

The most common example of a direct determination of VOC 

emissions is "mass balance" accounting. The data for the direct 

determination must be accurate and well-documented. Each region, 

state or local agency may decide what constitutes an appropriate 

level of documentation for these data, consistent with EPA 

guidelines stated in Section 2.1.2.4. Supporting documentation 

for emissions estimates must be maintained by the State. 

2.2.4.3 Example of Direct Determination

 Table 2-2 shows two methods, both mass balance, that would 

qualify as direct determination under the current guidelines. 

Both situations imply that detailed records are available to the 

source and/or the air pollution control agency. 

 To illustrate direct determination, consider a manufacturing 

facility with a product coating operation achieving compliance by 

using low-solvent or waterborne coatings in lieu of control 

equipment. Emissions are directly determined and calculated by 

the following method: 

 Step 1determine coating and solvent usage over 

time (e.g., a typical month during the 

ozone season) from detailed plant 

records; 

TABLE 2-2. DIRECT DETERMINATION SCENARIOS

Process Method 

Description 

Comment 

Bulk 

Storage/ 

Solvent 

Use 

Solvent 

Metering (mass 

balance) 

1)Requires documentation by the 

source 

2)Generally applies to inks, 

coatings and solvents 

Solvent 

Use 

Accounting 

(mass balance) 

1)Requires documentation by the 

source (adequate paper trail 

such as purchasing records) 

2)Assumes 100 percent evaporation 

3)Solvent content may be 

determined by test or using 

manufacturers' records 
 LIST OF FIGURES (continued) 

Number Page

 14

 Step 2use manufacturer's specifications to obtain 

solvent content of all coatings used; 

 Step 3for each coating used, calculate amount of 

solvent used over time by multiplying 

usage (gal/month) by actual solvent 

content (lbs VOC/gal coating), as 

supplied by the manufacturer; 

 Step 4calculate the total amount of solvent used 

over time by adding the amount in each 

coating and the amount of raw solvent 

used for cleanup and dilution (lbs 

VOC/month); 

 Step 5assume that all solvent used was emitted to 

the atmosphere at some point within the 

plant unless manifests indicate that some 

amount was shipped offsite as waste or 

the source can document that some portion 

was incorporated into the product; and 

 Step 6calculate emissions in lbs VOC/day by 

dividing total solvent emitted (lbs 

VOC/month) by number of working days in 

that month (days/month). 

Appendix C illustrates this example in more detail. 

 Another example of direct determination is that estimated by 

some type of continuous emission monitoring (CEM) equipment. If 

used, such equipment must be capable of determining mass balance 

emissions over extended periods of time, and provisions must be 

made for malfunction in the CEM equipment itself. 

2.2.4.5 Major Classes of Emissions Estimation Techniques

 Table 2-3 lists the major classes of emissions estimation 

techniques and their potential for classification as a direct 

determination. Some classes are discussed in detail, although 

the salient points are contained in the table. 
 LIST OF FIGURES (continued) 

Number Page

 15

TABLE 2-3. EMISSION ESTIMATION METHODS

Method AIRS1

Code 

Applicability to Direct Determination

Stack Test/ 

Emissions Test 

1 Stack or emissions tests represent a 

"snapshot" of emissions at a single point in 

time and are not considered direct 

determinations. However, results of one or 

more emissions tests, used in conjunction 

with frequent tests of control device 

performance and a complete analysis of 

capture as well as control efficiency, may 

be considered as a direct determination in 

certain cases. 

CEM 1 Continuous emissions monitoring (CEM) for 

VOC and/or CO is theoretically possible. 

CEM would preclude any RE adjustment 

provided the CEM equipment is operating 

properly throughout the estimation period. 

Mass Balance 2 Mass balance is the technique usually 

considered for direct determination, 

provided adequate documentation of 

throughput and (VOC) content are available. 

 This technique generally is used for 

evaporative sources. Use of estimated

control/capture/transfer efficiencies in a 

calculation of emissions disqualifies the 

estimate as directly determined. The effect 

of regulatory or physical controls can only 

be estimated from the known inputs and 

outputs from the process. 

AP-42 Emission 

Factors 

3 or 

8 

AP-42 emission factors are not direct 

determinations. 

Other (State) 

Emission Factors 

5 or 

9 

Emission factors in general cannot be 

considered direct determinations. 

Engineering 

Analysis/ Other 

Methods 

4 Determination based on engineering 

principles or judgment cannot be direct 

determination. 

1

Aerometric Information Retrieval System
 LIST OF FIGURES (continued) 

Number Page

 16

 Stack tests/emissions tests are generally excluded as direct 

determinations because they are emissions "snapshots" rather than 

an accurate assessment of emissions over time. As such, stack 

tests are source-specific emission factors. However, such tests 

may be considered as direct determinations in conjunction with 

all of the following other data: 

•Records of control equipment function (efficiency and 

upsets) throughout the period. These include daily 

records of upsets and periodic (i.e., at least monthly) 

determinations of actual efficiency and maintenance. 

•A detailed and applicable study of capture efficiency. 

Emissions for processes that emit VOC are frequently 

estimated at the building vent or control device outlet. 

 These estimates do not account for the control device 

capture efficiency and emissions which "leak" from the 

building. These losses can be very significant prior to 

reaching the control device and must be factored into the 

emissions estimate. 

•Documentation that the emissions test remains applicable to 

the process and operations at the source. 

 Mass balance is the common term for estimating emissions 

based on subtracting the known outputs of the process from the 

inputs to the process. This is a well-respected method for 

determining emissions of SOx from combustion processes based on 

sulfur inputs to the process and chemical stoichiometry. To 

determine emissions for VOC, any organics incorporated in the 

product plus the amount of process fugitives captured (e.g., the 

amount of recycled solvent) is subtracted from the total VOC 

(typically solvent) input. No control or capture efficiency is 

necessary for this calculation. The efficiency of the regulatory 

or physical control is solely determined on the basis of measured 

process inputs and outputs. As discussed previously, this 

measurement process is restricted to documented metering or 

accounting of inputs and outputs. 

 Emission factors are not appropriate as direct determinations 

of emissions because they are not specific to the particular 

source. Even with the information discussed for emissions tests 

on capture efficiencies and control device operation, emission 

factors will not produce an estimate sufficiently reliable to the 

specific source to qualify as a direct determination. 
 LIST OF FIGURES (continued) 

Number Page

 17

2.2.4.7 Documenting Direct Determination

 The local or State air pollution control agency is ultimately 

responsible for determining the adequacy of documentation and 

application of directly determined emission estimates. Local and 

State agencies should maintain records necessary to document 

direct determinations and should be prepared to produce this 

documentation upon EPA's request. EPA is not requiring that 

these records be submitted with the SIP inventory; complete 

submittal of this information would unnecessarily increase the 

effort of the submittal process. 

 The following information illustrates the level of 

documentation required to support direct determination of surface 

coating emissions: 

 •Solvent (VOC) content of each coating type 

 •Accurate measure of the amount of each coating 

 •Amount of thinning and cleanup solvent 

 •Amount of waste solvent disposal offsite 

 •Adequate oversight of these records by State or local agency 

Table 2-4 suggests criteria for meeting and documenting these 

requirements. 
 LIST OF FIGURES (continued) 

Number Page

 18

 TABLE 2-4. DOCUMENTING DIRECT DETERMINATION FOR 

 SURFACE COATING

SOLVENT (VOC) CONTENT

Document Solvent or VOC Content of Every Coating 

•Periodic Testing of Actual Coatings 

•Manufacturer's Specifications for Coatings that Include Solvents 

•Material Safety Data Sheets (MSDS) with Information on Total VOC 

Content 

•Reflect Coatings in Use during the Inventory Period 

Total VOC Emitted = VOC Content x Total Coating Consumed 

COATING OR SOLVENT CONSUMPTION

Record Total Coating (or Solvent) Use Regularly 

•Daily or Batch by Batch Basis 

•Process by Process 

•Coating by Coating 

Use Purchasing Records if Necessary 

Make Records Available during Inspections 

Source May Submit Monthly or Quarterly Summaries 

THINNING AND CLEANUP SOLVENT

Include Thinner and Cleanup Solvent Consumption 

•Daily or Batch by Batch Records 

•Monthly or Quarterly Summaries 

SOLVENT DISPOSAL/RECYCLE

Give Credit for Offsite Disposal/Treatment 

•Submit Waste Transfer Records with Information on Amounts Shipped 

ADEQUATE OVERSIGHT

Inspect Regularly 

Check Facility's Summary Data against Daily Records during Inspection 

Check Records (e.g., Daily Summaries) against Records Kept "on the 

Floor." 

Investigate and Resolve any Discrepancies 
 LIST OF FIGURES (continued) 

Number Page

 19

2.3OVERVIEW OF APPLICABLE APPROACHES FOR DETERMINING RE

 In determining an RE value for adjusting the base-year VOC 

emissions inventory, State and local agencies may elect to 

(1) use an across-the-board RE presumption of 80 percent for all 

sources; (2) use the questionnaire approach to determine a 

category-specific RE value for both point sources and area 

sources; or (3) use or design a study specific to a category in 

accordance with the procedure developed by SSCD. The following 

sections discuss each of these methods for determining RE. 

2.5DEFAULT VALUE APPROACH

 In general, the 80 percent default RE value is used in the 

absence of a local category-specific evaluation (i.e., the 

questionnaire approach or the SSCD study approach). In essence, 

the 80 percent default value assumes that the ability to use 

control devices and existing rules to achieve a 100 percent 

compliance rate is only 80 percent effective. Therefore, the 

base year emissions inventory must be adjusted by this factor to 

ensure that the amount of emissions reductions necessary to 

achieve the CAAA-required reductions in VOC emissions can be met. 

 The RE value should be applied as discussed in Section 2.4, 

Questionnaire Approach. 

 A number of surveys were conducted to determine a 

representative default RE value, one of which was conducted by 

OAQPS of States in the Regional Oxidant Model Northeast Transport 

(ROMNET) region. This survey indicated that regulations and 

controls were approximately 80 percent effective, on average, in 

achieving the target emissions reductions. 

 Subsequent examination of the 1989 SSCD studies have allowed 

OAQPS to reexamine the 80 percent default value. The results of 

the 1989 SSCD RE studies conducted by States in 7 of the 10 EPA 

Regions also show an average RE value of approximately 80 percent 

when averaging the results obtained from three alternate methods 

(including the method contained in this guidance document) used 

to calculate RE for the SSCD study. Some of the RE studies 

indicated values in excess of 100 percent. These values are 

inappropriate in reviewing inventory RE. Values greater than 100 

percent imply that emissions for a category are less than 

estimated. The causes of "over-compliance" (i.e., decreased 

production) in these studies are already accounted for in the 

inventory emissions estimates. Values greater than 100 percent 
 LIST OF FIGURES (continued) 

Number Page

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were set equal to 100 percent. The results varied from about 70 

to 90 percent, depending on the selected calculation method. 

 It is difficult to estimate a particular category's RE for a 

particular area based on a small subset of studies such as the 

1989 SSCD RE studies. Where other data are unavailable to 

estimate category-specific RE, the 80 percent default value is 

the most appropriate based on the information currently 

available. 

2.7QUESTIONNAIRE APPROACH

 The intent of the questionnaire approach is to determine a 

category-specific RE value to adjust the baseline VOC emissions 

inventory for less than 100 percent regulatory compliance in a 

nonattainment area. This approach involves the use of 

questionnaires designed for both point and area sources and is 

based on information on file with the source and personnel 

familiar with the sources included in the study (Appendices A and 

B). (Sources to be included in the process must pass a 

preliminary screening test. An RE number is determined for each 

category in each nonattainment area.) 

2.7.1 Level of Effort

 The categories representing at least 80 percent of the 

emissions inventory must be surveyed with the questionnaire. The 

questionnaires contain a series of generic questions covering 

various factors which affect the RE determination. These factors 

include the nature of the regulation, the nature of techniques 

used to comply with each regulation, the performance of the 

source in complying with the regulations, and the performance of 

the implementing agency in enforcing the regulations. The 

questionnaire is designed to be answered using only available 

source file information, thus alleviating the need for source 

inspections. Prior to each source evaluation, the complete 

source file information is reviewed including reports of previous 

visits and inspections. Information pertaining to potential 

deviations or deficiencies in State regulations must also be 

reviewed prior to taking this approach. In many cases, 

knowledgeable inventory staff may be able to complete the 

questionnaires for a single source category in one-half day or 

less. 
 LIST OF FIGURES (continued) 

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2.7.3 Procedure

 The procedure involves the use of two generic questionnaires 

that are based on the factors listed above and in Table 1-1. One 

questionnaire is used for individual point sources (see Appendix 

A) and another for area source categories (see Appendix B). 

Table 2-1 listed source categories for which CTGs have been 

issued and provides a good starting point for State and local 

agencies to determine which questionnaire to apply. 

 Many States contain more than one nonattainment area, raising 

the issue of whether RE should be estimated on a local or 

statewide basis. In general, this procedure should be used to 

determine unique RE estimates for each nonattainment area, except 

in cases where statewide regulations are implemented by a single 

agency throughout the State. In this case, all nonattainment 

areas in the State may employ a single value. The appropriate 

EPA Regional Office should be contacted for guidance if there is 

any question of whether local or statewide estimates are 

appropriate in a particular State. 

2.7.4.1 Identifying Personnel to Perform the Evaluation

 In most cases, representatives from the State or local 

agency's SIP planning or inventory group and compliance group 

should oversee the RE evaluations described in this document, but 

this selection may vary based on the individual agency and 

personnel experience. (The person conducting each evaluation 

will be hereafter referred to as the "evaluator.") One of the 

goals of incorporating RE in the base year inventory is to have 

planning personnel become more aware of the extent to which 

sources are complying with SIP regulations and the actual 

emission reductions that have resulted. The evaluator should 

enlist the aid of the local inspector(s) most familiar with each 

source. The role of the EPA Regional Office generally will be to 

review the results of the individual evaluations and/or the final 

RE estimates. In specific cases where this arrangement is not 

satisfactory, States or local agencies may negotiate with the 

Regional Offices to modify the respective roles. 
 LIST OF FIGURES (continued) 

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2.7.4.3 Preliminary Screening of Sources

 Each point source chosen should be subjected to the 

preliminary screening test at the beginning of the point source 

questionnaire. This screening will determine the appropriateness 

of evaluating RE by means of the questionnaire procedure for the 

chosen sources. The questionnaire should NOT be used to 

determine RE for the chosen source if any of the following is 

true: 

•the source is not regulated5

•the source achieves emissions reduction by means of an 

irreversible process change that completely eliminates 

VOC from the process 

•emissions from the source are calculated by means of a 

direct determination 

 Sources for which any of the above is true should be excluded 

from the questionnaire evaluation and are exempt from the 

adjustment of emissions for RE. These exclusions were discussed 

in detail in Section 2.1.1. 

2.7.4.5 Choosing Sources to Evaluate

 State and local agencies choosing to develop categoryspecific RE estimates may (1) use the questionnaire procedure for 

ALL regulated stationary source categories in their inventories 

or (2) use the questionnaire for 80 percent of their emissions 

inventory and a combination of the default value or SSCD study 

for the remainder of the emissions. If a State or local agency 

wishes to use the questionnaire approach for a subset of emission 

categories, the following conditions must be met. At least 

80 percent of the total pollutant-specific emissions (e.g., VOC) 

must be covered by questionnaires and all categories representing 

5 percent or greater of the pollutant-specific emissions must use 

the questionnaire. Both conditions (80 percent coverage of total 

point source pollutant emissions and every category representing 

5 percent or more of the total point source pollutant emissions) 

must be met for the questionnaire approach. 

 

5

Unregulated sources which are controlled should have equipment downtime, 

actual operating efficiency and process upsets factored into the emissions 

estimate, although these sources are not technically subject to RE. 
 LIST OF FIGURES (continued) 

Number Page

 23

 The most accurate way to estimate RE for point source 

categories would be to evaluate all sources in each category for 

which a regulation exists and average the results. Since this 

would place an unreasonable burden on resources and time for the 

agency performing the evaluation, agencies should evaluate RE 

sources in each category for which a regulation exists according 

to the following guidance. If there are ten or fewer sources in 

a category, all sources should be included. If there are more 

than ten, choose ten at random, complete the questionnaires and 

determine if the sample size is adequate or needs to be expanded. 

 The point sources should be chosen randomly to avoid biasing the 

results. To assure statistical accuracy, use the procedure 

outlined in Appendix D for determining the sample size. (Area 

sources as defined by the emission inventory will be evaluated by 

category.) 

 One possible method for choosing random point sources is for 

the evaluator to obtain a list of all sources in the local 

inventory, grouped by source category. These sources should 

include the numerical identification codes and any other details 

necessary to obtain the appropriate file information. The 

evaluator might then enlist the aid of another employee who is 

unfamiliar with both the sources and the numerical coding system 

of sources in the air program. This employee would be presented 

with a list of only the numerical identification codes, not the 

company names, of all sources in the inventory grouped by source 

category, and asked to randomly choose a statistically valid 

sample from the necessary sources in each point source category 

for which a regulation exists. Alternately, there are many 

popular software packages (e.g., Lotus®) which are able to 

generate random numbers with a list of sources. 

2.7.4.7 Sources with Control Efficiencies Greater Than 95 Percent

 Source emissions may be artificially inflated when the 80 

percent default value for RE is applied to sources with stated 

control efficiencies greater than 95 percent. This is of 

particular concern when dispersion modeling is used. To ensure 

that emissions estimates are as accurate as possible, EPA has 

developed three different options to accommodate this situation. 

 Before selecting one of the following options, States should 

attempt to verify the capture and control 

efficiencies of these highly-controlled sources. 
 LIST OF FIGURES (continued) 

Number Page

 24

Option I: 

1.Identify sources with stated control efficiencies greater than 

95 percent. 

2.For these sources, apply the Questionnaire to determine the 

actual RE for the source. If the Questionnaires cannot be 

completed by the November 15, 1992 deadline, an adjustment 

can be made afterwards.6

 In these areas, Option II must be 

used for the November 15, 1992 inventory submittal. 

Option II: 

1.Apply the 80 percent default value for RE to the sources with 

control efficiencies greater than 95 percent in the base-year 

inventory. 

Option III: 

1.Identify sources with stated control efficiencies greater than 

95 percent. 

2.For the 1990 base-year inventory, use option I or II. 

3.After submitting the 1990 base-year inventory, develop an 

alternative questionnaire to determine RE for these highlycontrolled sources. 

4.Obtain EPA approval for the RE questionnaire. 

5.Apply the alternative RE questionnaire to the identified 

sources. 

6.Adjust the base-year emission inventory after the new RE values 

have been calculated for these sources.5

2.7.4.9 Answering the Questionnaires

 The evaluator should complete one point source questionnaire 

for each selected point source in the sample that passes the 

 

6

EPA prefers that adjustments be made prior to the public hearing on the 

inventory, but no later than any other hearing held on the rate of progress 

plan and attainment demonstration (see Memorandum of September 29, 1992, 

Public Hearing Requirements for 1990 Base-Year Emission Inventories for Ozone 

and CO Nonattainment Areas, from John Calcagni and Bill Laxton to Regional Air 

Division Directors). 
 LIST OF FIGURES (continued) 

Number Page

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preliminary screening test and one area source questionnaire for 

each area source category. The questionnaires are designed to be 

answered using available file information only. No dedicated 

source inspections are required. The complete file information 

on a particular source, including reports of previous visits and 

inspections, should be obtained by the evaluator prior to 

answering the questionnaire. To answer the questionnaires, the 

evaluator should confer with the State or local compliance 

inspector most familiar with the source or source category being 

evaluated. If an answer cannot be ascertained, the space marked 

"unsure" should be indicated on the questionnaire. 

 In addition, the evaluator should obtain any information 

relating to potential deviations or deficiencies in the State or 

local regulations. The most helpful information would be in the 

SIP-call follow-up letter sent to the State Air Program Director 

from the corresponding EPA Regional Air Division Director. This 

letter delineates specific deficiencies that EPA required to be 

corrected in response to the SIP-calls for nonattainment areas in 

that State. Another source of information is the document, 

Issues Relating to VOC Regulations, Cutpoints, Deficiencies, and 

Deviations, issued on May 25, 1988 by AQMD. The evaluator should 

confer with the EPA Regional Office to ascertain the most current 

and applicable information on regulation deficiencies. 

2.7.4.11 Determination of Rule Effectiveness Values

 The answers to the questions on the questionnaires each have 

a point value associated with them. After answering each 

question with the most appropriate response, the evaluator should 

sum the point values of the answers for each section and record 

the sub-totals and/or totals in the space provided on the last 

page. Section 3 describes how to apply these RE values in the 

emission inventory. 

 Determination of the RE value for point source categories has 

been revised since the Post-87 RE guideline to make the category 

value more representative. Formerly, a simple arithmetic average 

of the questionnaire totals produced the RE value to be used for 

all sources in that category (i.e., every completed questionnaire 

received equal weight). The former procedure has been replaced 

by a revised, emissions-weighted average to accommodate the true 

effect on category emissions. By using an emissions-weighted 

average, the questionnaire RE value better estimates the effects 

of higher (or lower) RE at large emissions sources on the overall 

category emissions. Where large emissions sources have better 

compliance (RE closer to 100 percent) than small emissions 
 LIST OF FIGURES (continued) 

Number Page

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sources, emissions for the category will more accurately reflect 

the effect of the compliance level of the larger facilities. 

 The questionnaire results should be weighted by uncontrolled

emissions. This weighting system increases the overall influence 

of the estimated RE at larger magnitude emitters on the category 

emissions. The questionnaire results from the surveyed 

facilities should be treated in the following manner: 

 where:n is the number of facilities with completed 

questionnaires 

 Table 2-5 illustrates the use of this equation and the 

calculation of the RE value. The State or local agency may be 

asked by the Regional Office to support RE values calculated from 

the questionnaires. The State or local agency should be prepared 

to document the procedures and information used to complete the 

questionnaires. 

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 LIST OF FIGURES (continued) 

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2.8SSCD STUDY APPROACH

2.9.1 Purpose of the Study

TABLE 2-5. EXAMPLE OF WEIGHTED RE VALUE USING QUESTIONNAIRE 

Facility 

RE from 

Questionnaire 

Uncontrolled

Emissions 

Weight 

Factor1 Weighted 

RE2

RE Value 

for 

Facility3

A 100% 500 0.42 0.42 100%

B 60% 100 0.08 0.05 60%

C 80% 75 0.06 0.05 80%

D 80% 200 0.17 0.13 80%

E 85% 50 0.04 0.04 85%

F 90% 30 0.03 0.02 90%

G 65% 120 0.10 0.07 65%

H 75% 35 0.03 0.02 75%

I 95% 25 0.02 0.02 95%

J 80% 60 0.05 0.04 80%

 

TOTAL 1,195 1.00 0.86 

CATEGORY RE VALUE4 86%

1

Weight factor equals facility's uncontrolled emissions over total 

uncontrolled. 2

Weighted RE equals facility's RE from questionnaire times weight factor. 

3

Use the RE value from the facility-specific questionnaire response for that 

facility. 4

All facilities not included in the survey sample are assigned the category 

value.

 
 LIST OF FIGURES (continued) 

Number Page

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 The purpose of the SSCD study is to provide the States, local 

agencies and EPA with criteria and procedures for conducting an 

RE study or evaluating the degree of source compliance with 

existing rules. In the context of the SSCD study, RE means the 

extent to which a rule actually achieves (or has the capability 

of achieving) desired emission reductions, both in terms of the 

reductions projected for that rule, and the reductions that would 

ordinarily be achieved if the rule were properly implemented. 

Like the questionnaire approach, the SSCD study only applies to 

the geographic area in which it is conducted. In contrast to the 

generic questionnaire approach for both point and area sources, 

each SSCD study is individually designed and applied to a single 

point source category. 

 The principal goals of the SSCD study procedure are: (1) to 

determine the effectiveness of rules for a specific source 

category in a specific nonattainment area according to the 

quantitative criteria set forth in this protocol; and (2) to 

identify specific implementation problems which need to be 

addressed by the State, local and EPA compliance and enforcement 

staff in order to achieve greater RE in the future. 

2.9.3 Summary of the SSCD Study Approach Procedures

 The SSCD study prescribes inspections, emissions tests and 

agency audits to compare actual measured emissions to "allowable" 

emissions under the existing rules(s). The difference represents 

the degree of compliance with the rules (i.e., the RE in 

achieving emissions reductions). The study requires that the 

source sample size from a single source category be determined 

statistically, with considerations given to the allocation of 

personnel for inspections. 

 The SSCD study approach consists of a two-phase study 

including (1) an office investigation and (2) a field inspection 

at the source. Each study initiated by a State or local agency 

must receive approval from the EPA Regional Office and 

Headquarters. In general, the field inspection involves 

determining the compliance status of a representative number of 

sources in a nonattainment area through the calculation of 

emissions and the determination of the percent effectiveness of 

current regulations. Sources included in the study are inspected 

unannounced. The elements of the field inspection include the 

following: (1) rule application evaluation, (2) State inspection 

procedures evaluation, (3) compliance determinations, 

(4) emissions quantification, (5) quality assurance, and 

(6) inventory evaluation. An inspection checklist is developed 
 LIST OF FIGURES (continued) 

Number Page

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and used for each source. The checklist is comprised of three 

sections which are (1) inventory verification, (2) regulatory 

applicability, and (3) inspections procedures evaluation. All 

applicable regulations and policies pertaining to the sources 

under study are identified and the compliance status of the 

sources with SIP rules is determined, differentiating between 

procedural and emission requirements. The office investigation 

phase provides a further analysis of program implementation 

elements not susceptible to a comprehensive evaluation during a 

field inspection. 

 The study identifies problems which can be corrected, 

processes corrective action options, and comments on advantages 

and disadvantages of each option. Within one year following the 

study, a follow-up audit is conducted to determine whether 

corrective actions were implemented. Finally, the SSCD study 

includes an inventory demonstration for the selected source 

category which includes the following elements: (1) field 

investigation follow-ups if inventory discrepancies evolve; and 

(2) a search for potentially omitted sources including a survey 

of source exemption applicability and a ground survey to locate 

unregistered sources. 

2.9.5 Calculating RE from an SSCD Study

 The SSCD study approach may be applied only to a single 

source category for which a given study is designed. The result 

of each study is a category-specific RE estimate for a particular 

geographic area and category. States and local agencies may need 

to determine if previously existing SSCD study results remain 

valid or if the study is outdated due to industry or regulatory 

changes. Only studies deemed valid for the inventory period may 

be used. To apply the result for SIP purposes, the calculation 

must reflect this context. 

 The percentage effectiveness calculations will be based on a 

comparison of actual emissions to the allowable emissions for 

sources included in the study. These emissions must be documented 

as part of the field investigation phase of the study, and the 

calculations must be based on emissions testing, sampling and 

usage data identified for each source during the investigation. 

 Percentage effectiveness for base year inventory applications 

should be calculated according to the procedure listed below. 

Compute separately the total allowable and actual emissions for 

all sources on the day of the inspection or source test. The 

following equation should be used: 
 LIST OF FIGURES (continued) 

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RE Inventory Method (for SIP inventory purposes)
 LIST OF FIGURES (continued) 

Number Page

 31

If the baseline cannot be determined, the following equation, 

which calculates the baseline from allowable emissions and the 

control efficiency, is used: 

 where: 

 Baseline = base year inventory (before control) 

 Actual =emissions determined during course of study from mass 

balance, stack testing, CAA Section 114 

responses, inspections and/or production 

records review 

 Allowable = emissions determined from SIP requirements 

 Control Efficiency = control efficiency defined in the CTG 

•This method considers what emission reductions were actually 

achieved and evaluates performance in terms of the 

magnitude of excess emissions. 

•This method should be applied in any study where the results 

will be used to modify the 80 percent rule effectiveness 

assumption. 

 Users requiring more information should consult SSCD guidance 

on the RE approach. 

________________________ 

6

Control Efficiency calculations are shown in Section 3.2.1.

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2.10USING RESULTS FROM SSCD STUDIES, QUESTIONNAIRES AND THE 

DEFAULT

 The procedural approaches to determine RE using the 

questionnaire and the SSCD study are vastly different. Figure 2-1 

shows a summary comparison of the questionnaire approach 

(Appendices A and B) versus the SSCD study approach. The shaded 

boxes represent common steps. 
 LIST OF FIGURES (continued) 

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 33

QUESTIONNAIRE STEP SSCD STUDY

Identify Personnel to Conduct 

Evaluation 

(1) Select One Point Source Category 

↓ ↓

Select Sources at Random for 

(Statistically Significant 

Sample) Point and Area Source 

Categories 

(2) Identify Personnel to Conduct 

Evaluation 

↑↓ ↓

Perform Screening for Applicable 

Sources 

(Repeat Step (2) as Necessary) 

(3) Develop Appropriate Protocol/ 

Receive Approval from SSCD or 

Region 

↓ ↓

Complete Questionnaire (4) Select Sources at Random 

(Statistically Significant 

Sample) 

↓ ↓

Score Evaluation (5) Office Investigation 

↓ ↓

Determine RE for Each Category (6) Evaluate Current Rule 

Application 

 ↓

 (7) Field Inspections and Testing 

 ↓

 (8) Inventory Accuracy Demonstration 

 ↓

 (9) Calculate Rule Effectiveness 

 ↓

 (10) Report 

 ↓

 (11) Corrective Action Plan 
 LIST OF FIGURES (continued) 

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 The State or local agency may use the questionnaire approach 

or may apply the default value across the entire inventory. Where 

an SSCD study result is used or all source categories are not 

covered by the questionnaires, a combination of methods must be 

used to complete the inventory. Table 2-6 lists the combinations 

available to the State and local agencies when an SSCD study is 

used or the questionnaire approach does not cover all categories. 
 LIST OF FIGURES (continued) 

Number Page

 35

TABLE 2-6. COMBINING SSCD STUDY AND QUESTIONNAIRE 

 APPROACHES 

RE Value Based on... Approach for Other Categories 

SSCD Study Other categories may be analyzed based 

on questionnaires or the 80% default 

value may be applied. 

Questionnaires Remaining categories may use the 80% 

default value provided the minimum 

criteria for applying questionnaire 

defined in Section 2.4.2.3 are met. 
 LIST OF FIGURES (continued) 

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 SECTION 4 

APPLICATION OF RULE EFFECTIVENESS IN BASE YEAR INVENTORIES

5.1INTRODUCTION 

 This section provides guidance on the application of RE to 

emissions inventories and presents the emissions calculation 

procedure. RE must be applied to base year SIP inventories for 

ozone precursors and CO, specifically to sources of VOC, NOx and 

CO. Previous SIP inventories considered only VOC and the majority 

of current applications will still be for VOC sources. (Since few 

emission regulations for non-mobile sources of NOx and CO existed 

in 1990, RE is currently not an issue for these pollutants for 

base year 1990 inventories. If these pollutants are regulated in 

the future, RE will need to be applied in subsequent inventories.) 

 RE factors are to be applied for the purpose of more 

accurately representing actual emissions. While local RE values 

may be determined on a source category basis, these same factors 

should be applied in the inventory on a source-by-source basis. 

Applying RE factors to individual sources will increase the 

emissions indicated for most sources; therefore, it is important 

for air pollution control specialists to understand that the RE 

estimates determined by the above procedure are to be used for 

emission inventory purposes only. 

5.3CALCULATING RULE-AFFECTED EMISSIONS

 Determination of rule-affected emissions requires three 

inventory data elements: (1) the RE value (percent); (2) overall 

control efficiency; and (3) estimated uncontrolled emissions. 

Before applying RE, the relevant sources must be identified as 

described in Section 2. Once an RE percentage has been determined 

for each source category and a source has been determined to be 

subject to RE, the emissions from that point or area source are 

adjusted. If the questionnaire approach was used, apply the 

individual questionnaire RE scored for sources surveyed by the 

questionnaire; apply the calculated category RE value to the 

sources in the category which were not surveyed. The calculation 

is done source by source at the emissions calculation step 

(typically the segment or process level in the Aerometric 

Information Retrieval System (AIRS) for point sources and category 

by category for area sources. 

 The following equation is used to calculate rule-affected 

emissions: 
 LIST OF FIGURES (continued) 

Number Page

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where RE and control efficiency are expressed as fractions. The 

equation clearly demonstrates that RE accounts for the 

effectiveness of the control. 

 Section 2 discussed the derivation of the RE value. Control 

efficiency and uncontrolled emissions are typical emissions 

inventory elements. Uncontrolled emissions may have to be 

backcalculated from the estimated controlled emissions. For 

example, source tests may account for the control in place. 

Control efficiency is a required SIP data element for control 

devices, but control efficiency for RE includes both physical and 

regulatory controls. 

5.4.1 Control Efficiency

 Regulatory controls are emissions limits implemented through 

either regulatory or physical means. A solely regulatory control 

is typically an emission rate limitation unrelated to a control 

device. For example, an industrial coating operation may be 

limited to using a coating of no more than 2.0 lbs VOC per gallon 

coating. The control efficiency is based on the difference 

between the total solvent used prior to the regulation and postregulation. 

 A physical control is a control device such as an incinerator 

or carbon adsorber used to reduce emissions from a process. 

Control efficiency may be reported on the basis of manufacturer's 

specifications or emissions testing. To be reliable, capture 

efficiency, actual operating conditions and process and/or device 

upsets must be included when estimating emissions. These 

variables may be factored into a single average control efficiency 

or emissions may be estimated for each different operational mode 

(refer to emission inventory guidance). 

 Application of the RE value is straightforward where the 

control is a physical device (e.g., a carbon adsorber) with an 

estimated efficiency (e.g., 95 percent). When the control is due 

to a rule implementation (e.g., coatings restricted to no more 

than 3 lbs VOC per gallon), it is more difficult to determine the 

"control efficiency" of that rule. However, there is no 

distinction between regulatory and physical controls for the 

purpose of applying RE. 

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 EPA recognizes that a control efficiency inherent in a 

regulation (e.g., an emission limit such as lbs VOC per gallon 

coating) may be difficult to determine. In these cases the best 

option is to determine emissions before and after a regulation was 

adopted from existing source records. This may be impossible if a 

source was never in operation or inventoried prior to rule 

adoption or if process changes have made such comparisons 

meaningless. A second option is to use the control efficiency 

estimate used in the development of the CTG or State/local rule. 

 Questions have been raised regarding the control provided by 

rules specifying types of storage tanks for petroleum product 

storage. The best way to calculate control efficiencies for 

storage tanks is to calculate emissions per unit product based on 

the AP-42 equations before (e.g., a fixed-roof tank) and after 

(e.g., an external floating roof tank) rule adoption. This course 

may be both resource and time intensive. Representative control 

efficiencies for gasolines and distillate oil from Table 3-1 may 

be used instead of detailed, tank-by-tank calculations. These 

values have been derived based on a wide variety of tank sizes and 

throughputs which indicate that emissions per unit product from a 

tank type are principally dependent on the vapor pressure of the 

contents, not tank size.1
 LIST OF FIGURES (continued) 

Number Page

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 Where a regulatory or inherent control efficiency must be 

determined to apply RE, the inventory preparer should consider and 

use the procedures listed below to make this determination. These 

procedures are listed in order of preference and reliability: 

1)Make a "before and after regulation" determination based on 

historical inventory records for each affected source or 

the category. 

2)If (1) is not possible, refer to the local SIP development 

documentation that supports the planned or expected 

control level anticipated from the regulations(s) 

applicable to the category. Use this control level as the 

control efficiency for sources covered by the rule(s). 

 TABLE 3-1. DEFAULT PETROLEUM STORAGE TANK 

 CONTROL EFFICIENCIES

Material 

Stored 

Before Rule 

Condition 

After Rule 

Condition 

Default 

Control 

Efficiency 

Gasoline RVP7 to 

RVP10 

Fixed Roof External 

Floating Roof 

95% 

Distillate No. 2 Fixed Roof External 

Floating Roof 

91% 

 

Gasoline RVP7 to 

RVP10 

Fixed Roof Internal 

Floating Roof 

98% 

Distillate No. 2 Fixed Roof Internal 

Floating Roof 

92% 

 

Gasoline RVP7 to 

RVP10 

External 

Floating Roof 

Internal 

Floating Roof 

60% 

Distillate No. 2 External 

Floating Roof 

Internal 

Floating Roof 

20% 
 LIST OF FIGURES (continued) 

Number Page

 34

3)As a final resort, refer to Appendix E to estimate the 

expected control effectiveness for CTG categories. This 

listing has been developed from CTG summaries and is only 

to be used to approximate control efficiencies for RE 

application where no other data are available. This 

listing presents ranges in some cases; use the lower end 

of the range unless other justification can be documented. 

 Where the upper end of the range is 100 percent, this 

value cannot be used except where direct determination or 

irreversible process change can be documented. EPA has 

not determined the validity or reliability of these 

control efficiencies for this purpose.

5.4.3 AIRS Coding

 The AIRS/Facility Subsystem (AFS) and the AIRS Area and Mobile 

Source (AMS) are capable of storing RE values and applying RE to 

the point and area source inventories, respectively. The 

procedure involves setting the "SIP Rule in Place" field to "Y," 

"B," "M" or "R." These codes designate Yes, BACT, MACT and RACT, 

respectively. [Note: While the field is called "SIP Rule in 

Place," this refers to any rule that is in place in the inventory 

area that is expected to reduce emissions, regardless of whether 

or not the rule is part of the SIP.] Any source with these codes 

and a nonzero control efficiency will be expected to have an RE 

value. (Remember that directly determined emissions sources have 

a 100 percent RE.) For emissions calculated using an emission 

factor, process or throughput rate, and control efficiency, AIRS 

can automatically calculate the RE emissions adjustment. Outside 

the AIRS system, these calculations will have to be performed as 

previously described. 

 When coding AIRS or other inventory transactions, all 

regulated sources where the regulation has an impact on the 

estimated emissions should have an RE entry in the estimated 

emissions. State and local agencies should code RE values 

according to the type of sources (Table 3-2): 

•For sources making no attempt at compliance, RE should be 0 

percent 

•Directly determined or irreversible processes that eliminate 

solvent (VOC) emissions should be coded as 100 percent 
 LIST OF FIGURES (continued) 

Number Page

 35

•All other regulated sources should be coded with a value between 

0 and 100 percent 

5.5DOCUMENTING RULE EFFECTIVENESS FOR THE SIP SUBMITTAL

 Rule effectiveness must be documented in the SIP inventory 

submittal, consistent with OAQPS Emissions Inventory 

Requirements,2,3 the Quality Review Guidelines,4

 and the individual 

Inventory Preparation Plans (IPPs). These requirements include a 

discussion of how rule effectiveness was incorporated into the 

inventory. States should clearly annotate summary emissions 

tables as either adjusted or unadjusted for rule effectiveness. 

Emission estimates will be reviewed to ensure appropriate 

application of Rule Effectiveness in the base year inventories. 

Any deviations from OAQPS guidance on RE should be discussed in 

the submittal. 

 TABLE 3-2. CODING RE IN ELECTRONIC INVENTORY SUBMITTALS 

RE Determination Coded RE Value

Uncontrolled Source 0% 

Irreversible Process 

Change 

100% 

Direct Determination 100% 

Questionnaire Weighted score from questionnaire 

(%) 

SSCD Study Study results using SIP inventory 

calculation (%) 

Default 80% 
 LIST OF FIGURES (continued) 

Number Page

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5.7REFERENCES

1.Memorandum from David Winkler and David Zimmerman, TRC 

Environmental Corporation, to Gerri Pomerantz, Office of Air 

Quality Planning and Standards, U.S. Environmental Protection 

Agency, "Control Effectiveness: Petroleum Product Storage 

Tanks." August 13, 1992. 

2.U.S. Environmental Protection Agency, Emission Inventory 

Requirements for Ozone State Implementation Plans, EPA-450/4-

91-010, Office of Air Quality Planning and Standards, Research 

Triangle Park, NC, March 1991. 

3.U.S. Environmental Protection Agency, Emission Inventory 

Requirements for Carbon Monoxide State Implementation Plans, EPA-450/4-91-011, Office of Air Quality Planning and 

Standards, Research Triangle Park, NC, March 1991. 

4.U.S. Environmental Protection Agency, Quality Review Guidelines 

for 1990 Base Year Emission Inventories, EPA-454/R-92-007, 

Office of Air Quality Planning and Standards, Research 

Triangle Park, NC, August 1992. 
 LIST OF FIGURES (continued) 

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SECTION 3 

EXAMPLE CALCULATIONS

 The following examples illustrate how to include RE in the 

emissions calculations for several types of facilities. Most of 

these examples are presented on a daily emissions basis. 

Typically, emissions are first calculated on an annual basis. RE 

actually applies to both annual and daily estimates; EPA emission 

inventory guidance discusses the calculation of daily estimates 

from annual estimates. 

4.1POINT SOURCES

4.2.1 Bulk Terminals (Loading Racks) 

Calculation based on a device control efficiency and RE 

questionnaire results.

 A petroleum products bulk terminal distributes motor gasoline 

and distillate fuels (heating oils, etc.). In 1990, the facility 

distributed 110,000,000 gallons of gasoline and 54,000,000 

gallons of distillate fuels. The loading racks used to transfer 

the fuels use refrigerated vapor recovery units (RVUs) to control 

emissions. The control efficiency for RVUs is greater than 90 

percent as determined by an approved EPA method. The equipment 

is checked annually unless obvious problems require earlier 

inspections, and records of all repairs are maintained for agency 

review. The facility is inspected triennially, with the most 

recent inspection occurring 3 years ago. Emission factors for 

gasoline and distillate fuel loading loss have been determined to 

be 8.5 and 0.02 pounds VOC per thousand gallons, respectively. A 

questionnaire was completed for this facility and a RE of 78 

percent was estimated for this facility (overall 82 percent for 

the category). What emissions should be reported for this 

facility?

Answer:Compute the loading losses for gasoline and distillate. 

Emissions are based on emission factors and therefore 

must include RE. Use the facility-specific RE rather 

than the category estimate. 
 LIST OF FIGURES (continued) 

Number Page

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Base Data for Loading Losses 

 Gasoline Distillate 

Throughput (gallons) 110,000,000 54,000,000 

Emission Factor 8.5 lbs VOC/103 gal 0.02 lbs VOC/103 gal 

Control Efficiency 

(AP-42) 

>90% >90% 

Rule Effectiveness 78% 78% 

A. Gasoline Loading Losses 

B. Distillate Fuel Loading Losses 

C. Total Emissions (from Loading Losses) 

4.2.3 Beverage Can Coating

Calculation based on an effective control efficiency in the 

absence of a control device, solids equivalency 

determination and RE questionnaire results.

 A beverage can coater has been required to use high-solids 

coatings for its interior can coating. The plant personnel 

follow a weekly maintenance routine. The facility was last 

inspected in June for compliance evaluation, with the last 

previous inspection occurring three years ago. The following 

coating and process characteristics have been determined. 

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 The coater previously used 50 gallons per day of interior can 

coating. The coating had a density of 9 pounds per gallon. The 

coating was 60 percent solvent (by weight); the solvent was 100 

percent VOC with a density of 8 pounds per gallon. The coater is 

required to use a new coating that does not exceed 3 pounds of 

VOC per gallon of coating. The manufacturer reports a density of 

10 pounds of coating per gallon of reformulated coating. No 

change in production volume of coated cans has occurred, but the 

coating consumption (in gallons per day) is not reported in this 

year's inventory. This facility was not included among the 

questionnaires, but the category average RE is 84 percent. What 

emissions should be reported in the inventory?

Answer:In most categories, control efficiencies and RE are 

applied to uncontrolled plant emissions resulting in RE 

emissions. Since the end result of coating is the 

application of the solid fraction of the coating, control 

efficiencies for coatings are calculated as the reduction 

in emissions related to the coating solids only. Thus, 

the first step in estimating the control efficiency for 

this example is to estimate VOC emissions per volume of 

solids. 

Old Coating

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New Coating

Now that the emissions rates per gallon of solids have been 

determined, the control efficiency and emissions may be 

determined. 

(This is an illustrative case. In an actual inventory, 

emissions from the exterior coating would also be 

calculated.) 

4.2.5 Paper Coating Facility

Calculation based on direct determination of emissions.

 A paper coater uses only coatings specified by the 

manufacturer to contain 2.9 pounds VOC per gallons, less water, 

to comply with the RACT limit. Coating usage at the plant is 

documented to be 100 gallons, less water, per day and no 

additional solvents are used. This information was confirmed 

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during the annual inspection. The RE for this source category 

has been determined to be 70 percent based on the RACT reduction 

calculated for the category. What emissions should be reported 

in the inventory?

Answer:Emissions from this plant can be calculated by means of a 

direct determination, because the solvent concentration 

is determined based on the manufacturer's specification 

and the coating use is documented daily, thus RE does not 

need to be applied. 

4.2.7 Metal Furniture Coating

Calculation based on transfer and control efficiencies and 

the default RE value.

 A large metal furniture manufacturer applied 326 gallons of 

coating solids on its furniture each day (i.e., it actually 

sprays more, but only 326 gallons of solids are actually 

deposited on the products). The coating it uses contains 35 

percent by volume solids (65 percent VOC). The solvent used 

weighs 7.33 pounds per gallon. The facility uses high-volume, 

low-pressure (HVLP) spray equipment to achieve an 85 percent 

transfer efficiency (TE). The facility has also installed RACT 

to achieve an estimated 82 percent emissions reduction. The 

default RE has been applied to this source category (80 percent). 

What emissions should be reported in the inventory?

Answer:Uncontrolled emissions should be determined by calculating 

the amount of coating solids applied and the amount of 

coating applied. Controlled emissions are based on the 

RACT emissions reduction and the default RE. 

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4.2.9 Automobile Assembly Plant

Calculation based on a device control efficiency, and 

solvent-use recordkeeping and RE questionnaire results. 

 An assembly plant that coats automobile parts uses 150 

gallons per day of coatings containing 5.5 pounds VOC per gallon. 

 An additional 10 gallons of solvent, with a density of 7.1 

pounds VOC per gallon, is used for cleanup each day. Emissions 

are controlled by a carbon adsorber that demonstrated a 90 

percent capture and control efficiency during a recent test. The 

plant keeps substantial records of coating and solvent usage, but 

no data on control device operation and/or maintenance (O&M). 

The RE for this source category has been determined to be 75 

percent based on questionnaire responses. What emissions should 

be reported in the inventory?

Answer:It may appear that emissions can be calculated by means of 

a direct determination due to the good coating and 

solvent records at the source. However, the presence of 

a control device precludes direct determination of 

emissions. Therefore, RE needs to be included in the 

emissions calculation. 

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4.2.11 Large Appliance Coating

Calculation based on an irreversible process change and 

direct determination of emissions.

 An appliance manufacturer uses 1,200 pounds of a powder 

coating per day. The coating is applied with electrostatic spray 

equipment achieving a transfer efficiency of 95 percent. The 

company also uses 10 gallons of solvent with a density of 

7.1 pounds VOC per gallon solvent for daily cleanup operations. 

The plant keeps detailed records of coating and solvent use. The 

RE for this source category has been determined to be 75 percent. 

What emissions should be reported in the inventory?

Answer:Powder coating is an irreversible process change, but the 

cleanup solvent emissions must be calculated.7

 Since 

there are no controls for the cleanup solvent, but 

adequate records are kept, a direct determination of 

emissions can be made: 

4.2.13 Large Petroleum Dry Cleaner

Calculation based on the expected rule control efficiency, 

reported controlled emission and the default RE value.

 A large petroleum dry cleaner has an estimated controlled 

emission rate of 200 tons of VOC per year. The RACT control 

level is 80 percent based on analysis of the rule for the 

nonattainment area. The plant is in operation 310 days per year. 

 All inventory categories have been assigned the 80 percent 

default RE value. What emissions should be reported in the 

inventory?

Answer: Emissions should be calculated as follows: 

 

7

Powder coating may not always be an irreversible change; the state or local 

agency should make this determination. 

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4.2.15 Graphic Arts

Calculation based on multiple sources at one facility, with 

and without controls. 

 A printing manufacturer uses two gravure lines at a given 

facility. The first gravure line (line 1) was uncontrolled in 

1990 and did not comply with SIP rules at that time; the second 

gravure line was controlled by a fume incinerator meeting the 

State SIP rule. (Line 1 was subsequently upgraded in 1991 to 

include fume incineration). Plant personnel are required to 

complete a formal training program on operation and maintenance 

and follow maintenance guidelines daily. The facility was found 

out of compliance during the past year due to incineration 

failure but was back in compliance within 72 hours. A violation 

notice was placed into the State Agency files. The facility is 

inspected annually. The device control efficiency for fume 

incineration was determined to be 95 percent during the previous 

compliance test. Following a survey using the questionnaire, RE 

for graphic arts was calculated to be 85 percent. 

 For line process, 25,000 pounds of ink (12 percent VOC by 

weight) were used. Other solvents used for viscosity adjustment 

and cleaning totalled 100,000 pounds (100 percent VOC). A total 

of 900,000 pounds of ink (60 percent VOC by weight) were used in 

line 2, while 600,000 pounds of other materials (100 percent of 

VOC) were used for Line 2. The ink consumption is tracked daily 

at the press and the VOC content is given by the manufacturer. 

What are the annual emissions from this facility with Rule 

Effectiveness?

Answer:The two gravure lines must be treated separately. Line 1 

had no controls and RE zero because there was no attempt 

at compliance. The second gravure process (Line 2) is 

controlled and RE must be applied. For comparison, 

facility emissions with and without RE are presented. 

A. Line 1 Gravure Process (No Controls)

 1. Ink Emissions: 

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 2. Emissions for Other Solvents: 

 3. Line 1 Emissions: 

B. Line 2 Gravure Process 

Step 1 - Before Rule Effectiveness 

 1. Ink Emissions: 

 2. Emissions from Other Solvents: 

 3. Line 2 Emissions (Before Rule Effectiveness) 

 Gravure Process (Emissions Accounting for RE) 

C. Facility Emissions 

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4.3AREA SOURCES

4.4.1 Stage I (Area Source Category)

Calculation based on rule penetration and SSCD study results.

 The gasoline throughput for service stations in a 

nonattainment area is reported to be 400,000 gallons gasoline per 

day. The uncontrolled Stage I emissions are estimated to be 11.5 

pounds VOC per 1,000 gallons. The State regulation requires 95 

percent control at each facility and covers about 90 percent of 

the overall emissions from the category (i.e., rule penetration = 

90 percent). The RE for this category has been determined to be 

60 percent following an SSCD study conducted by the State agency. 

What emissions should be reported in the inventory?

Answer:RE and penetration should be introduced into the emissions 

calculation as follows: 

4.4.3 Architectural Coating (Area Source Category)

Calculation based on direct determination of emissions.

 The ozone nonattainment area inventory includes architectural 

surface coating as an area source category. Architectural 

coatings include surface coating, painting and decorating of 

architectural structures using water-based and oil-based 

coatings, cleanup solvents and thinners. The agency describes 

the following inventory method and emissions data for the 

category. 

 Architectural surface coating use (consumption) in the 

nonattainment area is based on a comprehensive survey of all 

coating manufacturers and marketers in the nonattainment area. 

The survey results provided consumption of each type of 

coating/solvent/thinner and the manufacturers' statement of its 

solvent content. The survey results are from 1990 and include 

all coatings, thinners and solvents used in the category. 

Results are an annual weighted composite VOC emission expressed 

as pounds VOC per gallon coating (0.46 pounds VOC per gallon) and 

an estimate of 1,555,322 gallons of coating used in the 

nonattainment area. What emissions should be reported in the 

base year inventory and what RE value should be applied? 

Answer:Although applied to an area source category, this example 

follows the traditional point source interpretation of 

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direct determination because it provides (1) an 

accounting of consumption and (2) use of a known solvent 

content. However, the inventory procedures are entirely 

different for area source categories. In this example, a 

direct determination is based on the mass balance done 

for the nonattainment area. 

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y 

 APPENDIX A 

 RULE EFFECTIVENESS QUESTIONNAIRE 

POINT SOURCES
 LIST OF FIGURES (continued) 

Number Page

 A-2

 RULE EFFECTIVENESS EVALUATION FORM

 Point Sources

Source Category 

Source Name 

Source Location 

 Source Identifier 

 

 Choose the one most appropriate response for each question. 

Answers should be confirmed by information in the State or local 

agency's files. When the questionnaire has been completed, total 

the scores to determine RE for the source; the average score for 

all evaluated sources in a category is the RE for that category. 

Preliminary Screening:

1.Is this source currently uncontrolled? No 

Yes 

(If "yes", choose another source to evaluate, and indicate a RE of 

0 percent for this source in the inventory.) 

2.Are emissions from this source controlled No 

 by an irreversible process change? 

Yes 

(If "yes", choose another source to evaluate, and indicate a RE of 

100 percent for this source in the inventory.) 

3.Have emissions from this source been No 

 calculated by means of a direct determination? 

Yes 

(If "yes", choose another source to evaluate, do not apply RE to 

this source, and indicate a RE of 100 percent in the 

inventory.)8

A. Nature of the Regulation

1.Does the regulation contain uncorrected deficiencies (not 

including record keeping deficiency) as specified in the 

 

8

If a source's emissions have been estimated using direct determination, 

maintain the supporting data and calculations in your files. 
 LIST OF FIGURES (continued) 

Number Page

 A-3

SIP-call follow-up letter from the EPA Regional Air 

Division Director to your State Air Program Director? 

 No (5) Yes or unsure (0) Score 
 LIST OF FIGURES (continued) 

Number Page

 A-4

2.Does the State require source to keep records sufficient to 

enable an inspector to determine compliance status? 

 Yes (5) No or unsure (0) 

Score 

3.How complex is the determination of compliance? (If State can 

verify through detailed records that all necessary 

compliance determination procedures have been carried out, 

score 5 points for this question regardless of answer 

checked below.) 

 Determination can be made by looking at 

 facility, as in the case of an equipment 

 standard. (5) 

 Determination can be made by collecting 

 and analyzing one sample or by evaluating 

 continuous emission monitoring reports. (4) 

 Stack testing, including capture and 

 control, must be performed to determine 

 compliance. (3) 

 Determination requires that multiple 

 samples be taken and analyzed and that 

 plant records be evaluated, as in the case 

 of cross-line averaging, time averaging, 

 or other bubbles. (2) 

 Score 

B. Nature of Procedures Used to Comply With Regulation

1.This question concerns the relative level of confidence in the 

long-term performance capabilities intrinsic to different 

control techniques (e.g., how time in operation and 

maintenance degradation might affect emissions control). 

(Check each technique used at the facility, total the 

scores assigned to each control, divide by the number of 

controls and report the average as a single score. If 

State can verify through detailed records that the source 

has actually been in continuous compliance at all times 

during the past two years, score 10 points on this 

question regardless of control methods used.) 

 Floating roof (10) 

 Thermal incinerator (8) 

 Vapor balance (8) 

 Reversible process change (e.g., coating 
 LIST OF FIGURES (continued) 

Number Page

 A-5

 reformulation) (8) 

 Condensation system (7) Carbon adsorber (7) Catalytic incinerator (7) Other (assign point value < 10, as 

 appropriate, relative to above controls) (_) 

 Score 

2.Are fugitive emissions that might cause noncompliance a 

possibility where add-on controls are used (check one)? 

 No or not applicable because 

 there is no add-on equipment (5) 

 No, because they have been shown by 

 an EPA-approved capture efficiency 

 test to be below allowable limits and 

 to be so on a continual basis (5) 

 Yes or unsure (0) 

 Score 

C.Performance of Source in Complying With Regulation

 

1.What procedures does the source follow for operation and 

maintenance (O&M) of the control equipment (check one)? 

 Plant personnel complete a formal 

 training program and follow daily 

 written instructions for O&M (5) 

 Same as above, except no training (4) Plant personnel follow weekly 

 established O&M routine (3) 

 Equipment is assumed to be operating 

 correctly unless major malfunction 

 is detected (1) 

 Score 
 LIST OF FIGURES (continued) 

Number Page

 A-6

 2.What is the nature of self-monitoring efforts conducted by 

the plant to assess compliance (check one)? 

 Source test (using EPA-approved 

 method)9 is 

conducted annually (5) 

 Sample analysis (using EPA-approved 

 method)10 is conducted for each ink 

 or coating used (5) 

 Above tests are performed, but 

 less frequently (3) 

 None or unsure (0) 

 Score 

3.Does the plant keep records of data (including self-monitoring, 

O&M, coating usage, etc.) that would allow verification of 

compliance? 

 Yes (5) No or unsure (0) 

Score 

 4a.Has source been found to be out of compliance in the last 

12 months? (If "yes", then answer question 4b; otherwise, 

skip to Part D) 

 No (10) Yes or unsure (0) 

Score 

 4b.In responding to Notices of Violation, did the source 

demonstrate compliance within the required time frame? 

(Answer this question only if you answered "yes" to 

question 4a. above) 

 Yes (5) 

 No or unsure (0) 

Score 

 

9

For examples of approved test methods, see "Test Methods or Procedures for 

Group I, II, and III CTG's," Issues Relating to VOC Regulations, Cutpoints, 

Deficiencies, and Deviations, EPA/OAQPS/AQMD/OCMPB/PIS, May 25, 1988. 

10Ibid. 
 LIST OF FIGURES (continued) 

Number Page

 A-7

D.Performance of Implementing Agency in Enforcing Regulation

1.Please answer the following questions regarding verification of 

the source's compliance? 

 a. Are all permits and abatement orders 

 available? No (0) Yes or not applicable (2) 

 Score 

 b.Are all applicable requirements identified 

 in the permit (e.g., emission limits, 

 averaging times, compliance schedule, 

 monitoring, recordkeeping, reporting, 

 operation and maintenance, test 

 requirements)? No (0) Yes or not applicable (2) 

 Score 

 c.Are accurate and complete flow diagrams 

 available for the emission points and 

 control, capture, ventilation and process 

 systems? No (0) Yes or not applicable (2) 

Score 

 d.Are all source test and sample analysis results available? No (0) Yes or not applicable (2) 

Score 

 e.Are all appropriate control system 

 operating data available? No Yes or not applicable (2) 

 Score 

 Total Score 
 LIST OF FIGURES (continued) 

Number Page

 A-8

2.What is the professional background of the person who most 

frequently inspects this source? (Choose the one most 

applicable answer with highest score.) 

 Has > 3 years of experience in 

 conducting plant inspections (5) 

 Has engineering degree and has completed 

 formal training program on how to 

 conduct plant inspections (4) 

 Has engineering degree (3) Has completed formal training program 

 on how to conduct plant inspections (3) 

 No training, < 3 years of experience, 

 and no engineering degree (0) 

 Unsure (0) 

 Score 

3.How many times has source been inspected in the past 24 months? 

 (Inspections must be confirmed by inspection reports in 

implementing Agency's file.) 

 >2 times, unannounced (10) Once or twice, unannounced (8) Once or more, with prior notice or unknown 

 if notice given (6) 

 None or unsure (0) 

 Score 

 4.What was the highest level of inspection performed at the 

source in the last 24 months? (This must be confirmed by 

inspection reports in the implementing agency's file.) 

 Level 4: sampling inspection including 

 preplanned sample collection (5) 

 Level 3: compliance evaluation (4) 

 Level 2: walk-through (2) 

 Level 1: observation from outside (1) 

 None or unsure (0) 

 Score 

 5.Does the agency generally determine compliance by the 

method(s) specified in the regulation? 

 Yes (5) 

 No or unsure (0) 

Score 
 LIST OF FIGURES (continued) 

Number Page

 A-9

 6.If this source has been found out of compliance within the 

last 12 months, has formal documented enforcement action 

(e.g., consent decrees, variances, court actions, 

penalties) been taken against the source? 

 Not applicable because source has not 

 been found out of compliance (5) 

 Yes (5) No or unsure (0) 

 Score 

 7.If source has been found out of compliance within the last 

12 months, has a follow up inspection been made to affirm 

compliance? 

 Not applicable because source has not 

 been found out of compliance (5) 

 Yes (5) No or unsure (0) 

 Score 

SCORING: 

A: ____ of 15 B: ____ of 15 C: ____ of 25 D: ____ of 45 

TOTAL SCORE = of 100 points maximum = RE value for 

source 
 LIST OF FIGURES (continued) 

Number Page

 APPENDIX B 

 RULE EFFECTIVENESS QUESTIONNAIRE 

 AREA SOURCE CATEGORIES
 LIST OF FIGURES (continued) 

Number Page

 B-2

 RULE EFFECTIVENESS EVALUATION FORM

 Area Source Categories

 Source Category 

 Location 

 Choose the one most appropriate response for each question. 

Answers should be confirmed by information in the State or local 

agency's files. When the questionnaire has been completed, total 

the scores to determine RE for the category. 

1.Does the regulation contain uncorrected deficiencies as 

specified in the SIP-call follow-up letter from the EPA 

Regional Air Division Director to the State Air Program 

Director? 

 _____ No (5) 

 _____ Yes or unsure (0) 

 Score ______ 

2.What has been the nature and extent of source education on 

requirements of the regulation? (Check all that apply and 

sum scores.)

 ____ Individual source mailings on compliance 

 requirements (7) 

 ____ Educational opportunities for 

 plant personnel (7) 

 ____ General notices in newspapers, trade 

 journals, etc. (3) 

 ____ Inform trade association (3) 

 ____ None (0) 

 Score ______ 

3.What percentage of sources in the inventory typically are spot 

checked annually (check one)? 

 ____ >30 percent (20) 

____ 10-30 percent (15) 

 ____ 5-9 percent (10) 

 ____ 1-4 percent (5) 
 LIST OF FIGURES (continued) 

Number Page

 B-3

 ____ <1 percent or don't know (0) 

 Score ______ 
 LIST OF FIGURES (continued) 

Number Page

 B-4

4.What percentage of the past year's spot checks indicated 

compliance (check one)? 

 ____ 100 percent (30) 

 ____ 90-99 percent (25) 

 ____ 50-89 percent (20) 

 ____ 25-49 percent (10) 

 ____ 1-24 percent (5) 

 ____ <1 percent or don't know (0) 

 ____ Not applicable since no spot checks 

 were done (0) 

 Score ______ 

5.Has formal documented enforcement action been taken against 

sources found to be out of compliance (check one)? 

 ____ Not applicable since no inspected 

 sources have been found to be out 

 of compliance (10) 

 ____ Yes, for all noncomplying 

 sources (10) 

 ____ Yes, in 50 to 99 percent of the cases (5) 

 ____ Yes, in < 50 percent of the cases (2) 

 ____ Never, or don't know (0) 

 Score ______ 

6.Have enforcement actions for sources in this source category 

been publicized in the media (newspaper, TV, radio, trade 

journals), either through news stories or paid advertisements 

(check one)? 

 ____ Not applicable since no inspected sources 

 have been found to be out of compliance (5) 

 ____ Yes, in every case (5) 

 ____ Yes, in 50 to 99 percent of the cases (3) 

 ____ Yes, in < 50 percent of the cases (1) 

 ____ Never, or don't know (0) 

 Score ______ 

7.Have follow-up inspections been made on sources which were 

found to be out of compliance (check one)? 

 ____ Not applicable since no inspected sources 

 have been found to be out of compliance (10) 

 ____ Yes, in 100 percent of the cases (10) 

 ____ Yes, in 50 to 99 percent of the cases (5) 
 LIST OF FIGURES (continued) 

Number Page

 B-5

 ____ Yes, in < 50 percent of the cases (2) 

 ____ Never, or don't know (0) 

 Score ______ 

 TOTAL SCORE: _________ = RE for Area Source Category 

 (100 points maximum) 
 LIST OF FIGURES (continued) 

Number Page

 APPENDIX C 

 DIRECT DETERMINATION EXAMPLE
 LIST OF FIGURES (continued) 

Number Page

 C-2

 DIRECT DETERMINATION EXAMPLE

 The following wood furniture coating scenario illustrates 

typical emission inventory information that may be collected in 

the surface coating category. This type of information is used 

to make and support a direct determination of emissions for an 

ozone base year SIP inventory.

FACILITY: RITEWAY FURNITURE 

 100 Commerce Drive 

 Ozoneville, USA 

DESCRIPTION

 Riteway Furniture fabricates and paints oak furniture. The 

plant uses high VOC stains, lacquers, glazes and sealers. This 

source is covered under the State's applicable RACT rules for 

wood furniture surface coating. Some of their lines have already 

been converted to high volume, low pressure (HVLP) spray guns. 

On average, their coatings range from 5.67 lbs VOC/gallon coating 

to 6.2 lbs VOC/gallon coating. The State air agency has 

recommended that other lines be converted to HVLP spray guns and 

that average coating solvent content be capped at 6.0 lbs VOC 

(monthly average) for their forthcoming permit amendment. 

EMISSION SOURCES

 1990 

 POINT PROCESS CONTROL DEVICE THROUGHPUT

 SB-1 Paint Spray Booth None (see attached 

 SB-2 " None sheets) 

 SB-3 " None 

 SB-4 " None 

 SB-5 " None 

ADDITIONAL INFORMATION

 The facility summarizes and submits monthly summary data to 

the State. Coating and solvent usage (including thinners and 

cleanup) are tracked as used at the booths, but the spray booths 

are not counted separately. The facility was inspected in 1990 

and the monthly summaries were consistent with their daily 

records on file at the plant, according to the State compliance 

enforcement. 

 The attached sheet is a monthly spreadsheet from Riteway; all 

twelve are on file at the State agency. The "LBS VOC/GAL" come 

from manufacturer's specifications for the coatings. 
 LIST OF FIGURES (continued) 

Number Page

 C-3

ANSWER:There is sufficient information for direct determination 

of emissions because the amount of each coating and 

thinner/cleanup solvent used is tracked and documented 

regularly for each coating/solvent, the VOC content of 

these coatings has been provided by the manufacturer and 

the amount emitted is a mass balance calculation based on 

these data. In this instance, 100% emission has been 

assumed. The facility would be expected to document any 

claims that less than 100% is emitted (e.g., some VOC is 

incorporated into the product.) 
 LIST OF FIGURES (continued) 

Number Page

 C-4

RITEWAY FURNITURE: JANUARY 1990 EMISSION REPORT 

MFG NUMBER 

DESCRIPTION 

A 

LBS/ 

GAL 

B 

LBS VOC/ GAL 

(less water) 

C 

GAL 

USED 

B*C 

LBS VOC 

EMITTED 

S3-4100 ENGLISH SAP STAIN 6.82 6.81 0.00 0 

S7-4057 ANTIQUE ASH SAP STAIN 6.62 6.61 56.00 370 

PSA7-2460 OAK/KORN IND. 7.35 7.03 0.00 0 

P1-3262 WHITE PRIMER 8.26 6.02 190.00 1,144 

PC3-888 ANTIQUE TONER 6.83 6.53 90.00 588 

PC7-935 ENGLISH TONER 6.98 6.53 10.00 65 

PC8-870 BLUE TONER 7.73 6.41 65.00 417 

LS-1582 LACQUER SEALER 7.38 6.05 92.00 557 

LS-1728 WASHCOAT 7.10 6.51 30.00 195 

PC-1006 PENETRATING WOOD SEAL 7.10 6.51 0.00 0 

T-636 MAK 6.81 6.81 0.00 0 

WS-2196 CLEAR GLAZE 7.62 4.28 20.00 86 

WS5-3503 ASH WIPING STAIN 7.58 4.98 15.00 75 

WS7-2589 ANTIQUE GLAZE 8.74 3.88 55.00 213 

WS7-3303 OAK/KORN IND. 8.92 3.64 5.00 18 

WS7-3465 ENGLISH GLAZE 8.57 3.98 25.00 100 

F-2679 50 SHEEN CAT/LACQUER 7.86 5.39 0.00 0 

CA-175 CATALYST 8.24 4.12 0.00 0 

F-2554 60 SHEEN M/R LACQUER 7.54 5.88 0.00 0 

F-2672 60 SHEEN M/R LACQUER 7.92 5.16 320.00 1,651 

LE2-3229 WHITE LACQUER 8.27 5.82 35.00 204 

07-1189 E/G SHADE 7.04 6.81 0.00 0 

08-1190 BLUE SHADE 7.10 6.61 11.00 73 

PF7-2251 WATER BASE PUTTY 11.98 0.00 6.00 0 

T-1703 GLAZE REDUCER HYSOL 10 7.27 7.27 0.00 0 

T-1743 GLAZE REDUCER HYSOL 15 7.42 7.42 0.00 0 

T-1665 50/50 CUT HYSOL 10/15 7.35 7.35 130.00 956 

T-1769 MINERAL SPIRITS 6.42 6.42 0.00 0 

T-1648 LACQUER THINNER 6.63 6.63 105.00 696 

T-1647 WASHOFF THINNER 6.61 6.61 0 

T-1529 LACQUER RETARDER 7.91 7.91 15.00 119 

T-1605 NGR STAIN REDUCER 6.63 6.63 0 
 LIST OF FIGURES (continued) 

Number Page

 C-5

T-1622 VM&P NAPTHA 6.23 6.23 55.00 343 

UV-505 STRIPCOAT 7.81 5.69 0 

 1,330 7,867 
 LIST OF FIGURES (continued) 

Number Page

 C-6

ADDITIONAL QUESTIONS ON DIRECT DETERMINATION

Do the following examples constitute direct determination? 

1.The facility used the RACT level (6.0 lbs VOC) to calculate 

emissions. 

No, an assumed content cannot qualify as a direct determination.

2.The facility used the RACT level to estimate one coating line. 

Four lines could be directly determined, but the single line 

could not be treated as a direct determination.

3. The facility reported an annual mass balance, but daily 

records were not available during the inspection. 

The record unavailability would fail the reporting requirements 

for direct determination.

4.The facility collected waste coating and shipped it offsite as 

hazardous waste. 

Yes, direct determination could be claimed if the manifests are 

on file and the solvent portion is quantified. Yes, if this 

waste is not quantified, but no "credit" is given for the 

waste. No, if this waste is not documented but is subtracted 

from the emissions.

5.For the inventory year, this source was not permitted under the 

regulation. 

This fact has no bearing on direct determination, only the 

application of Rule Effectiveness. 

6.The facility vents spray booth emissions to an incinerator and 

reports a 96 percent control efficiency and test report (the 

same mass balance documentation is submitted for uncontrolled 

emissions). 

With a control device, this calculation is no longer a direct 

determination and Rule Effectiveness must be applied.

7.The facility reports that 2 lbs VOC are consumed per 100 

pieces, and submits monthly reports of production (pieces). 
 LIST OF FIGURES (continued) 

Number Page

 C-7

Rate per unit of production is not suitable for direct 

determination where the production is not coating or solvent 

used.
 LIST OF FIGURES (continued) 

Number Page

 C-8

 APPENDIX D 

 DETERMINING SAMPLE SIZE
 LIST OF FIGURES (continued) 

Number Page

 D-9

DETERMINATION OF SAMPLE SIZE

 The sample chosen for the RE questionnaire survey should be 

representative of the relevant category population as a whole. 

This means that the size of the sample must be statistically 

adequate to represent that category population. A population 

mean or proportion is estimated by the corresponding mean or 

proportion of the sample. In addition to the size of the sample 

(i.e., the sources for which a questionnaire is completed), it is 

also necessary to consider the makeup of the sample chosen. 

 For many applications, the population parameters (i.e.,

population mean μ and population standard deviation σ) are 

usually known or can be estimated. In the case of RE, estimating 

these parameters is the objective of the survey. The population 

mean can be approximated by the sample mean with some degree of 

error. In deciding on size of sample for a given survey, several 

elements must be considered: 

•The standard deviation of the population from which the sample 

is to be drawn. Lacking this information, it can be 

estimated either from past surveys (if available) from the 

same population, from an initial survey conducted for this 

purpose (the first ten sources chosen at random) or from 

rational considerations of what this population might look 

like. 

•The degree of accuracy "e" one would like to have in the sample 

data. This is usually defined as an interval and is referred 

to as the limit of error. The sample mean will usually not 

be exactly equal to the population mean. The size of this 

difference is the limit of error "e." 

•The degree of confidence α one would like to have to be 

confident that the population mean is within the limit of 

error set above. 

 Thus, if the sample mean is used as an estimate of the 

population mean μ, we can be (1 - α) x 100 percent confident that 

the limit of error will be less than a specified amount "e" when 

the sample size is at least 

wheren =sample size 

σ =standard deviation of the population 

Install Equation Editor and doubleclick here to view equation.
 LIST OF FIGURES (continued) 

Number Page

 D-10

 e =limit of error (usually in the range of 5 to 10 percent 

of the value of the mean) 

α =confidence level 

 Zα/2 =index derived from the normal curve corresponding 

to the desired confidence levels: 

α (Percent) Zα/2 

 

 90 1.65 

 95 1.96 

 99 2.58 

 99.7 3.00 

 The following tables were developed using the equation 

presented above. They show the sensitivity of sample size with 

respect to the confidence level α, the limit of error e, and the 

standard deviation of the population from which the sample is to 

be drawn. There is a trade-off between confidence level and 

limit of error. The largest sample size provides the highest 

confidence level and lowest limit of error. In addition, larger 

sample sizes are required when the standard deviation is larger. 

 Conversely, the smallest sample size provides the lowest 

confidence level and the highest limit of error. Smaller sample 

sizes can be used when the standard deviation is lower. 

 The following example illustrates the use of the tables 

presented above. Assume that an air pollution control agency is 

interested in estimating rule effectiveness (RE) in the can 

coating industry. However, no prior estimates on RE are 

available from previous research. Lacking such an estimate, the 

initial survey was conducted on 10 facilities. Results of the 

initial survey yielded an average RE value of 80 percent with a 

standard deviation of ± 8 percent. Assuming a 90 percent 

confidence limit and a limit of error of 5 percent, the sample 

size required is obtained from Table 1 and is equal to 7. In 

this case, the survey for this category would be complete. 

However, if the standard deviation obtained from the initial 

survey was ± 10 percent and the limit of error was 5 percent, the 

number of facilities required for sampling increases from 7 to 11 

facilities, and one more questionnaire would need to be 

completed. On the other hand, choosing a larger limit of error, 

5.5 percent instead of 5 percent, will yield a sample size of 9 

facilities instead of 11. 

CHOICE OF SAMPLE SIZE 
 LIST OF FIGURES (continued) 

Number Page

 D-11

 For statistical purposes, the variables affecting the sample 

size are the limit of error and the confidence level. However, 

decisions on actual sample size to be used must also include 

considerations such as available resources and data quality 

requirements. A decision on what sample size to choose should 

begin with an estimation of the resources necessary for execution 

and data analysis. The initial survey of ten randomly-selected 

facilities can be used for that purpose. The second step in 

deciding on the size of the sample and the type of survey to be 

conducted is to determine the resources available to the 

surveying agency including staff time available for completing 

the questionnaires. The next step is to determine a sample size 

based on the statistical formulas and estimate the resources 

required to conduct the survey. Those resources are then 

compared to the resources available to the agency for the purpose 

of conducting the survey. If the resources needed exceed the 

available resources, the agency should decide on an affordable 

sample size. This is achieved by modifying the acceptable limit 

of error or confidence level or both. 

 EPA recommends that the 90 percent confidence interval (Table 

D-1) be used; the suggested sample error is 5 percent, but should 

not exceed 10 percent. State and local agencies are permitted 

latitude to choose higher confidence intervals and lower sampling 

errors. Where these methods are used, the SIP documentation 

should state the selected error and confidence levels. 
TABLE D-1. SENSITIVITY ANALYSIS OF SAMPLE SIZE: CONFIDENCE LEVEL 

Sample 

Error 

Standard Deviation

2% 4% 6% 8% 10% 12% 14% 16% 18% 

2.5% 2 7 16 28 44 63 85 112 141 3.0% 1 5 11 19 30 44 59 77 98 3.5% 1 4 8 14 22 32 44 57 72 4.0% 1 3 6 11 17 25 33 44 55 4.5% 1 2 5 9 13 19 26 34 44 5.0% 0 2 

4

7 11 16 21 28 35 

5.5% 0 1 3 6 9 13 18 23 29 6.0% 0 1 3 5 8 11 15 19 25 6.5% 0 1 2 4 6 9 13 16 21 7.0% 0 1 2 4 6 8 11 14 18 7.5% 0 1 2 3 5 7 9 12 16 8.0% 0 1 2 3 4 6 8 11 14 8.5% 0 1 1 2 4 5 7 10 12 9.0% 0 1 1 2 3 5 7 9 11 
TABLE D-2. SENSITIVITY ANALYSIS OF SAMPLE SIZE: CONFIDENCE LEVEL 

Sample 

Error 

Standard Deviation

2% 4% 6% 8% 10% 12% 14% 16% 18% 

2.5% 2 10 22 39 61 89 120 157 199 3.0% 2 7 15 27 43 61 84 109 138 3.5% 1 5 11 20 31 45 61 80 102 4.0% 1 4 9 15 24 35 47 61 78 4.5% 1 3 7 12 19 27 37 49 61 5.0% 1 2 

6 10 15 22 30 39 50 

5.5% 1 2 5 8 13 18 25 33 41 6.0% 0 2 4 7 11 15 21 27 35 6.5% 0 1 3 6 9 13 18 23 29 7.0% 0 1 3 5 8 11 15 20 25 7.5% 0 1 2 4 7 10 13 17 22 8.0% 0 1 2 4 6 9 12 15 19 8.5% 0 1 2 3 5 8 10 14 17 9.0% 0 1 2 3 5 7 9 12 15 
TABLE D-3. SENSITIVITY ANALYSIS OF SAMPLE SIZE: CONFIDENCE LEVEL 

Sample 

Error 

Standard Deviation

2% 4% 6% 8% 10% 12% 14% 16% 18% 

2.5% 4 17 38 68 107 153 209 273 345 3.0% 3 12 27 47 74 107 145 189 240 3.5% 2 9 20 35 54 78 107 139 176 4.0% 2 7 15 27 42 60 82 107 135 4.5% 1 5 12 21 33 47 64 84 107 5.0% 1 4 10 17 27 38 52 68 86 5.5% 1 4 8 14 22 32 43 56 71 6.0% 1 3 7 12 18 27 36 47 60 6.5% 1 3 6 10 16 23 31 40 51 7.0% 1 2 5 9 14 20 27 35 44 7.5% 0 2 4 8 12 17 23 30 38 8.0% 0 2 4 7 10 15 20 27 34 8.5% 0 1 3 6 9 13 18 24 30 9.0% 0 1 3 5 8 12 16 21 27 
 LIST OF FIGURES (continued) 

Number  D-15 APPENDIX E 

DEFAULT CONTROL ASSUMPTIONS FOR CTG CATEGORIES
 LIST OF FIGURES (continued) 

Number  E-2The attached table lists the CTG categories and the approximate control efficienauthors identified for the CTG categories. Many of the efficiencies depend on wis used and the solvent content. Closer analysis of the CTG documents and referimprove the rough estimates provided here. EPA has not determined the validity this listing for the purposes of RE. 
 E-3

TABLE E-1. TYPICAL VOC REDUCTION PER FACILITY FOR CTG 

 CATEGORIES BASED ON CTG DOCUMENTS

Category Lowa

(%) 

Higha

(%) 

Single 

Value 

(%) 

Co

Point Source CategoriesGasoline Loading Terminals 87 Bulk Gasoline Plants  Alternative 1  Total Plant 22  All Transfers 27  Alternative 2  Total Plant 54  All Transfers 64  Alternative 3  Total Plant 77  All Transfers 92 Fixed Roof Petroleum Tanks 90+ Refinery Processes  VPS 100  WS 95  PUT 98 Surface Coating Solvent % an

dependent 
TABLE E-1. TYPICAL VOC REDUCTION PER FACILITY FOR CTG 

 CATEGORIES BASED ON CTG DOCUMENTS (continued)

 E-4

Category Lowa

(%) 

Higha

(%) 

Single 

Value 

(%) 

Co

 Cans 60 100  Metal Coils 70 98  Fabric and Vinyl 80 100  Paper Products 80 99  Automobiles & Light Duty Trucks  Prime Coating 80 93  Top Coating 75 92  Final Repair Coating NA  Metal Furniture 50 99  Magnetic Wire 90  Large Appliances 79 95  (continued) 
TABLE E-1. TYPICAL VOC REDUCTION PER FACILITY FOR CTG 

 CATEGORIES BASED ON CTG DOCUMENTS (continued)

 E-5

 Misc. Metal Parts  Process Modification 50 98  Exhaust Gas Treatment 90+  Flatwood Paneling 70 90 Graphic Arts  Publication Rotogravure 75  Packaging Rotogravure 65  Flexographic Printing 60 Leaks from Petroleum Refineries 62 Based on 15,External Floating Roof Tanks 33 99 Gasoline Truck Leaks & Vapor Collection 

NA 

Synthetic Pharmaceutical Manufacturing NA Rubber Tire Manufacturing  Carbon Adsorption 62 86  Incineration 59 81  Water-based Coatings 97 Leaks from NG/Gasoline Processing Plants 

 72 Model plants 

Mfg. of HDPE, PP, and PS Resins 98 Model Plants SOC & Polymer Mfg. Equipment Fugitives 36 under RACT Large Petroleum Dry Cleaners 66 72 
TABLE E-1. TYPICAL VOC REDUCTION PER FACILITY FOR CTG 

 CATEGORIES BASED ON CTG DOCUMENTS (continued)

 E-6

SOCMI Air Oxidation Processes Thermal Oxidation 98 With control

baseline 

 53  (continued) 
TABLE E-1. TYPICAL VOC REDUCTION PER FACILITY FOR CTG 

 CATEGORIES BASED ON CTG DOCUMENTS (continued)

 E-7

Area Sources

Service Stations - Stage I  Transfer Losses 95+  Total Facility 50 Cutback Asphalt 100 Solvent Metal Cleaning  Cold Cleaning 50 53 +/- 20%  Open-top Vapor Degreasing 45 60 +/- 15%  CD 25 60 +/- 10% Perchloroethylene Dry Cleaners 40 70 Carbon Adsor

1Users should select the low value from a range unless another value is j

hundred percent should never be used unless the emissions are directly dethas been an irreversible process change.