Agency Research Triangle Park, NC

1EPA Potential to Emit

A Guide for 

Small Businesses

Potential to Emit

A Guide for Small Businesses

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Research Triangle Park, North Carolina

October 1998

2Printed on paper that contains at least 20

percent postconsumer fiber.
POTENTIAL TO EMIT

Disclaimer

This report has been reviewed by the Office of Air Quality Planning

and Standards (OAQPS), U.S. Environmental Protection Agency

(EPA) and approved for publication. The statements in this

guidebook are intended solely as guidance, and this guidebook is

not a legally binding document. Contact your state air pollution

control agency or state small business assistance program to 

clarify all requirements that may apply to your business.

For more information...

To obtain more information or additional copies of this guidebook,

call your state small business assistance program or your state or

local air pollution control agency. Also, visit the EPA’s Technology

Transfer Network – Small Business Assistance Program web site at:

http://www.epa.gov/ttn/sbap to get information on your state

small business assistance program or to find this document and

additional materials concerning this subject. If you do not have

access to the Internet, you can contact EPA’s Clean Air

Technology Center (CATC) Hotline at 919-541-0800. 
WHAT IS POTENTIAL TO EMIT? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

What is the purpose of this document? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

What is potential to emit? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

What pollutants are regulated under the Clean Air Act? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Do I need to be concerned about “double-counting” these emissions as 

criteria pollutants and HAPs? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

What does it mean if my business is a “major source” of a criteria pollutant? . . . . . . . . . . . . . .4

What does it mean if my business is a “major source” of HAPs? . . . . . . . . . . . . . . . . . . . . . . . . .5

Is my business a “minor source” of air emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

What air pollution regulations apply to my business? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

How do I know whether my business is a “major” or “minor” source 

of air pollutants? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

What is “maximum capacity?” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

What types of limitations might reduce my maximum capacity? . . . . . . . . . . . . . . . . . . . . . . . .7

Can control measures qualify as limitations on my maximum capacity? . . . . . . . . . . . . . . . . . .8

How can I be sure of my maximum capacity? Do alternatives 

exist if it’s hard to figure out my capacity? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Can I qualify as a minor source of air emissions without determining 

my maximum capacity? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

If I already have a permit that limits my capacity or emissions, 

do I need to do anything else? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

HOW DO I DETERMINE POTENTIAL TO EMIT? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

How do I determine the potential to emit for my business? . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Does a screening method exist that can easily tell me if I am a major or minor 

source before I try to determine my potential to emit? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

What methods can I use to determine my emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Which method should I use to calculate emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

What information do I need to know to use one of the methods you 

described to determine my business’s potential to emit? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

What are fugitive emissions, and do they need to be considered 

when calculating my potential to emit? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

How does the number of hours my business operates affect my 

emissions estimates? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

If after calculating my potential to emit my business is above 

major source levels, what do I do? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

TABLE OF CONTENTS
EXAMPLES OF POTENTIAL TO EMIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Could you give some examples of how potential to emit is determined? . . . . . . . . . . . . . . . . . .17

Example 1: Potential to Emit of a Small Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

How does my fuel type determine emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

How can I determine my boiler’s rated capacity? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

How can I determine the heating value of my fuel? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Can I use EPA’s screening method to determine if I am a major or minor source? . . . . . . . . . . .18

What method should I use to figure out my emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Where can I find emission factors? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

How do I figure out the potential to emit for my small boiler using 

an emission factor? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Am I a major or minor source of emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Example 2: Potential to Emit of a Sheetfed Offset Lithographic Printing Operation . . . . . . . . .21

What is my maximum capacity? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

What pollutants do I emit? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Can I use EPA’s screening method to determine if I am a major or minor source? . . . . . . . . . . .22

What method should I use to estimate my air emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Do I need to add in fugitive emissions or equipment leaks? . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

What is my potential to emit VOC emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

What is my total potential to emit for VOCs? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

What is my potential to emit HAPs emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

What is my total potential to emit HAPs? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Am I a major source of either VOC or HAP emissions? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

WHERE CAN I GET MORE INFORMATION? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

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

APPENDIX B: LIST OF HAZARDOUS AIR POLLUTANTS (HAPs) . . . . . . . . . . . . . . . . . . . . . . . . . .B-1

APPENDIX C: REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C-1

TABLE OF CONTENTS
1

What is the purpose of 

this document?

What is potential to emit?

As a small business, you may have to meet certain

requirements in the Clean Air Act to limit the amount of 

pollutants that are released into the air. One way to find out

which requirements apply to you is to figure out your 

business’s potential to emit. This document answers the 

following questions:

• What is potential to emit?

• How do I figure out the potential to emit for my business?

You may wish to contact your state air pollution 

control agency or state small business assistance program 

with questions you have as you read this document 

(for who to contact, see “Where can I get more information?” 

on page 28). Also see Appendix C for suggested sources 

of information. 

Potential to emit refers to the highest amounts of certain

pollutants that your business could release into the air (even if

you have never actually emitted the highest amount). Potential to

emit considers the design of your equipment. It can also consider

certain controls and limitations on the operation of your business,

as discussed throughout this document.

WHAT IS POTENTIAL TO EMIT?
2

What pollutants are 

regulated under the Clean 

Air Act?

It is important to know whether your business is a “major”

or “minor” source of air emissions (how to do this is discussed

throughout this document). Many requirements of the Clean Air

Act only apply to major sources. If your business is not a major

source, then you are considered a minor source. As a minor source,

you may not have to meet certain requirements, or may have

requirements that are easier to meet. Once a business is classified

as a major source, generally its classification cannot be changed to

a minor source except under certain limited circumstances that

involve additional administrative and permitting procedures.

Clean Air Act requirements for major sources make 

sure that:

• Air quality is not made worse. 

• Air emissions are controlled.

• Businesses that are major sources have operating permits.

To find out whether your business is a major or minor source of

emissions, you need to figure out its potential to emit certain air

pollutants. Then compare these amounts to the amounts that the

government considers to be “major” releases of air emissions.

This document will describe how to figure out your emissions.

But first we discuss what pollutants you need to be concerned

about and what amounts of emissions the government considers

to be “major.”

Pollutants are regulated under the Clean Air Act based 

on whether they can have negative effects on people’s health or

the environment. Pollutants that are regulated fall into two 

main categories:

• Criteria pollutants

• Hazardous air pollutants (HAPs)

WHAT IS POTENTIAL TO EMIT?
3

Appendix A provides definitions of criteria pollutants,

HAPs, and other terms that are commonly used when discussing 

air pollutants. Table 1 lists the six criteria pollutants covered by

the Clean Air Act. For ozone, one of the criteria pollutants, “

precursors” are regulated rather than ozone itself. Precursors are

substances that react together to form a pollutant. The precursors

of ozone are volatile organic compounds (VOCs) and nitrogen

oxides (NOx).

Table 1. Criteria Pollutants and Precursorsa

a A precursor of a criteria pollutant is a compound that reacts in the air to produce that pollutant.

b Several categories of particulate matter may be regulated in different states. Contact your

state air pollution control agency or state small business assistance program to find out

which categories are covered by your state (for who to contact, see “Where can I get 

more information?”).

The Clean Air Act also regulates 188 hazardous air 

pollutants (HAPs), also known as air toxics. Appendix B provides a

complete list of HAPs. Some HAPs are volatile organic compounds

(VOCs) and count as criteria pollutants as well as HAPs emissions.

HAPs in particle form can also be counted as particulate matter

(PM), another criteria pollutant. 

WHAT IS POTENTIAL TO EMIT?

Ground-level ozone (“smog”)

Precursors: Volatile organic compounds (VOCs)

Nitrogen oxides (NOx)

Carbon monoxide (CO)

Particulate matter (PM)b

Nitrogen oxides (NOx)

Sulfur dioxide (SO2)

Lead (Pb)
4

What does it mean if my 

business is a major source

of a criteria pollutant?

When determining your potential to emit, some HAPs

need to be reported as both HAPs and as VOCs or PM. Usually

“double-counting” is only a concern if the emission results will

be used to determine emission fees. To be sure, contact your

state air pollution control agency or state small business 

assistance program (for who to contact, see “Where can I get

more information?”).

Contact your state air pollution control agency or state

small business assistance program to find out the emission levels

in your area which classify a business as a major source of criteria

pollutants (also see Table 6 in Appendix A) (for who to contact,

see “Where can I get more information?”). If your business 

qualifies as a major source of criteria pollutant emissions, you

must do two things:

• Get a Title V operating permit.

• Meet emission limits established by your state.

Title V Permit. Your Title V permit will describe all of

your federal obligations for controlling air pollution (additional

state and local requirements may exist). Examples of common

requirements that may be listed in your permit include:

• Limits on emissions.

• Maintaining progress reports, records, and a compliance schedule. 

• Notifying your state air pollution control agency (or possibly

EPA) of any violations of your permit conditions.

• Monitoring your compliance with emission limits/requirements.

Your specific obligations may vary, so contact your state

air pollution control agency or state small business assistance 

program to find out how to obtain a permit and about particular

permit requirements (for who to contact, see “Where can I get

more information?”).

WHAT IS POTENTIAL TO EMIT?

Do I need to be concerned 

about double-counting

these emissions as criteria 

pollutants and HAPs?
5

What does it mean 

if my business is a 

major source of HAPs? 

State emission limits. Your state sets emission limits for

criteria pollutants in part based on the location (or area) of your

business. Location is important because “nonattainment” areas

have stricter emission requirements than “attainment” areas.

Attainment areas are those areas that meet National Ambient 

Air Quality Standards (called NAAQS). There is a NAAQS for

each criteria pollutant. Nonattainment areas do not meet

NAAQS. Also, your business may be located in an attainment

area for federal air quality standards, but in a nonattainment 

area for state/local standards. To find out whether your business

is located in an attainment or nonattainment area, contact 

your state air pollution control agency or state small business

assistance program (for who to contact, see “Where can I get 

more information?”). 

Your business is a major source of HAPs if it has the

potential to emit either one of the following:

• At least 10 tons per year of any one of the 188 HAPs (listed in

Appendix B).

• At least 25 tons per year of total HAPs.

If your business qualifies as a major source of HAPs, then

you must meet certain emission performance standards. To meet

these standards, you must do two things:

• Meet certain air pollution control limits (which are established

by the federal government based on performance standards that

have been achieved in practice by a particular type of process or

machinery).

• Get a Title V operating permit (which will list your air pollution

control requirements).

For certain industries, the federal government may not yet

have set performance standards. If this is true for your business,

then you may only have to get a Title V operating permit for now

to meet federal requirements. Or, state air pollution control agencies

may determine performance standards on a case-by-case basis for

some types of industries. In addition, a business that is a major

source of HAPs may also have to meet state or local requirements.

Contact your state air pollution control agency or state small

business assistance program to find out your requirements (for

who to contact, see “Where can I get more information?”).

WHAT IS POTENTIAL TO EMIT?
6

Is my business a minor 

source of air emissions?

Businesses that cannot emit as much criteria pollutants 

or HAPs as a major source are called minor sources. Your business

can qualify as a minor source of air emissions if it meets one of

the following:

• Your potential to emit criteria pollutants or HAPs is below

major source levels.

• Your potential to emit is at or above major source levels, but

you limit your operations or emissions in certain ways. Generally,

if your business qualifies as this type of minor source, you will

need to get a permit through your state air pollution control

agency.1 The limits on your operations or emissions that might

qualify you as a minor source include:

• You follow specific requirements to use, operate, and

maintain air pollution control devices.

• You follow specific requirements to restrict operations 

to a certain amount of time.

• You use specified restrictions on the types and 

amounts of input materials used (for example, 

fuel usage or solvent usage).

If your business has any of the limits discussed above that

qualifies it as a minor source, you will probably be required to

keep records or other information to show that your business is

operating within its limit.

The regulations that apply to your business depend on 

the types and amounts of criteria pollutants (see Table 1) and 

hazardous air pollutants (HAPs, see Appendix B) that you emit or

have the potential to emit. Whether your business is a major or

minor source of air emissions, contact your state air pollution

control agency or state small business assistance program to find

out what regulations apply (for who to contact, see “Where can 

I get more information?”). 

WHAT IS POTENTIAL TO EMIT?

What air pollution 

regulations apply to 

my business?

1 In some states, certain businesses that have very low actual emissions may not need to go

through the permitting process; instead, they may be able to become a minor source by

meeting industry-specific requirements in federal, state, or local regulations.
7

How do I know whether 

my business is a major

or minor source of 

air pollutants?

What is "maximum 

capacity?"

You need to consider two factors to determine whether

your business is a major or minor source of air emissions:

• Your business’s “maximum capacity.” 

• Air pollution regulations and policies that apply to your business,

particularly those that affect your potential to emit by limiting

your maximum capacity.

Both of these factors are discussed below.

Your business’s maximum capacity is based on the 

amount of input materials used and products produced by each

piece of equipment you have. Begin by assuming that your business

operates continuously throughout the year (which equals 8,760

hours). Generally you must assume the highest amounts of 

inputs and products possible, which result in the highest level 

of air emissions. 

However, when certain limitations (that can be confirmed

by regulators) are present at your business, you may instead

base your maximum capacity on the amount of input materials

that can be used and the products that can be produced given

these limitations.

The limitations present at your business must be 

unchanging and unavoidable physical constraints in order to

reduce your maximum capacity. These constraints must result in

predictable upper limits on your operations and capacity. (Note

that changeable market conditions or business plans do not 

qualify to limit your operations and capacity.)

WHAT IS POTENTIAL TO EMIT?

What types of limitations 

might reduce my 

maximum capacity?
8

A common type of limitation that could reduce your 

maximum capacity might involve setting limits on operating rates

or operating times of equipment. For example, in a paint-spraying

booth at a small autobody shop, there is a limitation on the number

of cars that can be painted and dried in a given amount of time

because of the time it takes to perform each task required (e.g.,

preparation of the surface, painting, drying, etc.). In figuring out

the maximum capacity of such a business, the owner does not

have to assume that the paint-spraying equipment operates every

hour throughout the year. Instead, he or she can assume that it

operates only as much as is necessary to paint the maximum

number of cars that the booth can handle if operated every hour

throughout the year.

Another example is limitations in the operation of country 

grain elevators. These businesses serve a limited and generally

unchanging geographic area that can produce only a finite amount

of grain. While the amount of grain harvested might fluctuate,

local grain production generally will not exceed a certain upper

limit. It is this upper limit that forms the basis for determining a

grain elevator’s maximum capacity.

Similarly, the operation of emergency generators is limited

to a certain number of hours — the number of hours for which

the emergency generator must substitute for regular power. An

upper limit of the number of hours the generator will operate can

be estimated quite accurately. The upper limit of hours of operation

will be much less than the 8,760 hours per year that is normally

assumed to determine maximum capacity.

Control measures can qualify as limitations that reduce

your maximum capacity only if they are operated and maintained

continuously for reasons other than air quality protection.

Examples of using controls for purposes other than for air quality

include: quality control, product recovery, or operating efficiency.

For example, at a dry cleaning facility, a closed loop dry cleaning

machine may be used for operating efficiency. As a side effect,

emissions of HAPs and VOCs may also be reduced.

WHAT IS POTENTIAL TO EMIT?

Can control measures 

qualify as limitations on 

my maximum capacity?
9

How can I be sure of 

my maximum capacity? 

Do alternatives exist if 

its hard to figure out 

my capacity? 

Check with your state air pollution control agency or 

state small business assistance program if you are unsure of your

maximum capacity (for who to contact, see “Where can I get

more information?”). Agencies realize that uncertainties exist in

determining capacity, particularly for certain types of processes,

that may make it difficult to figure out what a business’s maximum

capacity is. And yes, there are alternatives to figuring out your

own maximum capacity. In some cases, it may be easier for a

business to accept a limit set by the state (called an “enforceable

limit”), such as one that already exists in a permit, rather than

trying to figure out your maximum capacity. 

You can also get guidance documents and policy memoranda

that discuss limitations (known as “inherent limitations”) on

maximum capacity from your state air pollution control agency

or state small business assistance program. These materials 

offer further assistance on maximum capacity. Appendix C

(“References”) includes some of these materials. Also check out

this information on the Internet at: http://www.epa.gov/ttn/oarpg

A business can qualify as a minor source through certain

permit and other options without determining maximum capacity.

Check with your state air pollution control agency or state small

business assistance program for information on these options,

which include:

• Case-by-case permits for construction and/or operation.

• General permits for a specific type of business.

• Meeting certain conditions (known as “prohibitory rule”); 

this option does not require applying for a permit).

WHAT IS POTENTIAL TO EMIT?

Can I qualify as a minor 

source of air emissions 

without determining my 

maximum capacity?
10

The last option listed above applies to certain types of

businesses that are known to have low emissions. Some states

have programs that make it easy to get prohibitory rule limits,

such as mailing in a postcard in which the business owner agrees

to meet certain limits. EPA expects that prohibitory rule limits

will be used increasingly in the future and has developed guidance

on this option (see the references in Appendix C: “Potential to

Emit Guidance for Specific Source Categories” and “Technical

Support Document for Potential to Emit Memo.”)

Other options also exist. Permits or other conditions can

be applied that reduce your potential to emit based on one or

more of the following:

• The use of emission control devices.

• Restrictions on the rate or time of operations.

• Limitations on the amounts or types of raw materials used.

Businesses using such options are generally required to

keep adequate compliance records and to report regularly to state

air pollution control agencies.

In addition, some states have chosen to follow a temporary

EPA “transition policy” (until December 31, 1999). This policy

allows a business to be treated as a minor source if the business

maintains records showing that its actual emissions are less than

50 percent of major source levels. Also, if a business has actual

emissions between 50 and 100 percent of major source levels, 

it may qualify as a minor source by meeting state limits on its

potential to emit (e.g., through a permitting program). Not all states

use this optional policy, so check with your state air pollution

control agency or state small business assistance program to find

out whether your state offers this option (for who to contact,

see “Where can I get more information?”). After this temporary

transition policy ends, most businesses with low emissions

should be able to qualify as a minor source through any of the

methods discussed above.

WHAT IS POTENTIAL TO EMIT?
11

If your business meets the following criteria, there’s a good

chance that you are complying with limits for the potential to emit:

• Your emission controls are permanent.

• Your business is legally obligated to obey conditions for potential

to emit limits.

• Your potential to emit limits do not relax state requirements

already accepted by EPA.

• Your limitations on potential to emit are technically accurate

and quantifiable.

• Your records of emissions allow for monthly compliance checks

by government agencies.

• Your recordkeeping, reporting, and monitoring are sufficient to

demonstrate compliance.

Not all permit limits meet these requirements. Also, a

single permit limit does not guarantee that you are a minor

source for all pollutants. You must still be a minor source for

all pollutants to qualify as a minor source. To do this, you must

determine your potential to emit for each pollutant, including

HAPs. Check with your state air pollution control agency or

state small business assistance program to find out more about

different types of limits (for who to contact, see ”Where can I

get more information?”).

WHAT IS POTENTIAL TO EMIT?

If I already have a permit 

that limits my capacity or 

emissions, do I need to 

do anything else?
12

Your maximum capacity determines your potential to

emit. So, once you’ve identified your maximum capacity (or have

chosen alternatives, such as permit limits or other state limits),

as described above, you can determine your potential to emit. 

The steps involved in determining your emissions are presented

in Box 1. Specific methods for figuring out your potential to emit

are described below.

Box 1. Basic Steps for Determining Emissions

Yes. EPA has developed guidance that you can use to

quickly determine if you are a major or minor source (see EPA,

1998a in the Reference section [Appendix C]. The screening

method covers pollutants and materials that are of the greatest

concern for different types of businesses. The method includes

cutoff levels for materials that you may use (e.g., solvents, etc.). 

If you use less than the cutoff level for a certain material, then

you are probably a minor source. In all cases, you should confirm

your results with your state air pollution control agency. If the

screening method does not apply to you, then you can use the

procedures described below to determine your potential to emit.

HOW DO I DETERMINE POTENTIAL TO EMIT?

1. Identify all sources of emissions.

2. Identify all criteria pollutants and hazardous air pollutants (HAPs)

that your business emits. (Note that other types of pollutants may

also be regulated and require a Title V permit; check with your state

air pollution control agency or state small business assistance

program for a list of all regulated air pollutants. For who to contact,

see “Where can I get more information?”).

3. Select a method to use from Table 2 below to determine 

your emissions.

4. For each criteria and hazardous air pollutant, determine the

maximum amount that each production process or piece of

equipment in your business can emit in one year.

5. For each criteria and hazardous air pollutant, add the maximum

emissions from all production processes/equipment.

Does a screening method 

exist that can easily tell 

me if I am a major or 

minor source before 

I try to determine my 

potential to emit?

How do I determine the 

potential to emit for 

my business?
13

What methods can I use 

to determine my emissions?

HOW DO I DETERMINE POTENTIAL TO EMIT?

You can use one of the following four methods to 

determine your emissions:

• Use test data (onsite measurements).

• Use a material-balance approach (comparing inputs and outputs).

• Use source-specific models (based on information about your

business’s operations).

• Use emission factors (based on industry-average emission rates).

Table 2 describes these methods in more detail.

Table 2. Emissions Calculation Methods

It depends on the type of business and types of emissions

you have, what information and resources are available, and the

degree of accuracy required. Consult your state air pollution control

agency or your state small business assistance program before

choosing a particular method (for who to contact, see “Where can I

get more information?”). Different methods may be used for 

different types of emissions. Whichever method you use, when

you determine your potential to emit, assume that no pollution

controls are in place. Each of the methods is discussed below to

help you decide which method best suits your business.

Method Description

Test data Onsite measurement of emissions.

Material-balance calculations Estimate emissions by comparing types and quantities of inputs to types and

quantities of outputs.

Source-specific models Formulas for emissions using source-specific parameters such as types and

quantities of inputs, operating hours, and physical characteristics of equipment.

Emission factors Uses average pollutant emission rates (provided by EPA, other agencies, or

equipment vendors), multiplied by time or frequency of operation, to obtain

emissions. Emission factors specific to your business can be used but should 

be approved by the state air pollution control agency.

Which method should I use 

to calculate emissions?
14

1.Test data method. This method can provide the most accurate

estimates of emissions. Unfortunately the data needed are often

expensive to obtain, particularly for businesses that emit a 

variety of pollutants or have a lot of “fugitive emissions.”

(Fugitive emissions are those resulting from leaks or nonlocalized

escape, such as from spraying operations. Fugitive emissions 

are discussed in more detail later in this document—see the

question: “What are fugitive emissions...?”.) Useful test data 

are easier to obtain when emissions come primarily from a

point source, such as a smokestack. It may be necessary to 

collect test data over a period of time and from multiple 

production areas to gain a reliable measure of average emissions.

Only experienced stack testers should measure emission samples

and estimate total emissions. 

2.Material-balance approach. This method is appropriate for 

businesses that lose a high percentage of input material to the

atmosphere (such as solvents in degreasing, cleaning, and coating

processes). A material-balance approach can be problematic 

for operations in which: inputs are consumed; inputs are 

chemically combined; or losses to the atmosphere make up

only a small part of the total throughput. The material-balance

approach requires accurate records of the amounts of material

used and the waste generated; such records often can be 

difficult to maintain.

3. Source-specific models. These models are available for only 

a relatively small number of industrial operations. If you want

to use this method, you must make sure that the formulas

used are relevant to your particular business. You also must

determine correct values for parameters that are plugged 

into the equations. 

4.Emission Factor method. This method uses EPA emission 

factors that represent industry averages. An emission factor

shows the relationship between an air emission and a measure

of production (e.g., pounds of SO2 per 1,000 gallons of input).

Equipment-specific emission factors can often be obtained from

equipment vendors, especially through emission performance

guarantees or from actual test data of similar equipment. It is

important to use factors that are relevant for a particular 

production process. Emission factors should account for periods

of disrupted operation as well as routine operation. While this

method has some limitations (e.g., it is simplistic and lacks

specific data), it is often the best or only practical means for

estimating emissions.

HOW DO I DETERMINE POTENTIAL TO EMIT?
15

EPA has developed emission factor ratings ranging from

best-to-worst (A through E) which can be found in EPA’s AP-42

document (see reference in Appendix C). These ratings indicate

the appropriateness of using the EPA factors to estimate average

emissions in a particular industry. Specific emission factors based

on your business can be used instead of EPA emission factors, but

should be approved by the state air pollution control agency. It

should be noted that emission factors are not EPA-recommended

emission limits or standards.

You can obtain further information on methods for

determining potential to emit from state air pollution control

agencies, state small business assistance programs, EPA, trade

associations, and vendors. It is important to remember that you,

the business owner or operator, are ultimately responsible for

using the best data available. Your data should be accurate and

representative of your emissions. If you had reasonable access to

better sources of data but did not use the information because 

you received poor advice, you remain responsible for not using the

best available data. 

The information you need to determine your potential to

emit depends on the method you selected. The emission-factor

method, which is the simplest of the four methods described

above, generally requires only the appropriate emission factors

and the maximum operation rates of your business processes. 

For source-specific models, you need to know a greater variety of

information, such as the chemical composition of the inputs, the

temperatures at which processes occur, and the dimensions of 

the equipment used. Material-balance and test data methods

require a number of specific measurements made at the business

establishment itself.

You must estimate emissions for all pollutants emitted 

by your business, whether criteria air pollutants or hazardous air

pollutants (HAPs). (See Table 1 for a list of criteria pollutants 

and Appendix B for a list of the 188 EPA-regulated HAPs.) Your

estimates must be based on the collective total of emissions 

from a particular business (e.g., if a business has five printing

lines, potential to emit must be based on the total emissions 

from all five lines). 

HOW DO I DETERMINE POTENTIAL TO EMIT?

What information do I 

need to know to use 

one of the methods you 

described to determine my 

businesss potential 

to emit?
16

Fugitive emissions refer to air pollutant emissions that

enter the atmosphere from a business without first passing

through a stack or duct designed to direct or control their flow.

While air emissions often do pass through a stack or duct (or are

otherwise captured) before being discharged to the atmosphere,

some fugitive emissions typically escape the system without

being captured. 

Depending on the purpose of your potential to emit 

calculation, you may or may not be required to include fugitive

emissions. Also, some regulations require certain types of businesses to include fugitive emissions when determining their

potential to emit. Contact your state air pollution control agency

or state small business assistance program for guidance on

whether to include fugitive emissions in your potential to emit

(for who to contact, see “Where can I get more information?”). 

As discussed earlier, in determining potential to emit 

you should assume that equipment operates every hour of the

year (8,760 hours per year), unless certain limitations affect how

much your business can operate (see the earlier question, “What

is maximum capacity?” which describes these limitations). 

If such limitations are present, you should assume that your

equipment operates for the maximum number of hours allowed

by the limitations. In the case of batch operations, when emissions

are not continuous in time, determine your potential to emit by

multiplying the emissions per batch by the maximum number of

batches per year. 

If your potential to emit is just above major source levels,

carefully check and document any assumptions used in your 

calculation. If your numbers are correct, you might still qualify as a

minor source if you limit your operations in certain ways (see the

earlier question, “Is my business a minor source of air emissions?”) 

HOW DO I DETERMINE POTENTIAL TO EMIT?

What are fugitive emissions,

and do they need to be 

considered when calculating 

my potential to emit?

How does the number 

of hours my business 

operates affect my 

emission estimates?

If after calculating my 

potential to emit my 

business is above major 

source levels, what do I do?
17

EXAMPLES OF POTENTIAL TO EMIT

Could you give some 

examples of how potential 

to emit is determined?

How does my fuel type 

determine emissions?

Example 1: 

Potential to Emit of 

a Small Boiler

Below are two examples of how to determine potential

to emit. The first is for a small boiler, the second is for a 

lithographic print shop. The small boiler example uses 

emission factors. The print shop example uses the materialbalance approach.

A small business operates a boiler for process heating. 

The boiler fires exclusively natural gas. According to the state air

pollution control agency, the major source level for all criteria

pollutants for the area in which this business is located is 100

tons per year. Emissions are determined based on:

• The type of fuel burned

• The rated capacity of the boiler (this is your maximum capacity)

• The heating value of the fuel

• Maximum potential hours of operation per year

• Emission factors for pollutants

The boiler typically operates at or close to its maximum 

of 8,760 hours/year. The rest of the items listed above are 

discussed below.

Different fuels result in different types and amounts of 

pollutants due to the specific composition of the fuel. 

Most manufacturers place a metal plate on the boiler that

identifies the boiler’s rated capacity. The rated capacity should

also be contained in the manufacturer’s literature or operations

manual. The rated capacity should be in units of “million British

thermal unit per hour” (MMBtu/hr). For this example, the rated

capacity of the boiler was listed on the boiler as 15 MMBtu/hr.

How can I determine my 

boiler’s rated capacity?
18

EXAMPLE 1: SMALL BOILER

How can I determine the 

heating value of my fuel?

Can I use EPA’s screening 

method to determine 

if I am a major or 

minor source?

What method should I use 

to figure out my emissions?

Your fuel supplier can provide you with this information.

If you are unable to contact the supplier, you can instead use

average values from Appendix A of EPA’s AP-42 document (which

is listed in the References section). For this example, the heating

value of the natural gas is 1,050 MMBtu per MMcf (which stands

for million British thermal units per million cubic feet of gas),

based on information from the fuel supplier.

Yes. According to EPA’s screening method (see EPA, 

1998a in the References in Appendix C), if you burn no more than

710 million cubic feet per year, you are probably a minor source

for all pollutants. Since in this example your boiler capacity is 

15 MMBtu/hr, at a heating value of 1,050 MMBtu/MMcf, your 

maximum fuel burning rate is 0.014 MMcf/hr (15 MMBtu/hr

divided by 1,050 MMBtu/MMcf = 0.014 MMcf/hr). At 8,760 hours

per year, your maximum annual fuel burned is 123 MMcf/yr

(0.014 MMcf/hr x 8,760 hr/yr = 123 MMcf/yr). Since 123 MMcf/yr

is below the 710 MMcf/yr cutoff, you are probably a minor source.

You should confirm this information with your state air pollution

control agency. If the screening method is not sufficient to determine whether you are a major or minor source, you can use the

procedures described below to determine your potential to emit.

Emission factors are appropriate to use for this example

because they are the only practicable and economically feasible

method for this business. 

EPA’s AP-42 document (listed in the References in

Appendix C) contains emission factors for boilers firing natural

gas (see Section 1.4 and Tables 1.4-1, 1.4-2, and 1.4-3 of AP-42).

Also check with your state air pollution control agency or small

business assistance program because some agencies have additional

emission factors that should be used (for who to contact, see

“Where can I get more information?”). Table 3 lists emission factors

for small boilers from EPA’s AP-42 document. 

Where can I find 

emission factors?
19

EXAMPLE 1: SMALL BOILER

How do I figure out the 

potential to emit for my 

small boiler using an 

emission factor?

Table 3. Pollutant Emission Factors for a Small Boilera

a Emission factors obtained from EPA’s AP-42, Tables 1.4-1, 1.4-2, and 1.4-3 (see Reference

list in Appendix C) 

For each pollutant, you need to:

• Determine the “hourly heat input”: divide the boiler’s 

rated capacity by the heating value of the fuel to get the 

hourly heat input.

• Then multiply the hourly heat input by the emission factor 

for the pollutant of concern to get the emission rate.

• Multiply the emission rate by the maximum hours of 

operation per year. The result will be the pounds of the 

pollutant emitted each year. 

• Finally, you need to change the annual emissions from pounds to

tons; you do this by dividing your annual emissions in pounds

by 2,000 (because there are 2,000 pounds in 1 ton). 

Box 2 summarizes the procedure for figuring out the 

potential to emit for the boiler in this example:

Box 2. Potential to Emit for a Criteria Pollutant

Pollutant Emission Factor

SO2 0.6 lb/MMcf

NOx 140 lb/MMcf

CO 35 lb/MMcf

VOC 5.8 lb/MMcf

PM 13.7 lb/MMcf

Potential to Emit for a Criteria Pollutant (in tons/year) 5

Step 1: Rated capacity of the boiler (in MMBtu) 4 Heating value of the fuel (in MMBtu/MMcf) 5 hourly heat input (in MMcf per hr)

Step 2: 3 Emission factor (in lb per MMcf) 5 emission rate (in lb per hr)

Step 3: 3 Maximum hours of operation (in hours per year) 5 annual potential to emit (in lb of emissions per year)

Step 4: Now, change from lb to tons by dividing by 2,000: 4 2000 lb 5 tons of pollutant per year 
20

EXAMPLE 1: SMALL BOILER

Potential to emit for the other pollutants is calculated in

the same way; Table 4 displays the results:

Table 4. Potential to Emit for Small Boiler

The values determined above for the potential to emit

show that this boiler is a minor source because its emissions of

criteria pollutants lie below major source levels for criteria 

pollutants in this area (the major source levels were obtained

from the state air pollution control agency), and this business

does not emit HAPs.

Pollutant Potential to Emit

SO2 0.038 tons/year

NOx 8.6 tons/year

CO 2.2 tons/year

VOCs 0.34 tons/year

PM 0.86 tons/year

Am I a major or minor 

source of emissions?

Potential to Emit NOx 5

Step 1: 15 MMBtu per hour 4 1,050 MMBtu per MMcf 5 0.014 MMcf/hr

(rated capacity) (heating value of fuel) (hourly heat input)

Step 2: 3 140 lb NOx per MMcf 5 1.96 lb NOx per hr 

(emission factor) (emission rate)

Step 3: 3 8,760 hours per year 5 17,170 lb NOx per year 

(maximum hours of operation) (annual potential to emit, in lb per year)

Step 4: 4 2,000 lb 5 8.6 tons of NOx per year 

Box 3. The potential to emit NOx is determined as: 
21

EXAMPLE 2: PRINTING OPERATION

A small printing company operates several sheetfed offset

lithographic presses. Instead of figuring out its maximum capacity,

the company has accepted an operating limit from the state of

16,000 pounds of ink per year, and 1,350 gallons of total solvent

per year with an average VOC content of 6.6 pounds per gallon.

These limits are based on the company’s best estimate of the

maximum amounts of inks and solvents that will be used. (If the

business owner were to determine maximum capacity instead of

accepting a predetermined limit from the state, he or she would

need to determine the maximum operating schedule, line speed,

and drying time, which might be difficult to figure out.)

• For ink: 16,000 pounds of ink per year, which is the operating

limit you accepted from the state.

• For solvents: 1,350 gallons of total solvents per year with an

average VOC content of 6.6 pounds per gallon, which you also

accepted as a limit from the state.

The ink, cleaning solvent, blanket wash solvent, and 

fountain solution you use all contribute to VOC and HAP 

emissions. You can get some of the information you need from

your state air pollution control agency, state small business 

assistance program, and Material Safety Data Sheets (MSDS)

located at your business, including: 

• Find out from your state air pollution control agency or state

small business assistance program what the major source level

for VOCs is. (For this example, according to the state agency,

the major source level for VOCs is 50 tons per year.)

• Comparing your MSDS with the list of HAPs in Appendix B of

this document tells you that you emit the following HAPs from

your inks and solvents:

toluene

ethylene glycol

• Look at your MSDS to determine the specific VOC and HAP

content of the inks and solvents you use.

Table 5 lists the relevant input materials, their maximum

usage rates, and their VOC and HAP content based on the MSDS. 

Example 2: 

Potential to Emit of a 

Sheetfed Offset 

Lithographic Printing 

Operation

What is my 

maximum capacity?

What pollutants do I emit?
22

EXAMPLE 2: PRINTING OPERATION

Yes. According to EPA’s screening method (see EPA, 

1998a in Appendix C), if your printing business:

• Uses less than 7,125 gallons of cleaning solvent and fountain

solution per year, you are probably a minor source for VOCs.

• Uses less than 3,333 gallons of all materials that contain 

hazardous air pollutants and less than 1,333 gallons of material

containing any one HAP, you are probably a minor source 

for HAPs. 

Since, in this example, you have accepted a limit of 1,350

gallons of total solvent per year, you are probably a minor source

for VOCs and total HAPs. Based on the solvent data in Table 5,

the maximum solvent usage for any one HAP is the 500 gallons

per year blanket wash solvent, which contains toluene. Because

this is less than 1,333 gallons, you are probably also a minor source

for any individual HAP. You should confirm this information 

with your state air pollution control agency or state small business

assistance program (for who to contact, see “Where can I get 

more information?”). If the screening process is not sufficient to

determine whether you are a major or minor source, use the 

procedures described below.

Material Usage VOC Content HAP Content

10% by weight

Ink 16,000 lbs/year (which = 0 lb/gal 10 lb VOC per

100 lb ink)

Cleaning Solvent 600 gal/year 6.9 lb/gal 0 lb/gal

Blanket Wash Solvent 500 gal/year 6.2 lb/gal 2.3 lb/gal toluene

Fountain Solution 250 gal/year 6.8 lb/gal 1.2 lb/gal ethylene glycol

Can I use EPA’s screening 

method to determine if 

I am a major or 

minor source?

Table 5. Maximum Usage and Pollutant Content of Inputs
23

EXAMPLE 2: PRINTING OPERATION

Because of the information you now know, which

includes: (1) your maximum capacity (or limits accepted from 

the state), and (2) the VOC content and the HAPs content of 

the materials you use (listed in your MSDS), using a materialbalance method is appropriate (assuming that all VOCs and 

HAPs are emitted). 

According to the MSDS, the VOC content of your ink can

vary from 5 to 10 percent by weight. Because potential to emit is

based on the assumption of maximum VOC content, you need to

use 10 percent.

According to the state small business assistance program,

your business is not required to include fugitive VOCs in potential

to emit calculations for a Title V permit. Fugitive HAPs, however,

do need to be included. By using the material balance method to

estimate potential to emit, you are assuming that all VOCs and

HAPs are emitted. Therefore, fugitive emissions and equipment

leaks are included in this estimate.

Determine your VOC emissions by using 

the following steps:

• Determine the potential to emit VOCs from each material used

(e.g., ink, solvents, solutions). To do this, multiply a material’s

usage by its VOC content (see Table 5 for usage and VOC content). 

• Add the individual VOC emissions together. The result will be

in pounds of VOCs per year. 

• Change from pounds of VOCs per year to tons of VOCs per year.

Do this by dividing the result you have by 2,000 (because there

are 2,000 pounds in 1 ton). 

You can use the equations summarized in Box 4 to carry

out the above steps:

Do I need to add in 

fugitive emissions or 

equipment leaks?

What method should I 

use to estimate my 

air emissions?

What is my potential to 

emit VOC emissions?
24

EXAMPLE 2: PRINTING OPERATION

VOC emissions, in tons/year 5

Step 1: Determine potential to emit VOCs from the ink, solvents, and solution:

Ink usage (from Table 5) 3 VOC content (from Table 5) 

(in lbs per year) (in lb of VOC per lb of ink) 

and also:

Solvent and solution usage (from Table 5) 3 VOC content (from Table 5) 

(in gal per year) (in lb of VOC per gal of 

solvents and solution)

Step 2: Add together the individual results for the ink, solvents, and solution:

lb VOC per yr 1 lb VOC per yr 1 lb VOC per yr 1 lb VOC per yr 

(from ink) (from the cleaning solvent) (from the blanket wash solvent) (from the fountain solution)

Step 3: Change from lb per year to tons per year:

total lb VOC per year 4 2000 5 tons total VOCs per year 

Cleaning solvent:

600 gal per yr of cleaning solvent 3 6.9 lb VOC per gal of cleaning solvent = 4,140 lb per year

(usage) (VOC content) of VOCs from the 

cleaning solvent

Blanket Wash Solvent:

500 gal per yr of blanket wash solvent 3 6.2 lb VOC per gal of blanket wash solvent = 3,100 lb per year of VOCs 

(usage) (VOC content) from the blanket

wash solvent

Fountain Solution:

250 gal per yr of fountain solution 3 6.8 lb VOC per gal of fountain solution = 1,700 lb per year 

(usage) (VOC content) of VOCs from the

fountain solution

Ink:

16,000 lb per yr of ink 3 10 lb of VOC per 100 lb of ink = 1,600 lb of VOCs 

(usage) (VOC content) per year from ink

Box 4. How to Determine Potential to Emit VOC Emissions 

Thus the VOC emissions from the ink are:

The VOC emissions from the solvents and solution are:

(Note that changing from pounds to tons per year will be done later.)
25

EXAMPLE 2: PRINTING OPERATION

To find the total VOC emissions from this printing 

business, add up all of the individual VOC emissions above as

shown in Box 5:

Box 5. Total Potential to Emit VOCs

This result shows that this printing company could be

only a minor source of VOC emissions (which can contribute to

criteria pollutants), since the maximum VOC emissions are less

than the major source level of VOCs, which is 50 tons per year.

Determine your potential to emit for HAP emissions in

the same way you did for VOC emissions. That is, for a particular

kind of HAP, first figure out separately the maximum HAPs that

could be emitted from each individual input material used (in this

case, the blanket wash solvent and fountain solution). Determine

your potential HAP emissions from each of these materials by

using the following steps:

• Determine the potential to emit HAPs from each material used

(e.g., solvents, solutions). To do this, multiply a material’s usage

by its HAP content (see Table 5 for usage and HAP content). 

• Change each individual HAP emission from pounds of HAP per

year to tons of HAP per year. Do this by dividing the result you

have by 2,000 (because there are 2,000 pounds in 1 ton). 

• Add the individual HAP emissions together to get total 

HAPs emissions.

You can use the equations summarized in Box 6 to 

carry out the above steps:

What is my total 

potential to emit for VOCs? 

Total Potential to Emit VOCs:

1,600 lb VOC per yr 1 4,140 lb VOC per yr 1 3,100 lb VOC per yr 1 1,700 lb VOC per yr 5 10,540 lb of total 

(from ink) (from cleaning solvent) (from blanket wash solvent) (from fountain solution) VOC per year

Now, change from lb of VOCs to tons of VOCs by dividing by 2,000: 10,540 4 2,000 5 5.27 tons per year of total VOCs

What is my potential to 

emit HAPs emissions?
26

EXAMPLE 2: PRINTING OPERATION

For this example, first figure out the potential to 

emit for the individual HAPs: toluene and ethylene glycol, 

listed in Table 5, as follows: 

Potential to Emit HAP Emissions

Step 1: Determine potential to emit HAPs from the solvents and solution:

Solvent and solution usage in gal per year 3 HAP content of the material in lb per gal of solvents and solution

Step 2: Change each HAP emission from lb per year to tons per year:

lb HAP per year 4 2000 5 tons HAP per year 

Step 3: Add together the individual results for the solvents and solution:

tons HAP per yr 1 tons HAP per yr 5 tons of total HAPs per year 

(from the blanket wash solvent) (from the fountain solution) 

Toluene from the blanket wash solvent:

500 gal per yr of blanket wash solvent 3 2.3 lb of toluene per gal of blanket wash solvent 5 1,150 lb 

(usage) (HAP content) of toluene per year

from the blanket

wash solvent

Change from pounds to tons: 1,150 lb of toluene per year 4 2000 5 0.575 ton toluene per year

Ethylene glycol from the fountain solution:

250 gal per yr of fountain solution 3 1.2 lb of ethylene glycol per gal of fountain solution 5 300 lb of ethylene glycol 

(usage) (HAP content) per year from the 

fountain solution

Change from pounds to tons: 300 lb of ethylene glycol per year 4 2000 5 0.15 ton ethylene glycol per year

Box 6. Potential to Emit HAP Emissions 
27

EXAMPLE 2: PRINTING OPERATION

To find the total HAP emissions from this printing 

business, add up all of the individual HAP emissions above, 

as follows:

This result shows that the printing company could be

only a minor source of HAP emissions, since its individual HAP

emissions all lie below 10 tons per year (which is the major

source level for individual HAPs), and its total HAP emissions

are less than 25 tons per year (which is the major source level 

for total HAPs).

No, the printing business in this example is not a major

source; it is a minor source of both VOC and HAP emissions

because its emissions fall below the major source levels for both

VOCs and HAPs.

What is my total potential 

to emit HAPs? 

Am I a major source of 

either VOC or 

HAP emissions?

Total Potential to Emit HAPs:

0.575 ton per yr 1 0.15 ton per yr 5 0.725 tons per year of total HAPs 

(of toluene from the blanket wash solvent) (of ethylene glycol from the fountain solution) 
28

WHERE CAN I GET MORE INFORMATION?

The Small Business Assistance Program has an Internet web site at:

http://www.epa.gov/ttn/sbap. Through this web site you can obtain

information pertinent to small businesses, including a list of small

business assistance program contacts (click on “Contacts and

Resources”). If you do not have access to the Internet, you can call

EPA’s Clean Air Technology Center Hotline at 919-541-0800 for a list

of state small business assistance program contacts or for more

information on potential to emit and related subjects. 

Also, the EPA’s Technology Transfer Network (TTN), available

through the Internet at: http://www.epa.gov/ttn, provides the 

public with a variety of air emissions materials, including the text

of the Clean Air Act, EPA guidance documents, and software. The

Small Business Assistance Program’s web site can also be accessed

from the TTN main home page (click on “Technical Sites,” then

click on “SBAP,” then click on “Contacts and Resources” for a list

of state small business assistance program contacts). The TTN

help-line number is (919) 541-5384.

The TTN web site also contains the EPA Office of Air and Radiation’s

Policy and Guidance site at: http://www.epa.gov/ttn/oarpg, which

contains policy memoranda on potential to emit and related topics

mentioned in this document. The references in Appendix C of 

this document also provide a partial list of relevant EPA guidance

documents and policy memoranda.

The CHIEF web site accessed through TTN provides information

on emission factors through resources such as AP-42 and the

Locating and Estimating series and through software such as the

Factor Information and Retrieval (FIRE) system. Software for some

emission models is available through the CHIEF web site.

Where can I get more information?
Appendix A

Definitions
Appendix A: Definitions

A-2

Attainment area: A geographical area that meets National Ambient

Air Quality Standards (NAAQS) for criteria air pollutants.

Criteria air pollutant: One of six air pollutants or classes of 

pollutants (see Table 1 in the text) regulated by the EPA for

which National Ambient Air Quality Standards (NAAQS) 

have been established.

Emission: Release of pollutants into the air (e.g., from a stack 

or duct).

Emission factor: A number that shows the relationship between

an air emission and a measure of production (e.g., pounds of SO2

per 1,000 gallons of input).

Fugitive emissions: Emissions resulting from leaks or from 

nonlocalized escape (e.g., from spraying operations).

Hazardous air pollutant (HAP): One of 188 hazardous air 

pollutants (see Appendix B) that are regulated.

Inherent limitation: A limitation on emissions that results from

unchanging and unavoidable physical constraints on the operation

of a business.

Major source: A business that has a potential to emit for a 

regulated pollutant (or class of pollutants) that is at or greater

than an emission threshold set by the government. The major

source threshold is 100 tons per year of any criteria pollutant if

the business is located in an attainment area. 

The major source thresholds for criteria pollutants for businesses

located in nonattainment areas are listed in Table 6 below.

Appendix A: Definitions
a Source: The Air Pollution Consultant, Sept./Oct. 1992

b tpy = tons per year

Major source thresholds for HAPs are listed in Table 7:

a tpy = tons per year

A-3

Appendix A: Definitions

Pollutant Nonattainment Area Classification Potential Emission Rate

Ozone Marginal 100 tpy VOCs or NOx

b

Moderate 100 tpy VOCs or NOx

Serious 50 tpy VOCs or NOx

Severe 25 tpy VOCs or NOx

Extreme 10 tpy VOCs or NOx

Transport regions not classified 50 tpy VOCs or 100 tpy NOx

as severe or extreme

Carbon monoxide Serious 50 tpy CO

Particulate matter < 10 mm Serious 70 tpy PM-10

(PM-10)

Pollutant Potential Emission Rate

Any single HAP 10 tpya

Total HAPs 25 tpy

Table 6. Major Source Thresholds for Criteria Pollutants in Nonattainment Areasa

Table 7. Major Source Thresholds for Hazardous Air Pollutants (HAPs)
A-4

Material-balance calculation: Calculation of emissions based on

the quantities and types of input materials and the quantities and

types of output materials.

Minor source: A business with a potential to emit that either

(1) lies below major source emission thresholds, or (2) lies

above major source emission thresholds, but through adoption

of emission or process controls or limitations, gains minor

source status. 

Nonattainment area: A geographical area that does not meet

National Ambient Air Quality Standards (NAAQS) for criteria

pollutants.

Potential to emit: The maximum capacity of a business to emit a

pollutant given its physical or operational design, and considering

certain controls and limitations.

Appendix A: Definitions
Appendix B

List of Hazardous Air Pollutants (HAPs)
B-2

Appendix B: HAPs Lista

CAS No. Chemical name

75-07-0 Acetaldehyde

60-35-5 Acetamide

75-05-8 Acetonitrile

98-86-2 Acetophenone

53-96-3 2-Acetylaminofluorene

107-02-8 Acrolein

79-06-1 Acrylamide

79-10-7 Acrylic acid

107-13-1 Acrylonitrile

107-05-1 Allyl chloride

92-67-1 Aminobiphenyl

62-53-3 Aniline

90-04-0 o-Anisidine

0 Antimony Compounds 

0 Arsenic Compounds (inorganic including arsine) 

1332-21-4 Asbestos

71-43-2 Benzene (including benzene from gasoline)

92-87-5 Benzidine

98-07-7 Benzotrichloride

100-44-7 Benzyl chloride

0 Beryllium Compounds

92-52-4 Biphenyl

117-81-7 Bis(2-ethylhexyl)phthalate (DEHP)

542-88-1 Bis(chloromethyl)ether

75-25-2 Bromoform

106-99-0 1,3-Butadiene

0 Cadmium compounds 

156-62-7 Calcium cyanamide

133-06-2 Captan

63-25-2 Carbaryl

a The Clean Air Act originally specified 189 hazardous air pollutants. In 1996, caprolactam was examined and taken off the list, and thus 

there are now 188 HAPs.
B-3

Appendix B: HAPs List

CAS No. Chemical name

56-23-5 Carbon tetrachloride

75-15-0 Carbon disulfide

463-58-1 Carbonyl sulfide

120-80-9 Catechol

133-90-4 Chloramben

57-74-9 Chlordane

7782-50-5 Chlorine

79-11-8 Chloroacetic acid

532-27-4 2-Chloroacetophenone

108-90-7 Chlorobenzene

510-15-6 Chlorobenzilate

67-66-3 Chloroform

107-30-2 Chloromethyl methyl ether

126-99-8 Chloroprene

0 Chromium Compounds 

0 Cobalt Compounds 

0 Coke Oven Emissions 

108-39-4 m-Cresol

95-48-7 o-Cresol

106-44-5 p-Cresol

1319-77-3 Cresols/Cresylic acid (isomers and mixture)

98-82-8 Cumene

0 Cyanide Compounds 

94-75-7 2,4-D, salts and esters

3547-04-4 DDE

334-88-3 Diazomethane

132-64-9 Dibenzofurans

96-12-8 1,2-Dibromo-3-chloropropane

84-74-2 Dibutylphthalate

106-46-7 1,4-Dichlorobenzene(p) 

91-94-1 3,3-Dichlorobenzidene

111-44-4 Dichloroethyl ether (Bis(2-chloroethyl)ether)

542-75-6 1,3-Dichloropropene 
B-4

Appendix B: HAPs List

CAS No. Chemical name

62-73-7 Dichlorvos

111-42-2 Diethanolamine

121-69-7 N, N-Diethyl aniline (N, N-Dimethylaniline)

64-67-5 Diethyl sulfate

119-90-4 3,3-Dimethoxybenzidine

60-11-7 Dimethyl aminoazobenzene

119-93-7 3,31⁄4-Dimethyl benzidine

79-44-7 Dimethyl carbamoyl chloride

68-12-2 Dimethyl formamide

57-14-7 1,1-Dimethyl hydrazine

131113 Dimethyl phthalate

77781 Dimethyl sulfate

534-52-1 4,6-Dinitro-o-cresol, and salts

51-28-5 2,4-Dinitrophenol

121-14-2 2,4-Dinitrotoluene

123-91-1 1,4-Dioxane (1,4-Diethyleneoxide)

122-66-7 1,2-Diphenylhydrazine

106-89-8 Epichlorohydrin (l-Chloro-2,3-epoxypropane)

106-88-7 1,2-Epoxybutane

140-88-5 Ethyl acrylate

100-41-4 Ethyl benzene

51-79-6 Ethyl carbamate (Urethane)

75-00-3 Ethyl chloride (Chloroethane)

106-93-4 Ethylene dibromide (Dibromoethane)

107-06-2 Ethylene dichloride (1,2-Dichloroethane)

107-21-1 Ethylene glycol

151-56-4 Ethylene imine (Aziridine)

75-21-8 Ethylene oxide 

96-45-7 Ethylene thiourea

75-34-3 Ethylidene dichloride (1,1-Dichloroethane)

0 Fine mineral fibers

50-00-0 Formaldehyde

0 Glycol ethers
B-5

Appendix B: HAPs List

CAS No. Chemical name

76-44-8 Heptachlor

118-74-1 Hexachlorobenzene

87-68-3 Hexachlorobutadiene

77-47-4 Hexachlorocyclopentadiene

67-72-1 Hexachloroethane

822-06-0 Hexamethylene-1,6-diisocyanate

680-31-9 Hexamethylphosphoramide

110-54-3 Hexane

302-01-2 Hydrazine

7647-01-0 Hydrochloric acid

7664-39-3 Hydrogen fluoride (Hydrofluoric acid)

123-31-9 Hydroquinone

78-59-1 Isophorone

0 Lead Compounds 

58-89-9 Lindane (all isomers)

108-31-6 Maleic anhydride

0 Manganese Compounds 

0 Mercury Compounds 

67-56-1 Methanol

72-43-5 Methoxychlor

74-83-9 Methyl bromide (Bromomethane)

74-87-3 Methyl chloride (Chloromethane)

71-55-6 Methyl chloroform (1,1,1-Trichloroethane)

78-93-3 Methyl ethyl ketone (2-Butanone)

60-34-4 Methyl hydrazine

74-88-4 Methyl iodide 

108-10-1 Methyl isobutyl ketone (Hexone)

624-83-9 Methyl isocyanate

80-62-6 Methyl methacrylate

1634-04-4 Methyl tert butyl ether

101-14-4 4,4-Methylene bis (2-chloroaniline)

75-09-2 Methylene chloride (Dichloromethane)

101-68-8 Methylene diphenyl diisocyanate (MDI)
B-6

Appendix B: HAPs List

CAS No. Chemical name

101-77-9 4,41⁄4-Methylenedianiline

91-20-3 Naphthalene

0 Nickel Compounds

98-95-3 Nitrobenzene

92-93-3 4-Nitrobiphenyl

100-02-7 4-Nitrophenol

79-46-9 2-Nitropropane

62-75-9 N-Nitrosodimethylamine

684-93-5 N-Nitroso-N-methylurea

59-89-2 N-Nitrosomorpholine

56-38-2 Parathion

82-68-8 Pentachloronitrobenzene (Quintobenzene)

87-86-5 Pentachlorophenol

108-95-2 Phenol

106-50-3 p-Phenylenediamine

75-44-5 Phosgene

7803-51-2 Phosphine

7723-14-0 Phosphorus

85-44-9 Phthalic anhydride 

1336-36-3 Polychlorinated biphenyls (Aroclors) 

0 Polycylic Organic Matter

1120-71-4 1,3-Propane sultone

57-57-8 beta-Propiolactone

123-38-6 Propionaldehyde 

114-26-1 Propoxur (Baygon) 

78-87-5 Propylene dichloride (1,2-Dichloropropane) 

75-56-9 Propylene oxide 

75-55-8 1,2-Propylenimine (2-Methyl aziridine)

91-22-5 Quinoline 

106-51-4 Quinone 

0 Radionuclides (including radon)

0 Selenium Compounds 

100-42-5 Styrene 
B-7

Appendix B: HAPs List

CAS No. Chemical name

96-09-3 Styrene oxide 

1746-01-6 2,3,7,8-Tetrachlorodibenzo-p-dioxin

79-34-5 1,1,2,2-Tetrachloroethane

127-18-4 Tetrachloroethylene (Perchloroethylene)

7550-45-0 Titanium tetrachloride 

95-80-7 2,4-Toluene diamine

584-84-9 2,4-Toluene diisocyanate

108-88-3 Toluene 

95-53-4 o-Toluidine

8001-35-2 Toxaphene (chlorinated camphene)

120-82-1 1,2,4-Trichlorobenzene

79-00-5 1,1,2-Trichloroethane

79-01-6 Trichloroethylene

95-95-4 2,4,5-Trichlorophenol

88-06-2 2,4,6-Trichlorophenol

121-44-8 Triethylamine

1582-09-8 Trifluralin

540-84-1 2,2,4-Trimethylpentane

108-05-4 Vinyl acetate

593-60-2 Vinyl bromide

75-01-4 Vinyl chloride

75-35-4 Vinylidene chloride (1,1-Dichloroethylene)

1330-20-7 Xylenes (isomers and mixture)

108-38-3 m-Xylenes

95-47-6 o-Xylenes

106-42-3 p-Xylenes

Appendix C

References
Appendix C:

References

C-2

Some of the EPA policy memoranda listed below and other 

guidance on potential to emit can be found on the Internet at

EPA’s Technology Transfer Network, Office of Air and Radiation

Policy and Guidance web site at:

http://www.epa.gov/ttn/oarpg

Metal Finishing Suppliers Association (MFSA). Air Emissions.

Chap. 2 in: Metal Finishing Guidance Manual. MFSA.

U.S. Environmental Protection Agency. 1998a. Potential to Emit

(PTE) Guidance for Specific Source Categories. April 14 policy

memorandum from J.S. Seitz, Office of Air Quality Planning and

Standards, and E. Schaeffer, Office of Regulatory Enforcement.

U.S. Environmental Protection Agency. 1998b. Technical Support

Document for Potential to Emit Guidance Memo. Documentation

of Emission Calculations. Tim Smith, Office of Air Quality

Planning and Standards. April.

U.S. Environmental Protection Agency. 1998c. Second Extension

of January 25, 1995 Potential to Emit Transition Policy and

Clarification of Interim Policy. July 10 memorandum from J.S.

Seitz and E.V Schaeffer.

U.S. Environmental Protection Agency. 1996a. Extension of

January 25, 1995 Potential to Emit Transition Policy. August 27

policy memorandum from J.S. Seitz, Office of Air Quality

Planning and Standards, and R.I. Van Heuvelen, Office of

Regulatory Enforcement.

U.S. Environmental Protection Agency. 1996b. Clarification of

Methodology for Calculating Potential to Emit (PTE) for Batch

Chemical Production Operations. August 29 policy memorandum

from J.S. Seitz, Office of Air Quality Planning and Standards.

U.S. Environmental Protection Agency. 1996c. Release of Interim

Policy on Federal Enforceability of Limitations on Potential to

Emit. January 22 policy memorandum from J.S. Seitz, Office 

of Air Quality Planning and Standards, and R.I. Van Heuvelen,

Office of Regulatory Enforcement.

U.S. Environmental Protection Agency. 1996d. Letter to

Subcommittee on Permits, New Source Review and 

Toxics Integration.

Appendix C: References
U.S. Environmental Protection Agency. 1995a. Options for

Limiting the Potential to Emit (PTE) of a Stationary Source 

under Section 112 and Title V of the Clean Air Act (Act). 

January 25 policy memorandum from J.S. Seitz, Office of Air

Quality Planning and Standards, and R.I. Van Heuvelen, Office 

of Regulatory Enforcement.

U.S. Environmental Protection Agency. 1995b. AP-42, 5th ed.,

Vol. 1. Compilation of Air Pollutant Emission Factors. Office 

of Air Quality Planning and Standards. January.

U.S. Environmental Protection Agency. 1995c. Calculating

Potential to Emit (PTE) for Emergency Generators. September 6

policy memorandum from J.S. Seitz, Office of Air Quality

Planning and Standards.

U.S. Environmental Protection Agency. 1995d. Calculating

Potential to Emit (PTE) and Other Guidance for Grain Handling

Facilities. November 14 policy memorandum from J.S. Seitz,

Office of Air Quality Planning and Standards.

U.S. Environmental Protection Agency. 1995e. Protocol for

Equipment Leak Emission Estimates. EPA-453/R-95-017.

U.S. Environmental Protection Agency. 1993a. The Plain 

English Guide to the Clean Air Act. Office of Air and Radiation. 

EPA 400-K-93-001. 

U.S. Environmental Protection Agency. 1993b. Approaches 

to Creating Federally Enforceable Emissions Limits. 

November 3 policy memorandum from J.S. Seitz, Office 

of Air Quality Planning.

U.S. Environmental Protection Agency. 1992. The Clean Air 

Act Amendments of 1990: A Guide for Small Businesses. Office 

of Air and Radiation. EPA 450-K-92-001.

C-3

Appendix C: References

State SBAP Contacts

If you don’t know the contact for the state small business assistance program in your state, you can find this information on the

Internet at: http://www.epa.gov/ttn/sbap or contact the Clean Air

Technology Center (CATC) at (919) 541-0800.

State SBAP contacts:

TECHNICAL REPORT DATA

(Please read Instructions on reverse before completing)

1. REPORT NO. 2.

EPA-456/B-98-003 

4. TITLE AND SUBTITLE 

Potential to Emit: A Guide for Small Businesses

7. AUTHOR(S)

9. PERFORMING ORGANIZATION NAME AND ADDRESS

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Information Transfer and Program Integration Division

Research Triangle Park, NC 27711 

12. SPONSORING AGENCY NAME AND ADDRESS 

Director

Office of Air Quality Planning and Standards

Office of Air and Radiation

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711 

15. SUPPLEMENTARY NOTES

EPA Work Assignment Manager: Deborah M. Elmore (919) 541-5437 

16. ABSTRACT

This document provides plain english guidance to owners and operators of small businesses on what is

potential to emit, and how to determine potential to emit for their facility. This document includes 

example calculations.

17. KEY WORDS AND DOCUMENT ANALYSIS 

a. DESCRIPTORS b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group 

Air Pollution Air Pollution control 

Potential to Emit 

Small Business 

Hazardous Air Pollutants 

VOC 

Particulate Matter 10. V.

18. DISTRIBUTION STATEMENT 19. SECURITY CLASS (Report) 21. NO OF PAGES

Release Unlimited Unclassified 46

20. SECURITY CLASS (Page) 22. PRICE 

Unclassified 

EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE

3. RECIPIENT’S ACCESSION NO. 

5. REPORT DATE 

October 1998 

6. PERFORMING ORGANIZATION CODE

8. PERFORMING ORGANIZATION REPORT NO.

10. PROGRAM ELEMENT NO.

11. CONTRACT/GRANT NO.

13. TYPE OF REPORT AND PERIOD COVERED

14. SPONSORING AGENCY CODE

EPA/200/04