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MEMORANDUM

Date: September 16, 2013

TO: Docket No. EPA-HQ-OAR-2012-0510: National Emissions Standards for 

Hazardous Air Pollutants for Flexible Polyurethane Foam Production

FROM: Kaye Whitfield, EPA/OAQPS/SPPD

SUBJECT: MACT-Allowable Emissions for the Flexible Polyurethane Foam Production Source 

Category

_________________________________________________________________________________

The purpose of this memorandum is to present analyses related to “MACT-allowable” 

emissions levels and risks for the Flexible Polyurethane Foam (FPUF) Production source category

that is being addressed under the EPA’s Residual Risk and Technology (RTR) review program. 

The RTR program is addressing the statutory requirements in section 112(f) and 112(d)(6) of 

the Clean Air Act for federal air toxics regulations. The regulations are National Emission Standards 

for Hazardous Air Pollutants (NESHAP) contained in 40 CFR part 63, which are commonly referred 

to as Maximum Achievable Control Technology (MACT) standards. The emissions data being used 

for the RTR risk assessment for this category consist of data representative of “actual” emission 

levels. In addition to the risks associated with these actual emission levels, the EPA also considers the 

levels of HAP emissions that facilities could emit and still be in compliance with the applicable 

MACT regulation. These emission levels are referred to as “MACT-allowable” emissions. The 

purpose of this memorandum is to discuss these MACT-allowable emission levels and to relate the 

potential risks if facilities emitted at these levels.

This memorandum is organized as follows. Section 1 presents the estimated maximum risk 

levels based on the actual emission levels for the source category, and Section 2 discusses the source 

category. Section 3 presents the approach to estimating the risks at the MACT-allowable levels. This 

is followed by a discussion of the estimation of the MACT-allowable emission level for the FPUF 

Production MACT standards in Section 4. Section 4 also includes a presentation of the estimated risks 

at the estimated MACT-allowable emissions levels.

1.0 Risk Levels Based on Actual Emissions

The estimated maximum inhalation risks for the source category are summarized in Table 1. 

These risks are based on actual emission levels.
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Table 1. Summary of Estimated Inhalation Risks for the FPUF Production Source Category

Based On Actual Emissions Levels

Source Category

Maximum individual 

cancer risk (in a 

million)1

Maximum 

chronic 

noncancer 

TOSHI2

Maximum acute 

HQ3

Flexible Polyurethane Foam 

Production (FPUF) 0.7 0.9 0.9

1 Maximum individual excess lifetime cancer risk.

2 Maximum target organ specific hazard index (TOSHI). The maximum TOSHI is based on 

respiratory effects. 

3 Maximum acute Hazard Quotient (HQ).

2.0 Source Category Background

The FPUF Production MACT standards address three subcategories of FPUF production facilities: 

slabstock foam production facilities, molded foam production facilities, and rebond foam production 

facilities. We estimate there are currently 7 slabstock foam production facilities, 6 molded foam 

production facilities, and 2 rebond foam production facilities (these 2 rebond facilities are co-located 

with other slabstock or molded foam facilities) operating in the U.S. that are subject to the FPUF 

Production MACT standards. For these different facility types, the FPUF production MACT 

standards include requirements for the following types of emission sources: (1) storage vessels, (2) 

equipment leaks, (3) foam production lines, (4) equipment cleaning, and (5) mold release agents. 

Table 2 summarizes the formats of the standards for these emission points. 

Table 2. Formats of Standards for the FPUF Production NESHAP

FPUF Production 

Subcategory Emission Source Type Format of Primary Standard

Slabstock Storage Vessels Equipment Standards, Work Practice Standards

Equipment Leaks Equipment Standards, Work Practice Standards

Production Line Performance Standard (HAP Auxiliary Blowing 

Agent (ABA) formulation limits)

Equipment Cleaning HAP Use Prohibitiona

Source-wide emission 

limit alternative

Alternative limit for all HAP ABA storage, 

equipment leaks, equipment cleaning and production 

line emissions 

Molded Equipment Cleaning HAP Use Prohibitionb

Mold Release Agents HAP Use Prohibition

Rebond Equipment Cleaning HAP Use Prohibition

Mold Release Agents HAP Use Prohibition a The NESHAP contains an exception that allows HAP to be used in cleaning if the same HAP is used 

as an ABA and for cleaning equipment and if the source-wide emission limit alternative is chosen. 

b The NESHAP contains an exception that allows diisocyanates to be used to flush certain equipment 

during startup or maintenance if the diisocyanates are in a closed-loop system and are re-used in 

production. 
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With the MACT standards in place, there are no HAP emissions allowed from equipment cleaning or 

mold release operations at molded and rebond foam production facilities. For slabstock foam 

production, HAP emissions of toluene diisocyanate (TDI), which is used in the foam production 

chemical reaction, are expected from storage vessels, equipment leaks and the production line. The 

MACT standards also contain requirements that restrict the amount of HAP that can be used as an 

auxiliary blowing agent (ABA). Emissions of methylene chloride, the primary HAP ABA used, 

would be expected from storage vessels, equipment leaks, and the production line. However, since 

the compliance date of the MACT standards, all operating slabstock foam production facilities in the 

U.S. have stopped using methylene chloride as an ABA, and none currently use any HAP as an ABA.

3.0 Approach to Estimating Risks from MACT-allowable Emission Levels

The approach to estimate the risks from MACT-allowable emission levels was to first estimate 

the relationship between the actual and MACT-allowable emission levels, and then to estimate the 

potential risk impacts from the differences between actual and MACT-allowable emissions. In 

general, the risk impact was assumed to be proportional to the difference in emission levels. For 

example, if MACT-allowable emissions were estimated to be three times as high as actual emissions, 

it was assumed that risks could be as much as three times as high as those estimated from the 

modeling conducted using actual emissions. The assumption regarding the linear relationship between 

emissions and risks is generally reasonable for chronic cancer and noncancer risks. However, using 

this approach for acute risks would likely overestimate the impacts, as the acute risk estimate already 

has numerous built in conservative assumptions. 

This general approach is valid where HAP emissions are present in the actual emissions-level data 

used in the risk modeling and only differences in the proportion of HAP emitted exist; however, this 

approach is not appropriate where HAP in the actual emissions-level data are entirely missing. As 

explained in Section 2.0 of this document, the industry has stopped using HAP as auxiliary blowing 

agents (ABAs) in slabstock foam production, but the MACT standards allow the use of HAP as ABAs 

in the production of this foam. As there are no HAP ABAs in the current actual emissions-level data 

used for risk modeling, additional modeling was required to determine the risks that would be present 

at the MACT-allowable level of HAP ABA use. For the facilities that produce slabstock foam, HAP 

ABA emissions were estimated for each facility based on emissions information gathered during 

development of the MACT standards. These emissions were then assigned appropriate emissions 

release parameters for each facility and modeled using the same modeling procedures and tools as that 

used for modeling with actual emissions. The product of this is an estimate of cancer risks, chronic 

non-cancer risks and acute exposure risks associated with HAP ABA emissions at the MACTallowable level for slabstock foam production facilities. 

4.0 Results of Analysis

Equipment Cleaning and Mold Release Agents

The ability to estimate MACT-allowable emissions for specific emission points, or for specific 

emission point types, is largely dependent on the format of the standards. For emission source types 

which have prohibitions on the use of HAP, including the use of HAP in equipment cleaning and the

use of HAP as a mold release agent, there would be no difference between actual and MACTallowable emissions, provided the facilities are complying with the rule. We have no information to 
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suggest facilities are not complying with the MACT standards for these emission source types; 

therefore, we believe the actual emissions levels are equal to the allowable emissions levels for these 

emission source types. As these are the only regulated emissions source types at molded and rebond 

foam facilities, we believe actual emissions are equal to the allowable emissions levels for these 

facility types. 

Storage Vessels and Equipment Leaks

For slabstock foam facilities, there are work practices and equipment standards for storage vessels 

containing diisocyanates and HAP ABA. There are also work practices and equipment standards for 

diisocyanate equipment leaks and work practices for HAP ABA equipment leaks, with an option to 

use specified equipment rather than perform the work practices for pumps in HAP ABA service. For 

work practice standards and equipment standards, there would be no difference between actual and 

MACT-allowable emissions for emission sources, provided the facilities are not conducting additional 

work practices, are not using equipment proven to reduce emissions beyond those required in the rule, 

and the equipment is maintained properly and is in good working condition (as required). For 

diisocyanate storage vessels and equipment leaks, we are not aware of any situations where additional 

work practices or equipment are used or are not properly maintained at the facilities in this source 

category. Therefore, for these storage vessels and equipment leaks, we believe that the actual 

emission levels are a reasonable estimation of the levels allowed by the MACT standards. We have 

learned that facilities in this source category have stopped using HAP ABAs, and therefore, are no 

longer storing these materials or having equipment leaks of HAP ABA. Consequently, the amount of 

emissions allowed by the MACT standards is higher than the actual amount emitted. An estimate of 

the MACT-allowable amount of HAP ABA emissions is discussed further below, in the context of the 

total HAP ABA emissions at slabstock FPUF production facilities.

Slabstock Foam Production Lines

For the foam production line at slabstock FPUF production facilities, the MACT standards include

HAP ABA formulation limits that restrict the amount of HAP ABA that can be used, depending on 

the grade and amount of each grade of foam produced. For each grade of foam produced, HAP ABAs 

could be emitted on a spectrum based on the amount of HAP ABA actually used. Facilities could be 

using the maximum amount of HAP ABA allowed by the standards, less than the maximum amount 

of HAP ABA allowed, due to use of substitute non-HAP ABAs or other types of processes that do not 

require as much ABA, or zero HAP ABA if a facility chooses to use only non-HAP ABAs or 

processes that do not require the use of ABAs. We have determined through contact with industry 

representatives, that no facilities in the slabstock foam industry in the U.S. currently use HAP ABAs. 

Therefore, the MACT standards allow the use of HAP ABAs, but actual emissions of HAP ABAs are 

currently zero. Since facilities have stopped using HAP as ABAs, they are no longer storing these 

chemicals or using them in process equipment. Therefore, there are also currently no HAP ABA 

emissions from storage vessels or equipment leaks. 

While we do not have information on the grades of foam produced at each facility or the amounts of 

HAP ABA that could be used at each, we have developed an estimate of the HAP ABA emissions for 

a general facility based on data used during development of the MACT standards. To determine costs 

and environmental impacts of regulatory alternatives, during the FPUF Production MACT standards 

development, five model plants were developed based on available information, including company 

responses to information collection requests, site visit observations, and information received from 

industry trade group associations, vendors, and company representatives. The estimates of HAP ABA 
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emissions before implementation of the MACT standards for these model plants were based on the 

number and size of HAP ABA storage vessels, the number of components in HAP ABA service, the 

number of foam production lines, production line speed, and amounts of various grades of foam 

produced. Assuming that the HAP ABA chemical was also used to clean equipment, HAP ABA 

emissions were estimated for the model plants as shown in Table 3. As a result of the implementation 

of the MACT standards, the EPA estimated HAP ABA emissions would be reduced by 69%.a The 

estimated HAP ABA emissions remaining after MACT implementation are also shown in Table 3.

Table 3. Model Plant HAP ABA Emissions Estimates1

Model 

Plant

Total Estimated HAP 

ABA Emissions (TPY)

Pre-MACT 

HAP ABA 

Storage 

Emissions 

(TPY)

Pre-MACT 

HAP ABA 

Production 

Line 

Emissions 

(TPY)

Pre-MACT 

HAP ABA 

Equipment 

Cleaning 

Emissions 

(TPY)

Pre-MACT 

HAP ABA 

Equipment 

Leaks 

Emissions 

(TPY)

PreMACTPostMACT

1 64 20 0.09 55 5 3.5

2 174 64 0.26 165 5 3.5

3 339 105 0.52 330 5 3.5

4 343 106 0.03 335 5 3.5

5 388 120 0.03 380 5 3.5

1 “Hazardous Air Pollutant Emissions from the Production of Flexible Polyurethane Foam. Basis and 

Purpose Document for Proposed Standards.” Tables 7-1 and 8-2. U.S. EPA Office of Air Quality 

Planning and Standards. September 1996.

The estimated post-MACT implementation HAP ABA emissions range from 20 tons per year (TPY) 

per facility to 120 TPY per facility. We assume these are the levels of HAP ABA emissions typical 

facilities of various sizes and foam production volumes would emit at the MACT-allowable level. As 

we do not have data regarding current production volumes and grades of foam produced, it is not 

possible to determine which model facility represents the currently operating slabstock foam 

production facilities. Therefore, we have assumed the median model, Model Plant 3, approximates 

the typical slabstock production facility and is likely representative of the currently operating 

slabstock production facilities. As such, we estimate that the MACT-allowable HAP ABA emissions 

at slabstock production facilities are 105 TPY per facility, whereas actual HAP ABA emissions are 0 

TPY for each of these facilities. 

To estimate risks considering MACT-allowable emissions at slabstock foam production facilities, we 

developed risk modeling inputs for HAP ABA. As methylene chloride was the most commonly used 

HAP ABAa

, we assumed that all HAP ABA was methylene chloride. We also assumed there was one 

fugitive release point of methylene chloride, to account for emissions from equipment leaks, storage 

vessels and equipment cleaning; and one point source emissions release point, to account for 

methylene chloride emissions from a foam production line roof stack. The fugitive emissions release 

point was assumed to be 3% of the total HAP ABA emissions, or 3 TPY of methylene chloride, based 

on the pre-MACT HAP ABA emissions from storage vessels, equipment leaks and equipment 

cleaning totaling 9 TPY, reduced to 3 TPY with MACT controls. The point source emissions release 

 

a Hazardous Air Pollutant Emissions from the Production of Flexible Polyurethane Foam. Basis and Purpose Document 

for Proposed Standards.” Page 6-9. U.S. EPA Office of Air Quality Planning and Standards. September 1996.
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point was assumed to have 97% of the total HAP ABA emissions, or 102 TPY of methylene chloride, 

based on the pre-MACT HAP ABA emissions from the foam production line of 330 TPY reduced to 

102 TPY with MACT controls. The model emissions release point parameters and locations were 

based on other FPUF production emission point parameters and locations at each slabstock production 

facility. The emissions and emission point parameters used for modeling the MACT-allowable HAP 

ABA emissions are included in the Appendix to this document. 

In summary, the MACT-actual to MACT-allowable emissions levels relationship for each FPUF 

regulated emissions source type is shown in Table 4. The estimated risks based on the MACTallowable emissions is shown in Table 5.

Table 4. PFUF Emission Source Type MACT-Actual to MACT-Allowable Emissions Summary

FPUF Production 

Subcategory Emission Source Type Actual to Allowable Emissions Relationship

Slabstock Storage Vessels - Diisocyanates Actual = Allowable Equipment Leaks - Diisocyanates

Storage Vessels – HAP ABA

Actual < Allowable; Allowable 

Emissions Estimated from Model Plant 

Information

Equipment Leaks – HAP ABA

Production Line – HAP ABA

Equipment Cleaning – HAP ABA

Source-wide emission limit 

alternative

Molded Equipment Cleaning

Actual = Allowable Mold Release Agents

Rebond Equipment Cleaning

Mold Release Agents

Table 5. Summary of Estimated Inhalation Risks for FPUF Production Based On MACTAllowable Emissions Levels

Actual MACT-Allowable

Source 

Category

Maximum 

individual 

cancer 

risk (in a 

million)

Maximum 

chronic 

noncancer 

TOSHI

Maximum 

acute HQ

Maximum 

individual 

cancer 

risk (in a 

million)

Maximum 

chronic 

noncancer 

TOSHI

Maximum 

acute HQ

FPUF 

Production 0.7 0.9 0.9 5 0.9 4
DRAFT – DO NOT QUOTE OR CITE

A-1

Appendix

MACT-allowable HAP ABA Emissions and Emission Point Parameters

FACILITY NAME CITY STATE EMISSION UNIT ID

POLLUTANT 

DESCRIPTION

EMISSIONS 

(TPY)

STACK 

HEIGHT 

(FT)

EXIT GAS 

TEMPERA

TURE (F)

STACK 

DIAMETE

R (FT)

EXIT GAS 

VELOCITY 

(FT/S)

FUGITIVE 

LENGTH 

(FT) 

FUGITIVE 

WIDTH 

(FT)

FUGITIVE 

ANGLE 

DEGREES

LONGITUDE 

COORDINATE

LATITUDE 

COORDINATE

PREMIER FOAM INC. NEWNAN GA HAP ABA allowable fugitive emissions Methylene Chloride 3 10 72 0.003 0.0003 50 65 0 -84.792813 33.345083

PREMIER FOAM INC. NEWNAN GA HAP ABA allowable point emissions Methylene Chloride 102 35.69408 168.7812 1.941379 30.57371 -84.792813 33.345083

FOAMEX, L.P. FT. WAYNE IN HAP ABA allowable fugitive emissions Methylene Chloride 3 10 72 0.003 0.0003 45 75 92 -85.176306 41.007313

FOAMEX, L.P. FT. WAYNE IN HAP ABA allowable point emissions Methylene Chloride 102 23 80 3.7 22 -85.17694 41.007287

FOAMEX L.P. AUBURN IN HAP ABA allowable fugitive emissions Methylene Chloride 3 11 72 0.003 0.0003 50 65 73 -85.064972 41.349025

FOAMEX L.P. AUBURN IN HAP ABA allowable point emissions Methylene Chloride 102 28 94 8.9 5 -85.064693 41.349533

Flexible Foam Products Inc Tupelo MS HAP ABA allowable fugitive emissions Methylene Chloride 3 10 72 0.003 0.0003 50 65 0 -88.685946 34.230915

Flexible Foam Products Inc Tupelo MS HAP ABA allowable point emissions Methylene Chloride 102 40 86 4 79.6 -88.685946 34.230915

Hickory Springs Manufacturing Conover NC HAP ABA allowable fugitive emissions Methylene Chloride 3 10 72 0.003 0.0003 50 65 0 -81.241851 35.71747

Hickory Springs Manufacturing Conover NC HAP ABA allowable point emissions Methylene Chloride 102 95 77 3.5 27.6 -81.241851 35.71747

Foamex International, Inc. Cornelius NC HAP ABA allowable fugitive emissions Methylene Chloride 3 10.75 72 0.003 0.0003 37 105 325 -80.849265 35.465719

Foamex International, Inc. Cornelius NC HAP ABA allowable point emissions Methylene Chloride 102 75 100 1 135 -80.849875 35.466756

FOAMEX LP/CORRY CORRY PA HAP ABA allowable fugitive emissions Methylene Chloride 3 30 72 0.003 0.0003 50 65 0 -79.616216 41.916883

FOAMEX LP/CORRY CORRY PA HAP ABA allowable point emissions Methylene Chloride 102 30 70 3 20 -79.614119 41.916276