1

Memorandum

To: Docket EPA-HQ-OAR-2014-0198

From: Margaret Sheppard

EPA/Stratospheric Protection Division

Subject: Information on workplace exposure limits for foam blowing agents

Date: July 7, 2014

This document summarizes information on workplace exposure limits for foam blowing 

agents mentioned in the preamble to the proposed rule, “Protection of Stratospheric Ozone: 

Change of Listing Status for Certain Substitutes under the Significant New Alternatives 

Policy Program.”

Table 1 provides the meaning of a number of abbreviations and terms that will be used 

later in this document. Table 2 identifies the workplace exposure limits for the foam blowing 

agents mentioned in the preamble, as well as setting out the foam blowing agents that are 

acceptable by end-use. HCFC foam blowing agents are not included here; these foam blowing 

agents are restricted under EPA’s phaseout regulations implementing Section 605(a). 
2

Table 1. Explanation of Exposure Limit-Related Terminology1

Organizations Issuing Workplace Exposure Limits

Abbreviation Full Name of Organization

OSHA Occupational Safety and Health Administration

NIOSH National Institute for Occupational Safety and Health

ACGIH American Conference of Governmental Industrial Hygienists

AIHA American Industrial Hygiene Association

Workplace Exposure Limits

Abbreviation Name of Exposure Limit Explanation

Short-Term Exposure

STEL Short-Term Exposure Limit A 15-minute time-weighted average (TWA) exposure that should not be 

exceeded at any time during a workday, even if the 8-hour TWA exposure is 

within the 8-hour Threshold Limit Value (TLV)–TWA set by ACGIH. 

(OSHA may also set a STEL).

Excursion Limit2Excursion Limit Where a compound does not have a TLV-short-term exposure limit, an 

excursion limit may be applied. Excursions in worker exposure levels may 

exceed 3 times the TLV-TWA for no more than a total of 30 minutes during 

a workday, and under no circumstances should they exceed 5 times the TLVTWA, provided that the TLV-TWA is not exceeded according to ACGIH. 

Long-Term Exposure

AEL Acceptable Exposure Limit This is a recommended workplace exposure limit, typically an 8-hour TWA 

exposure limit. Manufacturers may recommend an AEL for their products, 

particularly where there is not an industry recommendation such as a TLV or 

Workplace Environmental Exposure Limit (WEEL) or where there is no 

permissible exposure limit (PEL) from OSHA.

PEL Permissible Exposure Limit This is a mandatory 8-hour time-weighted average exposure limit set by

OSHA. 

REL Recommended Exposure 

Limit

This is a recommended 10-hour TWA exposure limit set by NIOSH.

TLV-TWA Threshold Limit Value –

Time-Weighted Average

The TWA concentration for a conventional 8-hour workday and a 40-hour 

workweek, to which it is believed that nearly all workers may be repeatedly

exposed, day after day, for a working lifetime without adverse effect 

according to ACGIH. 

WEEL Workplace Environmental 

Exposure Limit

The TWA concentration for a conventional 8-hour workday and a 40-hour 

workweek, to which it is believed that nearly all workers may be repeatedly

exposed, day after day, for a working lifetime without adverse effect 

according to AIHA.

 

1 All information in this table taken from EPA (1994) except where otherwise noted.

2 ACGIH (2004)
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Table 2. 8-Hour Workplace Exposure Limits and End-Uses for Substitute Flow Blowing Agents

Substitute

Exposure Limit 

Information

Listing for Substitute, by End-Use

8-hr TWA 

Workplace 

Exposure 

Limit in parts 

per million 

(ppm)

Abbreviation 

for Type of 

Limit

Rigid 

Polyurethane (PU) 

& Polyisocyanurate 

Laminated 

Boardstock

Rigid PU, 

Appliance1

Rigid PU, 

Spray1

Rigid PU, 

Commercial Ref 

& Sandwich 

Panels1

Rigid PU, 

Slabstock1

Polystyrene, 

Extruded 

Boardstock & 

Billet (XPS)

Phenolic 

Insulation 

Board & 

Bunstock

Integral 

Skin PU1, 2

Polystyrene

Extruded 

Sheet

Flexible 

PU Polyolefin3

Water

N/A N/A



        

CO2

5000 PEL



        

HFC-134a

1000 WEEL

X X

X

X X X X X X X X

HFC-152a

1000 WEEL



         

HFC-245fa

200 WEEL

X X



X

X

X X X X X X

HFC-365mfc

1000 Manufacturer 

(Mfr) AEL X

X X

X

X X X X X X

Commercial blends 

of 7-13% HFC227ea and 

remainder HFC365mfc

1000 Mfr AEL

 X

HFO-1234ze

800 WEEL         

Exxsol Blowing 

Agents

600 TLV



    



  

Saturated Light 

Hydrocarbons C3-

C6

(e.g., n-pentane)

600 to 1000 TLV

        

Formic Acid

5 PEL   



Acetone

250/500 REL/TLV

 

Methyl Formate

100 PEL     

2-Chloropropane

350 EPA AEL




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Table 2. 8-Hour Workplace Exposure Limits and End-Uses for Substitute Flow Blowing Agents

Substitute

Exposure Limit 

Information

Listing for Substitute, by End-Use

8-hr TWA 

Workplace 

Exposure 

Limit in parts 

per million 

(ppm)

Abbreviation 

for Type of 

Limit

Rigid 

Polyurethane (PU) 

& Polyisocyanurate 

Laminated 

Boardstock

Rigid PU, 

Appliance1

Rigid PU, 

Spray1

Rigid PU, 

Commercial Ref 

& Sandwich 

Panels1

Rigid PU, 

Slabstock1

Polystyrene, 

Extruded 

Boardstock & 

Billet (XPS)

Phenolic 

Insulation 

Board & 

Bunstock

Integral 

Skin PU1, 2

Polystyrene

Extruded 

Sheet

Flexible 

PU Polyolefin3

Vacuum Panels

N/A N/A



Blends of HFC365mfc and at 

least 5% HFC245fa

200 to 1000 Mfr AEL



Ecomate

100 PEL



        

Formacel B 1000 Mfr AEL X

Formacel TI 1000 Mfr AEL X X X X X X X

Formacel Z-6

1000 Mfr AEL X

X

X X X X X

HFC152a/Saturated 

Light Hydrocarbon 

Blends

600 to 1000 WEEL/TLV



Trans-1-chloro3,3,3-trifluoroprop-1-ene 

(SolsticeTM LBA)

800 WEEL

     

1. - Acceptability listings include blends of acceptable substitutes in these end-uses.

2. - Under the Section 610 Non-Essential Use Ban, the sale and distribution or offer for sale and distribution of polyolefin foam manufactured with HCFCs is banned except for closed cell rigid polyethylene foam when such foam is suitable in shape, thickness and design to be used as a 

product that provides insulation around pipes used in heating, plumbing, refrigeration, or industrial process systems 

KEY: Currently Acceptable

Proposed unacceptable

 Currently no listing



X
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References

ACGIH 2004. The Documentation of the Threshold Limit Values and Biological Exposure Indices. American Conference of 

Governmental Industrial Hygienists. Available online at: www.acgih.org. 

EPA 1994. Significant New Alternatives Policy Technical Background Document: Risk Screen on the Use of Substitutes for Class I

Ozone-depleting Substances: Refrigeration and Air Conditioning. Stratospheric Protection Division. March, 1994.