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Significant New Alternatives Policy Program

Foam Blowing Sector

Risk Screen on Substitutes in Rigid Polyurethane Appliance Foam; Rigid Polyurethane 

Commercial Refrigeration and Sandwich Panels; Rigid Polyurethane & Polyisocyanurate 

Laminate Boardstock; Rigid Polyurethane Slabstock; Flexible Polyurethane; Integral Skin 

Polyurethane

Substitute: Methylal (Dimethoxymethane)

This risk screen does not contain Clean Air Act (CAA) Confidential Business Information (CBI) 

and, therefore, may be disclosed to the public.

1. INTRODUCTION

Ozone-depleting substances (ODS) are being phased out of production in response to a series of 

diplomatic and legislative efforts that have taken place over the past decade, including the Montreal 

Protocol and the Clean Air Act Amendments of 1990 (CAAA). The U.S. Environmental Protection 

Agency (EPA), as authorized by Section 612 of the CAAA, administers the Significant New Alternatives 

Policy (SNAP) Program, which identifies acceptable and unacceptable substitutes for ODS in specific 

end-uses based on assessment of their health and environmental impacts. 

EPA’s decision on the acceptability of a substitute is based on the findings of a screening assessment of 

potential human health and environmental risks posed by the substitute in specific applications. EPA has 

already screened a large number of substitutes in many end-uses within all of the major ODS-using 

sectors, including refrigeration and air conditioning, solvent cleaning, foam blowing, aerosols, fire 

suppression, adhesives, coatings and inks, and sterilization. The results of these risk screens are presented 

in a series of Background Documents that are available in EPA's docket.

The purpose of this risk screen is to supplement EPA’s Background Document on the foam blowing

sector (EPA 1994) (hereinafter referred to as the Background Document). This risk screen evaluates the 

potential use of methylal (also known as dimethoxymethane) in rigid polyurethane appliance foam; rigid 

polyurethane commercial refrigeration and sandwich panels; rigid polyurethane & polyisocyanurate 

laminate boardstock; rigid polyurethane slabstock; flexible polyurethane; and integral skin polyurethane.

Table 1 presents information on the composition of the proposed substitute.
 

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Table 1. Composition of Methylal

Constituent Chemical 

Formula CAS Number Percent of Total(by weight)a

Methylal (Dimethoxymethane) C3H8O2 109-87-5 >99.49%

Potential Impurities (maximum concentration)

aNote that less than 0.51 percent of methylal is composed of impurities. These impurities are reasonably anticipated to be present when the 

proposed substitute is manufactured for commercial purposes; however, these impurities are not thought to be present in quantities sufficient to 

pose a risk to humans or to the environment. 

The potential risks associated with use of foam blowing agents have been examined at length in the 

Background Document. The reader is referred to this reference for a detailed discussion of the 

methodologies used to conduct this risk screen. This risk screen addresses flammability risk and assesses 

the impact of potential releases of methylal on the atmosphere and climate. Occupational exposure was 

modeled to ensure that manufacture and application of the proposed substitute in the proposed foam 

blowing end-uses does not pose unacceptable risk to workers. Lastly, general population exposure 

modeling was performed to ensure that the proposed substitute would not pose an unacceptable risk to the 

population at large. 

Section 2 of this report summarizes the results of the risk screen for the proposed substitute listed in Table 

1. The remainder of the report is organized into the following sections:

 Section 3: Atmospheric Assessment

 Section 4: Volatile Organic Compound Assessment

 Section 5: Potential Health Effects

 Section 6: Flammability Assessment

 Section 7: Occupational Exposure Assessment

 Section 8: End-Use Exposure Assessment

 Section 9: General Population Exposure Assessment

 Section 10: References

2. SUMMARY OF RESULTS

Methylal is recommended for SNAP approval as a foam blowing agent in the following end-uses: rigid 

polyurethane appliance foam; rigid polyurethane commercial refrigeration and sandwich panels; rigid 

polyurethane & polyisocyanurate laminate boardstock; rigid polyurethane slabstock; flexible 

polyurethane; and integral skin polyurethane. EPA's risk screen indicates that the use of the proposed 

substitute will be less harmful to the atmosphere than the continued use of CFC-11, HCFC-141b, HCFC142b, and HCFC-22, as well as other commonly used blowing agents. According to the Material Data 

Safety Sheet (MSDS), methylal is highly flammable. Therefore, personnel should ensure that the 

substitute is not exposed to high temperatures, sparks, or open flames, as directed in the substitute’s 

MSDS during use. Given that appropriate personal protective equipment (PPE) consistent with 

Occupational Safety & Health Administration (OSHA) guidelines and engineering controls (e.g., exhaust 

ventilation, vapor-in-air detection systems) will be used during installation, maintenance, and disposal 

activities, no significant risks to workers or the general population are expected.
 

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3. ATMOSPHERIC ASSESSMENT

This section presents an assessment of the potential risks to atmospheric integrity posed by the use of 

methylal as a foam blowing agent. The ozone depletion potential (ODP), global warming potential 

(GWP), and atmospheric lifetime (ALT) of the proposed substitute are presented in 

Table 2. As compared to blowing agents used in these end-uses, such as CFC-11, HCFC-141b, HCFC142b, and HCFC-22, methylal is substantially less harmful to the ozone layer, has less climate impact, 

and a shorter atmospheric lifetime. In addition, methylal also has lower climate impact and a shorter 

atmospheric lifetime than those for other substitutes examined in the Background Document. Thus, EPA 

believes that use of methylal would result in substantially less harm to the climate and ozone layer than 

the continued use of ODS and other commonly used foam blowing agents.

Table 2. Atmospheric Impacts of Methylal Compared to CFC-11, HCFC-141b, HCFC-142b, and 

HCFC-22

Refrigerant ODPa GWPb ALT (years)b

Methylal 0 2.2 daysa

CFC-11 1 4,750 45

HCFC-141b 0.11 725 9.3

HCFC-142b 0.065 2,310 17.9

HCFC-22 0.055 1,810 12

HFC-134a 0 1,430 14

HFC-245fa 0 1,030 7.6

a WMO (2011)

b IPCC 4th Assessment Report (Forster, et al 2007)

4. VOLATILE ORGANIC COMPOUND ASSESSMENT

Methylal is regulated as a volatile organic compound (VOC) under the CAA (40 CFR 51.100(s)). 

Through regulations and standard industry practices, emissions of methylal should be controlled. An 

assessment was performed to compare the annual VOC emissions from use of methylal in the foam 

blowing end-uses in one year to other anthropogenic sources of VOC emissions. Assuming the 

submitter’s maximum annual production of methylal for all proposed foam blowing sector end-uses is 

entirely released, approximately [ ] MT of VOCs would be emitted. This is approximately equal to [ ]

percent of all anthropogenic VOC emissions from 2013 in the U.S.;

1 however, the release of total 

production for all foam blowing end-uses is extremely unlikely to occur. Thus, an additional analysis was 

performed to determine likely annual VOC emissions from use of methylal in the foam blowing sector. 

Table 3 summarizes leak estimates and market penetrations from the Vintaging Model for the proposed 

foam blowing end-uses.

 

1 Based on the 2013 annual total VOC emissions for the U.S. (i.e., approximately 16.1x106 MT) as reported in the National 

Emissions Inventory (EPA 2014).
 

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Table 3. Foam Release Rates and Market Penetrations by End-Use

Foam End-Use Annual Leak 

Rate First Year Lossa Disposal Loss Lifetime (yrs)

Average Annual 

Release Rateb

Market 

Share

PU Rigid – Commercial 

Refrigeration 0.25% 6% 90.25% 15 6% 1%

PU Rigid – Slabstock 0.75% 37.5% 51.25% 15 6% 1%

PU Rigid – Appliance 0.25% 3.75% 40% 14 3% 11%

PU Rigid – Sandwich 

Panels 0.50% 5.5% 69.5% 50 2% 2%

PU Rigid – Boardstock 1% 6% 44% 50 1% 66%

Flexible PU - Slabstock 0% 100% 0% 1 100% 1%

Flexible PU – Integral 

Skin 2.5% 95% 0% 2 49% 0%

Source: Vintaging Model (v4.4_7.29.14).

a First year losses include losses at manufacture and other production steps that occur prior to end-use.

b Calculated as (Leak Rate + First Year Loss + Disposal Loss)/Lifetime

Assuming the average annual release rates for each of those end-uses, and that use of methylal is 

distributed according to existing market share for each proposed foam end-use,

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approximately 1 MT of 

VOCs would be expected to be released into the atmosphere per year. This amount is approximately 

6.2x10-6 percent of all anthropogenic VOC emissions. In addition, the end-uses with the greatest annual 

release rate (e.g., integral skin and flexible polyurethane slabstock) are reasonably expected to occur 

indoors in a manufacturing or disposal facility, which would have engineering controls in place (e.g.,

carbon adsorption systems or scrubbers) such that actual quantities of methylal emissions would be less 

than the quantity calculated in this assessment. 

Thus, use of methylal would not result in greater impacts on local air quality than other available options. 

In addition, methylal has a relatively lower Maximum Incremental Reactivity (MIR) (i.e., 0.94) relative to 

other pentane blowing agents (i.e., pentane [MIR = 1.31], isopentane [MIR = 1.45], and cyclopentane 

[MIR = 2.39]), which indicates methylal has a lower potential to produce ozone in the atmosphere 

compared to other commonly used blowing agents. As the calculated annual releases of methylal from 

these analyses are several orders of magnitude smaller than other anthropogenic sources of VOC 

emissions and are not significantly different than those for other available foam blowing agents, EPA 

believes that through the use of standard industry practices, the environmental impacts of these VOCs are 

not considered a significant concern.

5. POTENTIAL HEALTH EFFECTS

To assess potential health risks from exposure to the proposed substitute in foam blowing applications, 

EPA identified the relevant toxicity threshold values for comparison to modeled exposure concentrations 

for different scenarios. For the occupational exposure analysis, potential risks from chronic and acute 

worker exposure were evaluated by comparing exposure concentrations to available occupational 

exposure limits. Potential risks of chronic worker exposure were evaluated using workplace guidance 

 

2 The distribution of proposed foam end-uses is based on EPA’s Vintaging Model and may not necessarily represent 

the submitter’s intended market share for production of methylal.
 

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levels (WGLs). Risks from potential short-term consumer exposures were evaluated by comparing 

exposure concentrations to emergency guidance levels (EGLs). Table 4 lists the relevant toxicity limits

for methylal, and is followed by Table 5, which provides an explanation of each toxicity limit. EPA’s 

approach for identifying or developing these values is discussed in Chapter 3 of the Background 

Document. 

Table 4. Exposure Limits for Methylal

Component WGL (Long-term Exposure)

Ppm

EGL (Short-term Exposure)

ppm

Methylal 1,000a (8-hour OSHA PEL)

1,000b(8-hour ACGIH TLV-TWA)

1,250 (15-min ACGIH STEL)

aOSHA PEL available at: http://www.cdc.gov/niosh/npg/npgd0396.html

b ACGIH TLV-TWA available at: https://www.osha.gov/dts/chemicalsampling/data/CH_251500.html

Table 5. Explanation of Exposure Limit-Related Terminologya

Organization Definition

OSHA Occupational Safety and Health Administration

NIOSH National Institute for Occupational Safety and Health

ACGIH American Conference of Governmental Industrial Hygienists

Exposure Limit Definition 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 is 

within the Threshold Limit Value (TLV)–TWA, set by ACGIH. 

IDLH Immediately Dangerous to 

Life and Health

If exposed to this concentration, room occupants are expected to be 

able to escape the room within 30 minutes without experiencing 

escape-impairing or irreversible health effects.

Long-Term Exposure

PEL Permissible Exposure Limit This is an 8-hour time-weighted average exposure limit set by OSHA. 

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. 

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

According to the MSDS, exposure to methylal may be harmful by ocular or dermal absorption, inhalation, 

or ingestion. If methylal is inhaled, ingested, or absorbed through skin or eyes in large amounts, the 

affected person(s) should adhere to the first aid measures provided in the MSDS. In the case of ocular 

exposure, the MSDS for methylal recommends that person(s) should immediately flush the eyes with 

water and obtain emergency medical attention if pain, blinking, tears or redness persist. In the case of 

dermal exposure (including hair), the MSDS for methylal recommends that person(s) should immediately 

wash the affected area with soap and water and remove all contaminated clothing to avoid irritation. 

Medical attention should be sought if irritation develops or persists. The MSDS recommends personnel 

wear respiratory protection in the form of NIOSH and OSHA approved masks or respirators to avoid 

excessive methylal inhalation. If high concentrations of methylal are inhaled, person(s) should be 

immediately removed and exposed to fresh air. The MSDS recommends that if breathing is difficult, 

medical attention be sought. If methylal is ingested, the MSDS recommends that person(s) consult a 

physician immediately. If a large quantity of methylal was ingested, the MSDS recommends that 
 

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person(s) administer lukewarm water (only if person(s) are completely conscious and alert) in order to 

induce vomiting. EPA’s review of the human health impacts of this proposed substitute is contained in the 

public docket for this decision. These risks and procedures after exposure are similar for other common 

blowing agents.

EPA’s review of the human health impacts of this proposed substitute is contained in the public docket 

for this decision. These risks and procedures after exposure are similar for other common foam blowing 

agents. The potential health effects of methylal can be minimized by following the exposure guidelines 

and ventilation and PPE recommendations outlined in the MSDS for methylal and this risk screen. 

6. FLAMMABILITY ASSESSMENT

Methylal is flammable when its concentration in air is in the range of 2.2 percent to 19.9 percent by 

volume (22,000 ppm to 199,000 ppm) and is considered to be highly flammable (OSHA Class IB) at 

ambient temperatures and atmospheric pressure in both vapor and liquid form. Methylal has a flash point 

of -30.5 °C and in the presence of an ignition source (e.g., static electricity, a spark resulting from a 

closed door, a cigarette, or overheating), an explosion or a fire could occur if the concentration of 

methylal were to exceed the lower flammability limit (LFL) of 22,000 ppm (Holland Applied 

Technologies, Inc. 2014). 

[ ] When methylal is sold neat, used as the sole blowing agent, or combined with equally or more 

flammable blowing agents such as pentane,

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the flammability risk is higher. As a result, containers storing 

pure methylal should be properly labeled as highly flammable (OSHA Class IB) and grounded [ ] to 

prevent ignition from electrical sparks. Furthermore, all potential sources of ignition should be removed 

from the areas containing methylal and explosion proof equipment (e.g., pump, agitator, light, 

heating/cooling) [ ] should be installed in accordance with the MSDS.

EPA recommends personnel follow the proper precautions specified in the substitute’s MSDS. By 

removing any sources of ignition from areas containing methylal, ensuring warning and flammable labels 

are affixed to all methylal containers, and by installing recommended equipment and adhering to the other 

precautions listed in the proposed substitute’s MSDS, it is unlikely that methylal will pose a significant 

flammability risk for use in foam blowing.

7. OCCUPATIONAL EXPOSURE ASSESSMENT

This section presents estimates of potential occupational exposures to methylal, which is anticipated to 

occur during manufacture of blown foam. To ensure manufacture and application of methylal for the 

proposed foam blowing end-uses do not present a risk to workers, occupational exposures were derived 

from personal and area sampling data provided by the submitter.

According to the submitter, personnel monitoring data during production of various foam end-uses has 

 

3 Methylal is less flammable than commonly used foam blowing agents such as methyl formate, n-pentane, and 

isopentane, which are all designated Class I flammable liquids. In addition to a lower flammability risk, methylal 

also has a lower risk of detonation or explosion compared to pentane. Methylal’s heat of combustion (i.e. 6.1 kcal/g) 

is almost half of pentane’s (i.e. 11.5 kcal/g), resulting in a lower likelihood of explosion in the presence of ignition 

sources (Holland Applied Technologies, 2014). 
 

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shown that exposure to methylal would be significantly less than the TLV (i.e., 1,000 ppm). [ ]

8. GENERAL POPULATION EXPOSURE ASSESSMENT

Methylal is not expected to adversely impact human health in the general population during manufacture 

or end-use blowing agent formulations. Releases of methylal into the environment are not expected, 

because manufacture and foam blowing agent mixing are performed in closed systems and air emissions 

would be trapped within the vessel or equipment in use. Furthermore, [ ] are formulated in specialized 

plants. If any significant release of methylal were to occur, emissions would likely be trapped in plant 

scrubbers which collect and prevent the release of the proposed substitute to the atmosphere. Therefore, 

EPA believes direct exposure to consumers is not a concern beyond the general population exposure 

scenario discussed below.

8.1 Chronic Exposure to Methylal during Lifetime Foam-Blowing Agent Releases 

There is the potential for chronic general population exposures to foam-blowing agents during the lifetime 

of the foam in which they are used, because these agents can slowly leak from the foam over time. As a 

result, in locations where persons are regularly present for extended periods, such as a home or apartment, 

the persons could be exposed to very low levels of methylal over time. Based on the foam blowing enduses proposed for methylal, the maximum annual rate of release of methylal (i.e., after manufacture and 

before disposal) is anticipated to be 2.5% (see Table 3), resulting in very minimal exposure 

concentrations for the general population. Due to the low toxicity of methylal and minimal expected 

release, EPA believes that such exposures do not pose a significant toxicity risk, and thus, methylal is not 

expected to cause a significant impact on human health in the general population when used as a foam 

blowing agent in the proposed end-uses.4

Because the proper safety and disposal precautions, as listed in this section, are followed, methylal is not 

expected to cause a significant threat to the environment and human health in the general population when 

manufactured or used for rigid polyurethane appliance foam: rigid polyurethane commercial refrigeration 

and sandwich panels; rigid polyurethane & polyisocyanurate laminate boardstock; rigid polyurethane 

slabstock; flexible polyurethane; and integral skin polyurethane end-uses.

 

4 Additional information would be needed to evaluate the risks of blends of methylal and other foam blowing agents 

for use in certain rigid cell residential foams. As stated in the final rule, 59 FR 13044, “[EPA] has determined that 

because of the potential for formation and emission of decomposition products in rigid closed cell foams, 

notification and review under SNAP is required for blends of chemical alternatives in foam end-uses that encompass 

residential products where chronic consumer exposure could occur. These end-uses are: polyurethane rigid 

laminated boardstock, polystyrene extruded boardstock and billet foams, phenolic foams, and polyolefin foams.”
 

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9. REFERENCES

Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. 

Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland. 2007. Changes in 

Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science 

Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel 

on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and 

H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Holland Applied Technologies, Inc. 2014. SNAP Submission. 2014. Significant New Alternatives Policy 

Program Submission to the United States Environmental Protection Agency, April 2014.

U.S. EPA 1994. Significant New Alternatives Policy Technical Background Document: Risk Screen on 

the Use of Substitutes for Class I Ozone-depleting Substances: Foam-Blowing Agents. U.S. 

Environmental Protection Agency, March 1994.

U.S. EPA 2014. Volatile Organic Compounds – National Emissions Inventory (NEI) Air Pollutant 

Emissions Trends Data and Estimation Procedures. Last updated 17 July 2014. Accessed 18=7 

September 2014. Available at <http://www.epa.gov/ttnchie1/trends/>.

WMO (World Meteorological Organization), 2011. Scientific Assessment of Ozone Depletion: 2010, 

Global Ozone Research and Monitoring Project—Report No. 52, 516 pp., Geneva, Switzerland, 2011.