### MEMORA **NDUM**

To: Margaret Sheppard, U.S. EPA CC: Bella Maranion, Melissa Fiffer, and Carolyn Hayek, U.S. EPA From: Rebecca Ferenchiak, Jenny Tanphanich, Neha Mukhi, and Mark Wagner , ICF International Date: August 1 , 2011 Re: Additional End -Use Modelin g for Household Refrigerators and Freezers

(EPA Contract Number EP - W - 10 - 0 31 Task Order 005 , Task 01 ) ICF has reviewed the public comment submitted by Honeywell (EPA - HQ - OAR - 2009 - 0286 - 0170.1) in response to EPA’s proposed SNAP ruling which approves the use of hydrocarbon refrigerants in refrigerators ([ EPA - HQ - OAR - 2009 - 0286; FRL - 9147 - 9] RIN 2060 - AP54) . In the comment, Honeywell specifically notes that in EPA’s risk screen for isobutane in household refrigerators and freezers , the flammability risk for isobutane is underestimated. To support this notion, Honeywell performed leak testing of an isobutane refrigerator and provided the test results in their comment. In this memorandum, ICF examines the impact of using more conservative assumptions in the flammabil ity assessment for isobutane and R- 441A to determine whether a flammability risk exists. Please contact Mark Wagner at 202 - 862 - 1155 with any questions or comments.- 2 -



### Background In Comment EPA - HQ - OAR - 2009 - 0286 - 0170.1 ( FRL - 9147 - 9 , RI N 2060 - AP54 ) , Honeywell s tates that EPA underestimated the flammability risks associated with the use of isobutane as a refrigerant in household refrigerators and freezers. Consequently, ICF, at the request of EPA, has revisited the end -use modeling performed for both substitutes proposed for use in household refrigeration , isobutane and R441A , and performed an additional flammability analysis and threshold analysis . 

### Discussion of End **- Use Scenarios Modeled**  ICF reviewed the a ssumptions made in the original risk screens for iso b ut ane and R - 441A ( formerly known as HCR - 188C1) , dated May 22, 2009 and November 6, 2009 respectively, to determine whether they were sufficiently conservative to represent a rea sonable worst - case scenario. The assumptions used in the original risk screens f or worst - case scenario modeling are summarized in Table 1. **Table 1. Worst -**  **Case Scenario Model Assumptions in Risk Screen**  **Parameter Risk Screen Assumption**  **s :**  **Isobutane Risk Screen Assumption**  **s :**  **R -**  **441A** Appliance Household Refrigerator Household Refrigerat or Room Household Kitchen Household Kitchen Charge size (g) 50 40 Percentage of Charge Leaked 100% 100% Length of release (minutes) 1 1 Room size (volume - m 3 ) 18 18 Room ventilation (air changes per hour) 2.5 2.5 Horizontal stratification 95% in b ottom 0.4 m (~16 in) of room 95% in bottom 0.4 m (~16 in) of room Charge Size The charge sizes originally modeled for isobutane and R - 441A were 50g and 40g, respectively. These values were chosen for modeling based on statements in the SNAP submissions for these substitutes that indicated the intended charge sizes to be used in appliances . There is the potential to be more conservative in the setting of this parameter for additional flammability analysis, since EPA’s proposed rule allows a household r efrigerator to have a charge size of up to 57g. T he proposed rule also effectively require s that the charge size be consistent with the standard UL 250 Supplement SA, which calls for a maximum leak amount of 50 grams for refrigerants with flammability limits and a heat of combustion greater than 19,000 kJ/kg, such as isobutane or R- 441A . However, the test to determine leak amounts is not documented in the UL 250 Standard and could potentially be administered incorrectly. As a result, in the additional flammability analysis (described in the following section) ICF uses a leak amount of 57g as a more conservative assumption for purposes of additional flammability analysis. Room Size In the original risk screen analysis, a kitchen with a floor area of 7.4 m2 and a ceiling height of 2.4 m was assumed ( EPA, 1994) . This is equivalent to a volume of 18 m3

. Although very l imited data are available regarding the distribution of kitchen volume s in the United States , an analysis by Murray (1997) which aggregated dat a from over 60 different projects report ed the minimum kitchen volume encountered as 31 m3

. 1 Further, only one percent of houses sampled had a kitchen smaller than 53 m3

. Therefore, ICF does

1 Murray (1997) uses data from the Brookhaven National Laboratory PFT database. Data regarding kitchen volumes- 3 -

not believe there is a need to be more conservative in the setting of this parameter for the purpose of the additional flammability analysis. Room ventilation The range of potential flow rates for a residential kitchen is believed to be 2.5 to 4.5 air changes per hour ( ACH ) (Sheldon 1989). The more conservative rate of 2. 5 ACH was used in the analyses, and ICF does not believe there is a need to be more conservative in the setting of this parameter for the purpose of additional flammability analysis. Horizontal Stratification In the original risk screen, it was assumed that h orizontal stratification will occur since both isobutane and R - 441A are denser than air and as a result, settle in higher concentrations closer to the ground. In order to simulate the horizontal concentration gradient that will occur because of the weight differential between the refrigerant and air, ICF assumed that 95 percent of the leaked refrigerant mixes evenly into the bottom 0.4 meter s of the room, and the remainder of the refrigerant mixes evenly in the remaining volume (Kataoka 1999). There is the potential to be more conservative in the setting of this parameter for additional flammability analysis, since the release point for a refrigerant may vary with the type of appliance in use. To capture the scenario of a bottom- freezer refrig erator, which would likely have the lowest release point, this flammability analysis will assume that 95 percent of the leaked refrigerant mixes evenly into the bottom 0.2 2 meter s (~ 9 inches) 2 of the room, and the remainder of the refrigerant mixes evenly in the remaining volume . 

### Additional Flammability Analysis and Results Table 2 details the assumptions that will be used for the additional analys es of flammability risks associated with the use of isobutane or R- 441A in the household refrigeration end-us e. **Table 2. Assumptions for**  **the Additional**  **Worst -**  **Case Scenario Flammability Analysis** 

**Parameter New Assumption**  Refrigeration Unit Household Refrigerator Room Household Kitchen Leak Amount (g) 57* Length of release (minutes) 1 Room size (volume - m 3 ) 18 Room ventilation (air changes per hour) 2.5 Horizontal stratification 95% in bottom 0.2 2 m (~9 in) of room* *More conservative than the assum ption used in the original risk screen s . Based on the re - analysis, a ssumptions are the same as those modele d in the original risk screen , with the exception of the charge size (increased to 57g) and the stratification level assumption s (95% of the were only available for the Lo s Angeles area and the kitchen volumes are for a “kitchen zone” which may include associated areas, such as utility rooms, dining room s, living rooms, and family room. The inclusion of these other spaces in the “kitchen zone” volume is realistic, as the presence of adjoining rooms would increase the volume into which the refrigerant could leak. 2 This value is consistent with the locati on for a potential leak from the condenser - com pressor department for a bottom freezer depicted in comment EPA - HQ - OAR- 2009 - 0286 - 0170.1.- 4 -

refrigerant will settle into the bottom 0.2 2 m [ ~9 in .] of the room). The results of this secondary analysis for i so butane and R- 441A compared to the results of the original analysis are shown in Table 3.

**Table 3. Maximum Concentrations in Lower Compartment of Kitchen Proposed Substitute**  **Maximim Concentration: Original Assumptions**  **a (ppm)**  **Maximum Concentration: Cons**  **ervative Assumptions b**  **(ppm)** Isobutane c 6,647 13,778 R - 441Ad 6,236 16, 153 a See Table 1 b See Table 2 c Isobutane LFL is 18,000 ppm d R - 441A LFL is 16,800 ppm Although the concentrations in the lower compartment of the kitchen increased for both isobutane and R441A after using more conservative charge size and stratification assumptions, the maximum concentrations remained below the LFL for both compounds. The maximum concentration for R- 441A is within 95% of the LFL (16,800 ppm); however, i t is unlikel y that concentrations would reach these levels using either refrigerant in a real - life leak situation, due to the conservative nature of the assumptions. As noted previously, it is unlikely that a kitchen size would be 18 m3 and that the entire 57 gram charge would leak . 

### Threshold Analysis and Results A threshold analysis was also performed to assess the impact of differences in room volume and leak amount and to determine the needed parameter v alu es for leaked concentrations to reach the LFL for isobutane and R- 441A. One of the two assumptions in the revised flammability analysis ( i.e., room size and leak amount) was changed while the other assumptions remain ed constant (see Table 2) to determine the value at which concentrations in the lower compartment of the kitchen would reach the LFL for isobutane and R- 441A . The results of the threshold analysis are shown in Table 4 .

**Table 4**  **. Room volumes and leak amounts necessary to reach**  **LF L**  **Refrigerant** a,b **Room Size (Volume) Leak Amount**  Isobutane 18 m 3 **75 g** Isobutane **13.8 m 3**  57g R - 441A 18 m 3 **59 g** R - 441A **17.3 m 3**  57g a Lower Flammability Limit of isobutane is equal to 18,000 ppm . b Lower Flammability Limit of R -441A is equal to 1 6, 800 ppm .. Assuming a room volume of 18 m3 , the charge sizes required for the concentration in the lower compartment of the kitchen to reach the LFL for isobutane and R- 441A were 75 grams and 59 grams, respectively. Based on the proposed SNAP ruling, the charge sizes required to reach the LFL would not be allowed for household refrigerators. Further, although a charge size of 59 grams for R- 441A is close to the allowable 57 gram charge size, the UL Standard 250 requires that if a charge size of 57 grams is used, engineering controls must be in place to ensure that only 50 grams (or approximately 88%) can leak from the system. If the charge size of 57 grams was held constant, kitchen volumes of 13.8 m3 (487 ft 3 ) and 17.3 m3 (611 ft 3 ) would be necessary for isobutane and R- 441A concentrations , respectively, in the lower compartment of the kitchen to reach the LFL. Both threshold kitchen volumes are lower than the original assumed kitchen volume of 18 m3 . However, as noted previously, it is highly unlikely that a kitchen would exist at- 5 -

such small volumes

—only one percent of houses sampl ed in more than 60 different projects had a kitchen smaller than 53 m3 (Murray 1997). 

### Additional Discussion Depending on the mixing conditions, it is still possible that in certain locations at floor - level , or in restricted areas such as a space between a refrigerator and a wall , the concentrations of isobutane or R441A could reach their LFLs for a few minutes , posing a threat in the presence of a spark . However, the annual probability of an external leak occurring over the course of minutes and an igniti on source being present simultaneously is approximately 5.0 x 10 - 7 (i.e., 0.5 in one million) ( A.D. Little 1991). T o avoid the risk of fire and explosion , it is recommended that refrigerators containing isobutane or R441A not be installed in small, poorly ventilated spaces such as very small enclosed ‘galley’ kitchens 3 or storage closets (especially as other equipment or appliances in the space would reduce the effective volume of the room). F or full - sized kitchens and for kitchens with typical ventilat ion levels, the risk of fire and explosion is minimal.

3 Enclosed galley kitchens are kitchens that are not open to the r est of the dwelling, generally have two (or occasionall y three) sides, and have a pass way or doorway entrance, but no door .- 6 -



### References A.D. Little 1991. Risk Assessment of Flammable Refrigerants for Use in Home Appliances. Arthur D. Little, Inc. for EPA, Climate Change Division. September 10, 1991. Docket item E PA - HQ OAR - 2009 - 0286 - 0023. 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. EPA 2009. Risk Screen on Substitutes for CFC - 12 in Household Refrigerators and Freezers: Isobutane. Stratospheric Protection Division. Prepared by ICF International. March 2009. Honeywell 2010. Honeywell International, Inc. Comment on EPA Proposed Rule. Protection of Stratospheric Ozone: Listing of Substitutes for Ozone - Depleting Substances - Hydrocarbon Refrigerants. EPA - HQ - OAR - 2009 - 0286; FRL - 9147 - 9. July, 2010. Kataoka. 1999. “Allowable Charge Limit of Flammable Refrigerants and Ventilation Requirements.” Draft Proposal. O. Kataoka/Daikin/Japan, June, 1999. Murray, D.M. 1997. “Residential House and Zone Volumes in the United States: Empirical and Estimated Parametric Distributions.” Risk Analysis . 17(4): 439 - 446. Sheldon, L.S., et al . 1989. "An Investigation of Infiltration and Indoor Air Quality." New York State Energy Research & Development Authority, Report 90 - 11. UL. 2000. UL 250: Standard for Household Refrigerators and Freezers. Underwriters Laboratory.