November 30, 2007

Mr. Richard Maruya

A.S. Trust & Holdings

PPP 469 Box 10000

Saipan, MP

Dear Mr. Maruya:

Following a review of the calculations contained within Assessment of End-Use Occupational and 

Residential Occupant Exposures to HCR-188C, A Safe Alternative Hydrocarbon Refrigerant for 

White Goods Systems, (May 2007) and three subsequent amendments prepared in July and 

November 2007, Alaska Industrial Hygiene Services (AIHS) has confirmed an error in the 

calculations associated with occupational exposures to HCR-188C. The calculation error is related 

to the size of the “box” used for calculating occupational exposures to HCR-188C during hose 

connection/disconnection cycles.

In the original risk assessment document and the three amendments, a value of 9 cubic feet (0.26 

cubic meters) was used for the calculations. The correct value that should have been used is 27 

cubic feet (0.7646 cubic meters). The “box” was described as being 3 feet by 3 feet by 3 feet

(equivalent to 27 cubic feet), but when the calculations were performed, the incorrect value of 9 

cubic feet was used. The calculations affected by this error were used to determine peak and 

time-weighted average exposures expressed in parts per million (ppm) by volume for a 

refrigeration technician performing product servicing activities. The calculated peak exposure 

value was also used to evaluate flammability concerns expressed as a percentage of the lower 

flammability limit (LFL) of HCR-188C.

AIHS recalculated the potential exposures contained in the original risk assessment and three 

amendments. The recalculated values are presented in the tables below. As can be seen by the 

data, the corrected exposure values are lower than the original values as a result of the calculation 

error.

Table 1: Corrected Values for May 2007 Assessment – Refrigerator

Volume of HCR-188C

(0.2% of Charge Rate)

Peak Exposure 

(ppm)

8-Hour TWA

Exposure (ppm)

% of the LFL

0.0566 grams Original 112.4 Original 1.9 Original 0.5

Corrected 36.7 Corrected 0.6 Corrected 0.2

0.0792 grams Original 157.2 Original 2.6 Original 0.8

Corrected 51.4 Corrected 0.9 Corrected 0.3
Mr. Richard Maruya

A.S. Trust & Holdings

November 30, 2007

Page 2 of 2

Table 2: Corrected Values for July 2007 Amendment – Window Air Conditioner and Stand

Alone Freezer

Volume of HCR-188C

(0.2% of Charge Rate)

Peak Exposure 

(ppm)

8-Hour TWA

Exposure (ppm)

% of the LFL

0.2495 grams (window air Original 495.3 Original 8.3 Original 2.5

conditioner) Corrected 162.0 Corrected 2.7 Corrected 0.8

0.2438 grams (window air Original 484.0 Original 8.1 Original 2.4

conditioner) Corrected 158.3 Corrected 2.6 Corrected 0.8

0.08 grams (freezer) Original 158.8 Original 2.7 Original 0.8

Corrected 51.9 Corrected 0.9 Corrected 0.3

Table 3: Corrected Values for November 2007 Amendment – Window Air Conditioner

Volume of HCR-188C

(0.2% of Charge Rate)

Peak Exposure 

(ppm)

8-Hour TWA

Exposure (ppm)

% of the LFL

0.4876 grams Original 968.1 Original 16.1 Original 4.8

Corrected 316.5 Corrected 5.3 Corrected 1.6

Table 4: Corrected Values for November 2007 Amendment – Stand Alone Freezer

Volume of HCR-188C

(0.2% of Charge Rate)

Peak Exposure 

(ppm)

8-Hour TWA

Exposure (ppm)

% of the LFL

0.0836 grams Original 166.0 Original 2.8 Original 0.8

Corrected 54.3 Corrected 0.9 Corrected 0.3

0.1062 grams Original 211.0 Original 3.5 Original 1.1

Corrected 68.9 Corrected 1.1 Corrected 0.3

If you have any questions or require additional information related to this letter, please don’t

hesitate to contact me at your earliest convenience by telephone at 907-336-2447 or by email at

dburks@acsalaska.net.

Thank you.

Sincerely,

Darren D. Burks, CIH, CSP