Submarine Exposure Guidance Levels for Selected Hydrofluorocarbons: HFC-236fa, HFC-23,and HFC-404a (2000)
Chapter: Calculations Used to Determine EEGLs and CEGL for HFC-404a
TABLE 4-5 Submarine Exposure Guidance Levels for HFC-404a Components
where the value of 24.45 is the molar volume of air in liters at a pressure of 760 mm Hg and a temperature of 25°C.
The 1-hr EEGL, 24-hr EEGL, and 90-day CEGL for HFC-404a were calculated to be 12,900 ppm, 4,300 ppm, and 800 ppm, respectively. The Navy proposes to use lower guidance levels of 2,000 ppm for the 1-hr EEGL, 1,000 ppm for the 24-hr EEGL, and 100 ppm for the 90-day CEGL, which the subcommittee concludes are conservative values that are protective of submariner health.
CALCULATIONS
Calculations Used to Determine EEGLs and CEGL for HFC-404a
HFC-404a contains by weight: 52% HFC-143a, 44% HFC-125, and 4% HFC-134a
The equation below was used to calculate the 1-hr and 24-hr EEGLs and 90-
day CEGL for the mixture HFC-404a; f is the fraction of each component of the mixture and EGL is the component's corresponding exposure guidance level (which must be expressed in terms of milligrams per cubic meter):
Using the values in Table 4-5, the EGLs for HFC-404a were calculated as follows:
1-hr EEGL:
Of the mixture,
52% or 52,075 mg/m3 × 0.52 = 27,079 mg/m3 is HFC-143a
44% or 52,075 mg/m3 × 0.44 = 22,913 mg/m3 is HFC-125
4% or 52,075 mg/m3 × 0.04 = 2,083 mg/m3 is HFC-134a.
These values can be converted to parts per million as follows:
HFC-143a: 27,079 mg/m3 × 0.29 = 7,853 ppm
HFC-125: 22,913 mg/m3 × 0.20 = 4,583 ppm
HFC-134a: 2,083 mg/m3 × 0.24 =500 ppm.
The 1-hr EEGL of HFC-404a = 7,853 + 4,583 + 500 ≈ 12,900 ppm.
24-hr EEGL:
Of the mixture,
52% or 17,341 mg/m3 × 0.52 = 9,017 mg/m3 is HFC-143a
44% or 17,341 mg/m3 × 0.44 = 7,630 mg/m3 is HFC-125
4% or 17,341 mg/m3 × 0.04 = 694 mg/m3 is HFC-134a.
