Air samples show an industrial atmosphere for an 8-hour shift to contain Methyl

Question

Air samples show an industrial atmosphere for an 8-hour shift to contain Methyl acetate. The following concentrations were observed. (PEL for Methyl acetate is 200mg/m3) Assuming no other contaminants are present what is the TWA? Does the exposure exceed the PEL? (5 points) Time Methyl acetate 8:00-9:00 185mg/m3 9:00-11:15 195mg/m3 11:15-2:00 205mg/m3 2:00-3:30 205mg/m3 3:30-4:00 193mg/m3 Question 47 options: TWA is 1591.5 and the PEL has been exceeded TWA is 205 and the PEL has not been exceeded TWA is 205 and the PEL has been exceeded TWA is 198.94 and the PEL has not been exceeded

Explanation / Answer

TWA = 1*185 + 2.25*195 + 2.75*205 + 1.5*205 + 0.5*193

= 185 + 438.75 + 563.75 +307.5 + 96.5

= 1591.5

Exposure = 1591.5 / (1+ 2.25 + 2.75 + 1.5 +0.5)

= 1591.5 / 8 = 198.9375 mg/m3

now 198.9375 mg/m3 < 200 mg/m3

so, exposure doesn't exceed the PEL.

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