You are conducting personal air sampling for methyl chloride exposure in a furniture refinishing facility. The employee you are sampling works an 8. 5-hour shift. This includes 0.5 hours for lunch. The employee performs two 15-minute cleaning tasks with potential higher exposures to methyl chloride at the start of the shift and after lunch. The remaining work times are spent performing normal production tasks. In, the employee comes in and does the 15-minute cleaning task, then works for 225 minutes, takes a lunch break (0.5 hrs.) with no exposure, and repeats the morning tasks in the afternoon. You decide to take four samples that represent the
different methyl chloride exposures of the employee during the work shift. The sampling results are reported below.
Sample 1 and 3 are the STEL samples, and samples 2 and 4 are the 225-minute samples. Calculate the 8 hour-TWA exposure to methyl chloride. Compare all sample results and the 8 hour-TWA exposure to the TLV for methyl chloride.
Use the ACGIH TLV-TWA and TLV-STEL as comparisons. What is your recommendation?
Sample 1 = 96.9 ppm methyl chloride for 15-minute sample
Sample 2 = 8.6 ppm methyl chloride for 225-minute sample
Sample 3 = 145.2 ppm methyl chloride for 15-minute sample
Sample 4 = 12.9 ppm methyl chloride for 225-minute sample
ACGIH TLV for methyl chloride:
TLV-TWA = 50 ppm
TLV-STEL = 100 ppm