Using the following formula, solve the problem below, and show your work.
TWA = CaTa + CbTb + … + CnTn
|Ca||=||Concentration of contaminant during the sampling period “a“|
|Ta||=||Time of sampling period “a“|
|Cb||=||Concentration of contaminant during the sampling period “b”|
|Tb||=||Time of sampling period “b“|
|Cn||=||Concentration of contaminant during the sampling period “n“, where “n” is the last of a series of contaminants|
|Tn||=||Time of sampling period “n“|
Note: All concentrations are in parts contaminant per million parts of air or milligrams of contaminant per cubic meter of air.
Air Sampling Problem: You are an industrial hygienist that is conducting personal sampling on a worker who is overseeing a production process involving use of toluene (Note: The Occupational Safety and Health Administration has established a Permissible Exposure Limit of 200 parts per million (ppm)). You are able to measure the following exposures:
500 ppm for 1 hour
100 ppm for 4 hours
225 ppm for 3 hours
What is the calculated TWA? What would you tell plant management in terms of exposure to toluene and compliance with the PEL?