You are an industrial hygienist conducting personal sampling on a worker who is overseeing a production process involving use of acetone (Note: The Occupational Safety and Health Administration has established a Permissible Exposure Limit of 1000 parts per million (ppm) of acetone). You are able to measure the following exposures:
700 ppm for 3 hours
1300 ppm for 2 hours
900 ppm for 3 hours
What is the calculated TWA? What would you tell plant management in terms of exposure to acetone and compliance with the PEL?