Please solve the following problem, indicating your response on a Word document

Question

Please solve the following problem, indicating your response on a Word document and submitting the document via File Upload.

Using the following formula, solve the problem below, and show your work.

TWA = CaTa + CbTb + ... + CnTn
8

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?

TWA = Time-Weighted Average 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"

Explanation / Answer

Using the following formula, solve the problem below, and show your work.

TWA = CaTa + CbTb + ... + CnTn / 8

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?

Answer

In the given problem

Ca = 500 ppm & Ta = 1 hour

Cb = 100 ppm & Tb = 4 hour

Cc = 225 ppm & Tc = 3 hour

Using the given relation

TWA = (Ca * Ta + Cb * Tb + Cc * Tc ) / 8

TWA = (500 * 1 + 100 * 4 + 225 *3) / 8

TWA = (500 + 400 + 675 ) / 8

TWA = (1575) / 8 = 196.875 ppm

TWA = 196.875 ppm (Answer)

The Occupational Safety and Health Administration has established a Permissible Exposure Limit of 200 parts per million (ppm)

Since the TWA (196.875 ppm) is just below the Permissible Exposure Limit of 200 ppm the worker is not over exposed to toluene. However, since the exposure as per calculated TWA is very close to PEL , it is advisable that control measures like wearing appropriate respirators should be followed so that the worker is not over exposed beyond PEL.

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