HAZWOPER 8 Hour Refresher Training Practice Test 2025 - Free Hazardous Waste Operations Practice Questions and Study Guide

Question: 1 / 445

You are exposed to acetone at a concentration of 80 ppm for 6 hours and 20 ppm for 2 hours. What is the TWA?

8 ppm

20 ppm

100 ppm

65 ppm

To determine the Time-Weighted Average (TWA) exposure concentration over a specified time period, the formula used combines the different concentrations and the duration of exposure to each concentration.

In this case, the first exposure is to acetone at 80 ppm for 6 hours and the second exposure is to 20 ppm for 2 hours. To find the TWA, the total exposure in ppm-hours needs to be calculated for both periods.

First, we calculate the exposure for each concentration:

For the first exposure:

- 80 ppm for 6 hours = 80 ppm * 6 hours = 480 ppm-hours.

For the second exposure:

- 20 ppm for 2 hours = 20 ppm * 2 hours = 40 ppm-hours.

Next, we add the total exposure from both periods:

- Total exposure = 480 ppm-hours + 40 ppm-hours = 520 ppm-hours.

Then, we consider the total time of exposure, which is 6 hours + 2 hours = 8 hours.

Finally, we calculate the TWA:

- TWA = Total exposure (ppm-hours) / Total time (hours) = 520 ppm-hours / 8 hours = 65 ppm.

This value, 65

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