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

Disable ads (and more) with a membership for a one time $4.99 payment

Prepare for the HAZWOPER 8 Hour Refresher Test with our comprehensive materials. Study with flashcards, multiple-choice questions, and get detailed explanations on each topic. Ensure you're ready for your certification update!

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