Mixtures present some additional complexities compared to assessment of exposure from pure compounds. For many mixture, one particular component is the main concern. If so, there are ways to undertake that components exposure potential. Do you remember Raoult’s Law from general chemistry? It is pretty simple because it assumes “ideal” behavior. Then, the partial vapor pressure of a mixture component is equal to its pure substance vapor pressure time the MOLE FRACTION of the component in the mixture. For further explanation, here is a link to a short You Tube video.
Unfortunately, the “ideal” behavior assumption has so many exceptions that it often leads to significant errors either high or low. So, what can we do? Look to ACTIVITY COEFFICIENTS. These add some complexity but can greatly improve the accuracy of partial pressure predictions. The most used is probably a “UNIFAC” activity. See this site’s page Tutorials, Theory, Parameter values for a PDF copy of a PowerPoint slide set. Look at Slides 10 to 15 for more information. Also, see my esteemed friend Mike Jayjock’s Risk Assessment Blog, http://jayjock-associates.blogspot.com/2013/09/getting-activity-coefficients-for.html or http:// https://jayjock-associates.blogspot.com/2013/09/gifts-from-netherlands-more-unifac-and.html for more information. Unfortunately, the one UNIFAC calculator is no longer available at the link Mike provides. I decided to provide a link to a copy in a Dropbox folder.
https://www.dropbox.com/t/sOT9P5SDv3Cjr3VI
This older but reliable calculator has become hard to find. Write to me twa8hr@gmail.com
for a copy, or download from the Dropbox link above.