Predicting Exposures - Part II

Location – (Web PDC)

Instructions regarding how to log onto the web PDC and the conference call phone number, as well as handouts, will emailed to the registered participants the week before the PDC.


Paul Hewett Ph.D. CIH

Course Description

This web PDC introduces the participant to several modeling topics: decreasing emission Well Mixed Room (WMR) models, estimating short-term and peak exposures, predicting generation rates using several published algorithms, comparison of control options, and use WMR models to predict potential exposures after a spill or upset condition.  Modeling software (Windows only) will be provided that is capable of Monte Carlo Simulations (i.e., the prediction of an exposure profile).  This PDC will concentrate on the practical application of WMR models to several exposure scenarios.  Participants are encouraged to bring modeling examples.

The PDC will last 3.0 hours, with an additional 30 minutes for Q&A.  Each participant will receive a certificate confirming participation in the PDC.

Learning Objectives:

Upon completion, participants will be familiar with the following topics:

  • Selection of an appropriate WMR, Decreasing Emission model.
  • Using a WMR model to predict short-term (i.e., 15-minute) and peak exposures.
  • Selection and use of appropriate generation rate prediction algorithm.
  • Estimating the potential benefit of using a local ventilation control.
  • Predicting vapor concentrations immediately after a workplace spill.


  • Participation in the web PDC “Predicting Exposures – Part I”
  • Familiarity with the AIHA Exposure Assessment and Management Model (see the AIHA monograph “A Strategy for Assessing and Managing Occupational Exposures”, 4rd Edition (2015)

Rcommended Reading

  • Hewett, P. (2017): Easy Modeling – Forecasting Occupational Exposures Using “Well Mixed Room” Models. Synergist (April) 24-29.
  • Hewett, P. and Ganser, G.H. (2017): Models for Nearly Every Occasion: Part III – One Box Decreasing Emission Models. Journal of Occupational and Environmental Hygiene 14:907-918.
  • Ganser, G.H. and Hewett, P. (2017): Models for Nearly Every Occasion: Part IV – Two Box Decreasing Emission Models. Journal of Occupational and Environmental Hygiene 14:919-930.
  • Nicas, M. and Armstrong, T.W. (2015): Appendix I – Estimating Airborne Exposure by Mathematical Modeling. In A Strategy for Assessing and Managing Occupational Exposures. (editors: Jahn, S.D., Bullock, W.H., and Ignacio, J.S.) American Industrial Hygiene Association, Fairfax, VA.

Presentation List

  • Introduction to WMR Decreasing Emission models (used for evaporation scenarios)
  • Introduction to Generation Rate Prediction Algorithms
  • Comparing Control Options
  • WMR Modeling and Workplace Spills
  • Discussion of WMR Modeling Research Needs
  • Stump the Instructor: Evaluation of Student Exposure Scenarios
  • Q&A


See Registration page.

Cancellation Policy

See Registration page.

Read these notes before you sign up:

NOTE: The registration and participation policy for each Web PDC is the same as for a fixed location or on-site PDC. Registration is per participant, not per viewing site. Each participant must register.  Only those registered should view and participant in this web PDC.

NOTE: The email address submitted at the time of payment will be used for all email communications and for logging onto the web PDC.

NOTE: This web PDC will presented using GoToMeeting. GoToMeeting must be installed on your computer. To install (usually takes less than two minutes), click on the GoToMeeting link above, scroll to the bottom of the page, and click on the link “Download GoToMeeting (for customers)”. If you do not have administrative privileges for your computer have your IT person install the GoToMeeting software at least the day before the web PDC.

NOTE: The conference call number will not be toll free. You will be responsible for any long distance phone charges if you do not have an unlimited long distance account. However, you may also connect using your computer speakers and microphone or headset (VoIP).

NOTE: See the “Prerequisites” below for software and freeware that will be helpful when taking this web PDC. To download and install the program(s) you must first be a registered member of