Skip Ribbon Commands
Skip to main content

PDC 15 - Forecasting Exposures Using the New "Well​​ Mixed Room" Models

Enterprise Risk Management and Risk Assessment​ Track

Intermediate | Credits: 8 CM Credit Hours 

Wednesday, November 1 | 8:00 AM – 5:00 p.m. | Limit 40


The new one and two-box "Well Mixed Room" (WMR) models (JOEH, Jan 2017) will be introduced, along with a systematic approach to calibrating a WMR model.  Free student software (Windows only) will be provided that allows a student to quickly select and apply a WMR model.  The software is capable of Monte Carlo Simulations, where any or all of the model variables are also modeled (using one of several statistical distributions), resulting in the prediction of an exposure profile, rather than the prediction of a single value.

Students are encouraged to bring modeling examples and to try to stump the instructors (good luck!).  The course ends in a modeling melee where the students compete to correctly model a series of exposure scenarios.  This PDC course will be light on theory and heavy on the practical application of WMR models.  

A word of caution!  These "new" models have yet to be validated in peer-reviewed literature and the software has yet to be thoroughly tested by anyone other than the instructors.  Nonetheless, students will learn the basics of modeling and will have good time doing it.

*Registration includes boxed lunch.


Participants should have a background in IH exposure assessment and an understanding of IH statistics.

Learning Aids

A Windows laptop is recommended, along with a computer mouse, as it makes using the software so much easier and faster. A hand calculator will be useful, but is not required.

Value Added​​

Each student will receive free student modeling software, checklists for collecting exposure determinant information, and the skills to add probabilistic modeling methods to their exposure assessment toolbox.

Course Outline

  • Introduction to the New WMR models
  • Model Calibration
  • Deterministic and Probabilistic Modeling
  • Use of the Modeling Software
  • Group Workshop
  • Evaluation of Student Exposure Scenarios
  • Modeling Melee - Group Competition

Learning Outcomes

Upon completion, participants will be able to:

  • Select an appropriate “Well Mixed Room” model.
  • Know when to use constant emission vs. decreasing emission models.
  • Calibrate a model using field measurements and/or default values.
  • Use the student software to describe a job as a series of modeled tasks.
  • Predict an entire exposure profile using Monte Carlo Simulation.

Transfer of Knowledge

Instructors will evaluate participants’ understanding of the materials presented based on:

  • Group activities
  • Workshops



Name and Bio

​Paul Hewett, PhD, CIH, Founder & President, Exposure Assessment Solutions, Inc., Morgantown, WV.

Paul Hewett, PhD, CIH is the founder and President of Exposure Assessment Solutions, Inc. Dr. Hewett worked for 25 years as an industrial hygienist for NIOSH, in the Division of Respiratory Disease Studies, where he specialized in the measurement of pneumoconiosis producing dusts. Dr. Hewett received an MS in Industrial Hygiene from the University of Central Missouri in 1978, a PhD in industrial hygiene from the University of Pittsburgh, School of Public Health in 1991, and is the author of several articles and chapters on exposure assessment and statistics for industrial hygiene.​

Perry Logan, PhD, CIH, Senior Manager, Corporate Ergonomics and IH, Global EHS Team Leader, 3M, St. Paul, MN.

Perry is currently senior manager, 3M Corporate Industrial Hygiene. His previous experience includes industrial hygiene at complex chemical facilities, EHS consulting, hazardous waste management / operations, and emergency response. He helped integrate industrial hygiene into safety, environmental, business systems and programs through implementation of 3M’s comprehensive exposure assessment and management program (Control Banding). Perry has made numerous technical presentations on comprehensive exposure assessment, use of mathematical exposure models, surface and air sampling system technologies, and FTIR for industrial hygiene. He is a past instructor for many professional development courses. Perry is a past chair of the AIHA® Exposure Assessment Strategies Committee and the Gas and Vapor Detection Systems Committee. He earned a BS in chemical engineering, an MS in industrial hygiene and a PhD in environmental and occupational health from the University of Minnesota.