Best Practices for Modeling Exhaust Dispersion

Ronald Petersen, Cermak, Peterka, Petersen, Inc.

Objectives:

This objectives of this presentation are to:

1. Provide a general understanding of air flow around buildings;
2. Provide qualitative information to judge whether exhaust designs are acceptable from an air quality perspective;
3. Provide information to help develop health and odor concentration design criteria;
4. Provide knowledge about how concentration levels due to building exhausts are estimated at air intakes and other sensitive locations. This presentation will also provide the attendees information so they can spot potential air quality problems at a facility and know what methods are available to assess and solve noted problems.

Findings:

This presentation will describe the new Labs21 Best Practices guide for modeling exhaust dispersion. Accurate modeling of exhaust dispersion is needed to ensure concentration levels at air intakes and other sensitive locations do not exceed health or odor limits. The methods available for predicting exhaust plume rise and the concentration levels at air intakes and other sensitive locations will be described along with their advantages and disadvantages. The effects of building shape, screens around the stack, intake location, volume flow, exit velocity, chemical utilization, and local meteorology on exhaust dispersion will also be discussed. A step by step approach is provided that includes an initial qualitative assessment of the exhaust/intake design, development of a minimum acceptable concentration for each exhaust, predicting concentrations at intakes and other locations, comparing the predicted concentrations against the criterion, and modifying the design until the criterion is reached. Copies of the Best Practices guide will be available.

Labs21 Connection:

• Reduced operating costs: By using the appropriate approach, fan sizes can be minimized which will result in lower energy costs.
• Improved environmental quality: Again, using the appropriate method will ensure that concentration levels due to laboratory pollutants will not exceed health and odor limits at intakes and other sensitive locations (entrances, plazas, windows, etc.)
• Increased health, safety, and productivity. An accurate assessment of the exhaust system will help ensure toxic or odorous fumes do reenter the building through air intakes, windows or doors.
• Enhanced community relations. When neighbors see an exhaust stack, they wonder what is coming out. Am I safe? A knowledge of the air quality impacts can be used to educate the community and tell them they are not at risk (if true).
  Superior recruitment and retention of scientists. Buildings that have health or odor problems due to fume reentry will not promote recruitment and retention.

Biography:

Dr. Ron Petersen has a B.S. in mathematics from the South Dakota School of Mines and Technology, an M.S. in Atmospheric Science from the South Dakota School of Mines and Technology and a Ph.D. in Civil Engineering (Specialty in Wind Engineering) from Colorado State University. Dr. Petersen is a Vice President and Principal at Cermak Peterka Petersen, Inc.(CPP), a firm that specializes in providing design information to account for the effect of wind on man and his environment. One of the areas that Dr. Petersen specializes in is providing design information for new and existing laboratories or hospitals so that the air quality impact of building exhausts can be minimized at nearby air intakes and other sensitive locations (i.e., operable windows, entrances, plazas, walkways, etc.). Some of the projects he has worked on include NREL's new Science and Technology Facility, Lawrence Berkeley's new Molecular Foundry, CDC Building 110, Cornell's Duffield Hall, National Institutes of Health Clinical Research Center, the UCLA Westwood Replacement Hospital, M.D. Anderson Cancer Research Center in Houston and the Fred Hutchinson Cancer Research Center in Seattle. He also was the principal investigator on two ASHRAE research projects. The first project developed general exhaust stack guidelines to account for the effect of architectural screens. The second project looked at the benefit of hidden versus visible air intakes.

Dr. Petersen is also actively involved in several professional organizations to include AMS, ASHRAE, A&WMA, ISPE and AIHA. In 1996, Dr. Petersen was the program chairman for the Ninth Joint Conference on Air Pollution Meteorology and in 2000 helped coordinate and provide comments on behalf of the Air & Waste Management Association's meteorology committee for presentation at the 7TH EPA Modeling Conference regarding revisions to EPA's "Guideline on Air Quality Modeling." He has also served or is serving on committees related to pollutant dispersion and fume reentry for ASHRAE, AMS and A&WMA. Dr. Petersen has also presented a short course on fume reentry for the AIHA and has presented at several past Labs21 Conferences. He has authored or coauthored more than 300 papers and technical reports including technical papers regarding minimizing pollutant reentry into buildings. Much of this work was summarized in a recent ASHRAE Journal article.