About the Authors Thomas T. Shen is Senior Research Scientist with the New York State Department of Environmental Conservation. Dr. Shen is an Adjunct Faculty Member and Doctoral Thesis Advisor in the Division of Environmental Sciences at Columbia University. He has almost twenty years experience as a lecturer in the United States and abroad. He holds a Ph.D. in environmental engineering from Rensselaer Polytechnic Institute. Charles E. Schmidt is an independent environmental consultant in Red Bluff, California. He earned his Ph.D. in environmental chemistry from the University of Michigan. Dr. Schmidt's technical experiences have focused primarily on assessment and evaluation of atmospheric contaminant emissions from hazardous waste facilities. Thomas R. Card is with the environmental consulting company of CH2M Hill. He earned his masters in Civil Engineering at the California Institute of Technology. Mr. Card is known for his research and development regarding improved scrubber design and operation of control technologies for the removal of odorous species.