Designing Safe and Energy Efficient Laboratory Exhaust Systems

Thursday, September 21, 3:30 - 4:30 PM

Speaker(s): Brad Cochran, PE

Laboratory exhaust systems are one of the most energy intensive systems found within a wet bench laboratory. It is also one of the most important safety features of the lab since it is responsible for minimizing the re-entrainment of any toxic and/or odorous emissions at nearby air intake and other sensitive locations. Therefore, designing these systems to safe and energy efficient is key to the overall health and welfare of any laboratory building and it occupants.

This presentation will provide owners, lab designers and engineers the information necessary to understand the proper design of laboratory exhaust systems, some of the pitfalls associated with poor designs, rules of thumb that may or may not be appropriate, and methods that can be applied to reduce the energy consumption of a typical wet lab by up to 20%. The discussion will review the current methods that are available for the design of laboratory exhaust systems from rules of thumb, numerical dispersion modeling techniques, Computational Fluid Dynamic (CFD) and wind tunnel modeling. It will include discussions on the development of design criterion that are used to define the acceptable level of re-entrainment based on U.S., U.K. and European standards.

The second half of the session will focus on the process that is involved in designing energy efficient VAV exhaust systems that avoid the need for by-pass dampers in new laboratory facilities and for retrofitting constant volume extract system to VAV control in existing laboratory facilities. This will include discussions on a simple turndown approach where minimum fan speeds are established under all operating conditions, a wind responsive system that establishes minimum fan speeds as a function of wind speed and wind direction, and in situ monitoring that uses air sampling techniques to ramp fans up and down based on the constituents of the exhaust. Case studies will be presented where techniques have been implemented throughout the United States, Canada and the United Kingdom.