Designing Safe and Energy-Efficient Laboratory Exhaust Systems

The ventilation system is the lifeblood of any laboratory building. It can also be extremely energy intensive if not properly implemented. While the exhaust side of the ventilation system is critical to maintaining a safe and healthy work environment, it can be responsible for up to 30% of the laboratory's total electrical energy consumption. If the exhaust system is not properly designed, unacceptable levels of the exhaust may be re-entrained back into the laboratory, or neighboring building, creating an unhealthy environment. On the other hand, if the system is over designed it can lead to high capital costs and excessive on-going energy consumption.

This workshop will offer new advancements in designing safe and energy-efficient laboratory exhaust systems, including:

  • Best practice design guidelines for exhaust stack and air intake placement;
  • Developing health and odor acceptance criteria to ensure a safe working environment;
  • An overview of the wind climate conditions to be taken into account when designing an exhaust system;
  • Determining the best dispersion model for predicting concentrations at the nearby air intake to be used for specific applications; and
  • Control strategies that can be used, in part or in whole, during the design of a new laboratory or the renovation of an existing laboratory:
      • Strategy 1. Variable air volume (VAV) exhaust with single minimum set point (Simple Turndown).
      • Strategy 2. Real-time VAV control with variable minimum set point (Wind Responsive or In-Situ Monitoring).

These strategies can safely reduce the energy consumption of the exhaust system by about 50 percent compared to a typical constant volume system, which equates to approximately a 15 percent reduction in the laboratory's total electrical energy use.

The workshop will include examples of case studies that demonstrate how these design strategies should be implemented.

Upon completion of this workshop, attendees should be able to:

  • Be familiar with plume dispersion principles, which will aid in understanding the optimum placement of exhaust fans and air intakes to minimize fan energy requirements.
  • Select the appropriate method for evaluating the air quality versus fan energy savings.
  • Identify which exhaust systems can provide the most energy savings and the best return on investment.
  • Evaluate the best VAV exhaust strategy for their application.



Brad Cochran has nearly 25 years of experience conducting wind tunnel and numerical modeling studies related to laboratory exhaust design. He is a registered Professional Engineer with the state of Colorado; serves on the ASSE Z9.5 Laboratory Ventilation sub-committee; primary author of Chapter 9 – Exhaust Stack Design in the 2015 ASHRAE Laboratory Design Guide, and is the current vice-chair of the ASHRAE TC-9.10 Laboratory Ventilation Technical Committee. He is also the lead author on the 2011 edition of the Labs21 Best Practice Guide "Modeling Exhaust Dispersion for Specifying Acceptable Exhaust/Intake Design". Brad also served on the AMCA Induced Flow Fan CRP Committee that developed AMCA Standard 260-07, "Laboratory Methods of Testing Induced Flow Fans for Rating."

In 2011, Mr. Cochran received an individual Go Beyond Award from I2SL.

During the past decade, Mr. Cochran has focused on defining new design techniques to minimize the energy requirements for laboratory exhaust systems. In 2005, Mr. Cochran developed the first laboratory exhaust system that utilized local wind data to minimize exhaust fan horsepower requirements, and in 2008 introduced the concept of monitoring chemical constituents within the exhaust manifold to reduce volume flow rates when the exhaust is essentially "clean." Since then, Brad has implemented VAV controls in over 100 exhaust systems throughout the U.S., Canada, and the U.K.

Mr. Cochran has authored and presented several papers on the subject of energy-efficient laboratory exhaust design for the American Society of Heating, Refrigerating and Air-Conditioning Engineers Inc. (ASHRAE), I2SL, R&D Magazine, Lab Manager Magazine, LabWize, the International Facility Management Association, Air Movement and Control Association International, Inc., and the Air and Waste Management Association.


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