Characterizing Risk and Future Flexibility in Laboratory Exhaust Design

Ruth McMath, RWDI

How is acceptability defined for a laboratory ventilation system? Safe dispersion of exhaust with potentially high chemical concentrations is often referred to in the context of meeting occupational health-based exposure criteria, but this approach may fail to account for other concerns such as odors, or long-term exposure. Additionally, these criteria vary widely for different chemicals. Ultimately, achieving a safe, effective, and energy-efficient dispersion of laboratory exhausts involves a broad array of considerations, all of which can impact the flexibility of the laboratory to accommodate changes in use over its lifespan. Designing a highly robust exhaust system provides more flexibility, but can come at a high cost in terms of energy and aesthetics. Conversely, a system that is highly energy efficient may put significant onus on the users of the space to ensure controls are used effectively and protocols adhered to.

This presentation will explore the challenges of characterizing risk from laboratory activities, how these risks influence the potential for energy use reduction, and how these issues can potentially be overcome without over-designing exhaust systems. By developing a better understanding of the types and intensity of chemical use, along with the sensitivity of the laboratory users and neighboring populations, more information becomes available on the applicability of various benchmarks for achieving 'good' dispersion of the exhaust. Three theoretical case studies will be presented to illustrate these concepts: a research-intensive clean room, an undergraduate teaching laboratory, and a small diagnostics laboratory tenant in a multi-use urban building. Participants will be guided through key aspects of each case study that illustrate different control strategies and the trade-offs between efficiency, flexibility, and cost with respect to the laboratory exhaust system design.

Learning Objectives

  • Be able to identify the extent to which risks vary based on specific laboratory activities;
  • Better understand the importance of characterizing risk as a means of defining acceptability for performance of laboratory exhausts;
  • Acquire a deeper knowledge of how laboratory exhaust design can be fine-tuned to accommodate varying risk levels; and
  • Gain an appreciation of trade-offs required to achieve long-term flexibility in laboratory use.


Ruth is an experienced air quality specialist who supports clients' laboratory performance objectives by using wind tunnel and numerical dispersion modeling methods to find the optimal design solution for each context. In her work on institutional, healthcare, and private laboratories, Ruth combines expertise in microclimates and exhaust re-entrainment with practical insights to help achieve technical excellence in a range of application.


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