| |
Fume Hood Exhaust Stacks - Developing Design Criteria
for Specific Conditions to Save Energy
Simona Besnea, P.E., and
Michael Ratcliff, Ph.D., P.E., Rowan
Williams Davies & Irwin, Inc.
Fume hood exhaust containing toxic and odorous chemicals is typically
discharged to the atmosphere to protect the safety of laboratory
workers. Reentrainment of insufficiently diluted exhaust back into
the emitting building or into surrounding buildings may result in
odors or adverse health impacts. Atmospheric modeling is often performed
to evaluate fume hood exhaust dispersion. The modeling results must
be compared to design criteria based on the chemical usage in the
laboratory. In particular, if the chemicals used can be grouped
by health risk levels using control banding, then the design criteria
can be similarly adjusted to satisfy the requirements associated
with the control bands. Where fume hood exhaust can be designed
to reflect the control banding approach, savings in energy costs
and stack height requirements can be possibly achieved.
This presentation discusses recommended design criteria for fume
hood exhaust, considerations involved in adjusting the criteria
and potential energy savings as they relate to safe implementation
of VAV systems and manifolded exhausts. The presentation will show
that based on the specific needs of the project, design criteria
can be developed in a number of ways:
- By conducting a detailed analysis of the chemicals to determine
limiting exposure limits
- By recommending, where practical (i.e., only a few toxic chemicals
require high dilutions) usage controls to reduce emissions
- If requested by the design team, considering only specific potential
effects (e.g., only health and not odors) in the assessment
The presentation will also discuss example design criteria developed
for a specific set of conditions and will quantify implications
in terms of stack height reduction, fan power required and energy
savings. To address potential changes in chemical usage, we will
present a tool that can be made available to lab owners/users for
reevaluation of the criteria.
Labs21 Connection:
Our approach of the fume hood exhaust stack design focuses on two
important aspects: safety and energy efficiency. In providing a
balanced approach, we present methods for evaluating and refining
the design criteria to answer the specific needs of the project.
Stack height optimization, flexibility for future use, and energy
savings are derived benefits.
This presentation directly reflects the following aspects of the
Labs21 Approach:
- Energy-efficient design/reduced operating costs - Detailed assessment
of the fume hood exhaust and development of design criteria for
specific set of conditions will help limit over-designing, and
will result in lower energy and equipment costs.
- Minimize environmental impacts - Implementation of an exhaust
system that provides appropriate levels of dispersion will prevent
degradation of local air quality and environmental impacts.
- Adopt voluntary goals - Optimization of the exhaust design relies
on due diligence and voluntary compliance of building designers
and owners.
- Community support and relations - A high performance stack design
will facilitate understanding of the project by the community
and enhance public support.
Biographies:
Simona Besnea has a B.Sc. in Engineering
Physics from the University of Bucharest, Romania, and is currently
completing her M.Eng. in Environmental Engineering at the University
of Guelph, in Ontario, Canada. The focus of Ms. Besnea's research
is air quality and dispersion modeling. Ms. Besnea is a Professional
Engineer within the province of Ontario and is currently a Senior
Engineer in the Wind Air and Microclimate Division at Rowan Williams
Davies & Irwin Inc. in Guelph, Ontario, Canada. She focuses
primarily on numerical and physical air quality modeling, specializing
in exhaust reentrainment studies for the design of building exhaust
and air intake systems for laboratories, hospitals, and other related
facilities.
Michael Ratcliff has a Ph.D. in
Civil Engineering from Colorado State University and has been a
practicing consultant in air quality and building design for 22
years. Dr. Ratcliff is a registered Professional Engineer in four
states and has been a Senior Specialist with Rowan Williams Davies
& Irwin, Inc. since 1998. He has been an active member of ASHRAE
since 1991. The focus of his consulting work is numerical and physical
air quality modeling for exhaust systems at laboratories, hospitals,
and other institutional facilities.
Back to Agenda
|
