ASHRAE Journal - September 2020 - 60
ENGINEERS NOTEBOOK
COLUMN
Nathan Ho
Performance-Based
Approach to Laboratory
Exhaust Systems
BY NATHAN HO, P.E., MEMBER ASHRAE
Laboratory facilities serve as a critical nexus for innovation and discovery, but they
often come with the potential for high operational cost (HVAC energy consumption)
and high risk (air quality performance). A prescriptive approach to designing laboratory exhaust stacks has been common. It will likely have a place in the future based on
the need for broadly applicable minimum design criteria that can be enforced consistently through code adoption and inspectors. However, achieving superior energy
performance and acceptable air quality requires a performance-based approach to
laboratory exhaust stack design.
Examples of Prescriptive Design Criteria
A performance approach begins with an understanding
of the origins and limitations of prescriptive design criteria. Local code and recognized industry standards often
serve as the basis of prescriptive criteria a designer would
use to design a laboratory exhaust stack. Let us examine the California Mechanical Code, California Energy
Code and the American National Standards Institute/
American Industrial Hygiene Association Standard for
Laboratory Ventilation (ANSI/AIHA Z9.5) as examples.
2019 California Energy Code2
2019 California Mechanical Code1
"502.2.2 Product Conveying Ducts. Ducts conveying
explosive or flammable vapors, fumes or dusts shall
terminate not less than 30 ft (9 m) from a property line,
10 ft (3 m) from openings into the building, 6 ft (2 m)
60
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from exterior walls or roofs, 30 ft (9 m) from combustible walls or openings into the building that are in the
direction of the exhaust discharge and 10 ft (3 m) above
adjoining grade. (Emphasis is the author's.)
Other product-conveying outlets shall terminate not
less than 10 ft (3 m) from a property line, 3 ft (914 mm)
from exterior walls or roofs, 10 ft (3 m) from openings
into the building and 10 ft (3 m) above adjoining grade."
(Emphasis is the author's.)
SEPTEM BER 2020
"140.9 (c) Prescriptive Requirements for Covered
Processes, Prescriptive Requirements for Laboratory
and Factory Exhaust Systems.
Nathan Ho, P.E., is an associate principal and engineering group leader with P2S Inc., in Irvine,
Calif. He is the chair of ASHRAE SPC 110.
http://ashrae.org
ASHRAE Journal - September 2020
Table of Contents for the Digital Edition of ASHRAE Journal - September 2020
Contents
ASHRAE Journal - September 2020 - Intro
ASHRAE Journal - September 2020 - Cover1
ASHRAE Journal - September 2020 - Cover2
ASHRAE Journal - September 2020 - 1
ASHRAE Journal - September 2020 - Contents
ASHRAE Journal - September 2020 - 3
ASHRAE Journal - September 2020 - 4
ASHRAE Journal - September 2020 - 5
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ASHRAE Journal - September 2020 - Cover3
ASHRAE Journal - September 2020 - Cover4
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