ASHRAE Journal - April 2024 - 18
INFECTIOUS AEROSOL CONTROL
Column
Operating and Maintaining Building Systems
Reducing Risk With
ASHRAE Standard 241
BY MEGHAN K. MCNULTY, P.E., MEMBER ASHRAE AND WADE H. CONLAN, P.E., BCXP, MEMBER ASHRAE
ASHRAE Standard 241's requirements can make indoor spaces more resilient to the
spread of airborne infectious diseases. Buildings that comply with ASHRAE Standard
241-2023, Control of Infectious Aerosols,1 will have the capacity to respond during times
of elevated risk with systems that provide the necessary equivalent clean airflow for
infection control (VECAi). To reduce risk effectively, these systems need to operate
properly. This column explores Standard 241's requirements for operations and
maintenance in high-risk times (infection risk management mode or IRMM) and the
importance of creating a Building Readiness Plan.
Assessment, Planning and Implementation
An existing system assessment documents how the
system works: what components and engineering
controls are in place, how much outdoor air is delivered,
how well filters are installed and what their ratings (e.g.,
MERV) are, and if any additional air cleaning systems
(with effectiveness and safety determined in accordance
with Section 7.1*) are in place. Standard 241 defines each
engineering control's contribution to the delivered VECAi;
it also defines the target VECAi for the space based on the
activity and number of people. The Equivalent Clean
Airflow Calculator2 (updated in January 2024) helps
users perform the calculations to determine the amount
of VECAi systems can provide, as shown in Online Figure 1
for a classroom (see https://tinyurl.com/JournalExtras).
* Section references are to ASHRAE Standard 241-2023, Control
of Infectious Aerosols, unless otherwise noted.
18
ASHRAE JOURNAL ashrae.org A P R I L 2024
System modifications to increase equivalent clean
airflow, such as mechanical filter upgrades, ultraviolet
(UV) germicidal irradiation and in-room air cleaners
(IRACs), can be evaluated and parameters adjusted until
the delivered VECAi meets or exceeds the target VECAi.
Operating Requirements
Once engineering controls are in place, how do
you use them in IRMM? Standard 241 requires that
systems provide VECAi whenever people are present
and encourages the use of energy-efficient operating
strategies. Like requirements in ASHRAE Standard
62.1-2022, systems must provide VECAi under all
load conditions and dynamic reset conditions.3
Meghan K. McNulty is a former senior engineer with Servidyne and current building
systems engineer with Pacific Northwest National Laboratory. Wade H. Conlan is an
assistant vice president and commissioning and energy discipline manager for Hanson
Professional Services Inc.
https://tinyurl.com/JournalExtras
http://www.ashrae.org
ASHRAE Journal - April 2024
Table of Contents for the Digital Edition of ASHRAE Journal - April 2024
Contents
ASHRAE Journal - April 2024 - Intro
ASHRAE Journal - April 2024 - Cover1
ASHRAE Journal - April 2024 - Cover2
ASHRAE Journal - April 2024 - 1
ASHRAE Journal - April 2024 - Contents
ASHRAE Journal - April 2024 - 3
ASHRAE Journal - April 2024 - 4
ASHRAE Journal - April 2024 - 5
ASHRAE Journal - April 2024 - 6
ASHRAE Journal - April 2024 - 7
ASHRAE Journal - April 2024 - 8
ASHRAE Journal - April 2024 - 9
ASHRAE Journal - April 2024 - 10
ASHRAE Journal - April 2024 - 11
ASHRAE Journal - April 2024 - 12
ASHRAE Journal - April 2024 - 13
ASHRAE Journal - April 2024 - 14
ASHRAE Journal - April 2024 - 15
ASHRAE Journal - April 2024 - 16
ASHRAE Journal - April 2024 - 17
ASHRAE Journal - April 2024 - 18
ASHRAE Journal - April 2024 - 19
ASHRAE Journal - April 2024 - 20
ASHRAE Journal - April 2024 - 21
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ASHRAE Journal - April 2024 - 24
ASHRAE Journal - April 2024 - 25
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ASHRAE Journal - April 2024 - 27
ASHRAE Journal - April 2024 - 28
ASHRAE Journal - April 2024 - 29
ASHRAE Journal - April 2024 - 30
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ASHRAE Journal - April 2024 - Cover3
ASHRAE Journal - April 2024 - Cover4
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