ASHRAE Journal - September 2019 - 70

COLUMN PRODUCTIVITY-ASHRAE

Editor's Note: The following columns regarding indoor air quality and occupant productivity appear in the September issues of
ASHRAE Journal and CIBSE Journal.

Do Indoor CO2 Levels
Directly Affect Perceived
Air Quality, Health, or
Work Performance?
BY WILLIAM FISK, FELLOW/LIFE MEMBER ASHRAE; PAWEL WARGOCKI, PH.D., ASSOCIATE MEMBER ASHRAE; XIAOJING ZHANG

This article summarizes the findings of 10 recent studies investigating whether
increased carbon dioxide (CO2) concentrations, with other factors constant, influence
perceived air quality, health, or work performance of people.
Concentrations of CO2 in occupied buildings exceed
outdoor concentrations because CO2 is a product of
peoples' metabolism. Indoor CO2 concentrations are
indicators of the rates of building ventilation with outdoor air per person. A higher indoor CO2 concentration is often considered an indicator of poorer indoor
air quality (IAQ), although many factors unrelated to
indoor CO2 concentrations influence IAQ. When indoor
CO2 concentrations increase and decrease, concentrations of other indoor air pollutants emitted from indoor
sources, particularly the bioeffluents from humans,
may also increase and decrease. Increased indoor CO2
concentrations have often been associated (correlated)
with decreases in perceived air quality, with increases in
acute health symptoms, and with reductions in aspects
of human performance.1-3 Research prior to 2012,
indicated that levels of CO2 itself, with other conditions constant, had no significant impacts on peoples'
health or performance unless the CO2 concentrations
far exceeded the levels found in buildings.4-10 The
occupational limit for CO2 in the U.S. is 5,000 ppm
for a 40 hour workweek.11 Therefore, the previously
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documented associations of indoor CO2 concentrations
with perceived air quality, health symptoms, and performance have been attributed to the other indoor air
pollutants with changes in concentrations indicated by
the changes in indoor concentrations of CO2.
Since 2012, 10 studies12-23 have investigated whether
increases in moderate CO2 concentrations, with other
conditions constant, adversely influence perceptions
of indoor air quality, health, or cognitive performance
in humans. The study features are described in Table 5
in the IAQScience website.24 These studies have been
performed with subjects in research facilities enabling
CO2 concentrations to be modified by adding pure CO2
to indoor air while maintaining all, or nearly all, other
conditions constant. By providing high ventilation rates,
these studies have maintained low concentrations of
bioeffluents. All studies maintained subjects unaware
of the CO2 concentrations. All studies recruited healthy
William Fisk is a senior scientist at Lawrence Berkeley National Laboratory, Berkeley,
Calif. Pawel Wargocki, Ph.D., is an associate professor at Technical University of Denmark,
Lyngby, Denmark. Xiaojing Zhang is an assistant professor at Beijing University of
Technology, Beijing, China.


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ASHRAE Journal - September 2019

Table of Contents for the Digital Edition of ASHRAE Journal - September 2019

Contents
ASHRAE Journal - September 2019 - Intro
ASHRAE Journal - September 2019 - Cover1
ASHRAE Journal - September 2019 - Cover2
ASHRAE Journal - September 2019 - 1
ASHRAE Journal - September 2019 - Contents
ASHRAE Journal - September 2019 - 3
ASHRAE Journal - September 2019 - 4
ASHRAE Journal - September 2019 - 5
ASHRAE Journal - September 2019 - 6
ASHRAE Journal - September 2019 - 7
ASHRAE Journal - September 2019 - 8
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ASHRAE Journal - September 2019 - Cover3
ASHRAE Journal - September 2019 - Cover4
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