ASHRAE Journal - May 2013 - 14

LETTERS
Is CO2 Indoor Pollutant?

The Author Responds

March’s “Is CO2 Indoor Pollutant?” by William J. Fisk, et al.,
does a disservice to our industry. The column properly qualifies
itself, but many readers might end up with a false impression.
• It is easy for busy readers to miss details such as the study
size of 22 people, which is less than meaningless for engineering practice or ASHRAE standards.
• Most engineers I speak to regularly do not know the origins of
the 1,000 ppm CO2 guidelines and do not know CO2 has been used
as a convenient surrogate for other causes of adverse perception of
air quality. Many ASHRAE engineers may assume CO2 is a bona
fide pollutant similar to, but less potent than, CO. That lack of information gets coupled with a prevailing sense that, for pollutants,
“there is no ppm that is a good ppm.” Better to be safe than sorry.
• I have some bias from promoting direct-fired heating equipment, but the bias was fairly and responsibly developed by research,
observation and measurement. There are many proven advantages
to direct-fired heating, but it definitely adds CO2 to an occupied
space. The column plays into an easily made deduction that we
should “Be afraid; we have discovered CO2 will cause a certain
amount of mental impairment” and its corollary “Never use directfired heating.” Another corollary could easily be “Double or triple
the Standard 62.1 OA minimums to minimize CO2.”
James V. Dirkes II, P.E., Member ASHRAE, Grand Rapids, MI

Mr. Dirkes criticizes the small number of subjects in our
study. He may not recognize that the study is much more
powerful than a 22 person cross-sectional study. Each subject
experienced all three CO2 exposure conditions: 600 ppm;
1,000 ppm; and 2,500 ppm, yielding 66 data points. The order
of exposure was varied among subjects in order to cancel out
effects of learning or time of day. Also, with this study design,
we compare decision making performance within individuals,
e.g., each person’s performance in decision making at 600 ppm
CO2 is compared to their own performance in decision making
at 2,500 ppm CO2. Consequently, differences among people’s
innate decision-making skills do not bias the study findings.
Finally, in this laboratory setting all other environmental
conditions are maintained constant. Altogether, these features
of the study design result in a strong study. The data were
analyzed statistically and most of the findings are highly statistically significant, indicating that the number of subjects was
sufficient given the strength of the relationship between CO2
concentration and decision making. Nevertheless, all studies of
human outcomes require replication, and our article indicated
the need for replication.
William J. Fisk, Fellow ASHRAE, Berkeley, Calif.

www.info.hotims.com/44632-59

www.info.hotims.com/44632-48

14

ASHRAE Journal

May 2013



ASHRAE Journal - May 2013

Table of Contents for the Digital Edition of ASHRAE Journal - May 2013

ASHRAE Journal - May 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
VAV Reheat Versus Active Chilled Beams & DOAS
A Stable Whole Building Performance Method for Standard 90.1
Technology Award Case Studies:
PSU Design Build Project
Passive Cooling for School
Standing Columns
Building Sciences
InfoCenter
Refrigeration Applications
IAQ Applications
Engineer's Notebook
Products
Data Centers
Emerging Technologies
Classified Advertising
Advertisers Index
ASHRAE Journal - May 2013 - ASHRAE Journal - May 2013
ASHRAE Journal - May 2013 - Cover2
ASHRAE Journal - May 2013 - 1
ASHRAE Journal - May 2013 - 2
ASHRAE Journal - May 2013 - Contents
ASHRAE Journal - May 2013 - Commentary
ASHRAE Journal - May 2013 - 5
ASHRAE Journal - May 2013 - Industry News
ASHRAE Journal - May 2013 - 7
ASHRAE Journal - May 2013 - 8
ASHRAE Journal - May 2013 - 9
ASHRAE Journal - May 2013 - 10
ASHRAE Journal - May 2013 - 11
ASHRAE Journal - May 2013 - 12
ASHRAE Journal - May 2013 - 13
ASHRAE Journal - May 2013 - Letters
ASHRAE Journal - May 2013 - 15
ASHRAE Journal - May 2013 - Meetings and Shows
ASHRAE Journal - May 2013 - 17
ASHRAE Journal - May 2013 - VAV Reheat Versus Active Chilled Beams & DOAS
ASHRAE Journal - May 2013 - 19
ASHRAE Journal - May 2013 - 20
ASHRAE Journal - May 2013 - 21
ASHRAE Journal - May 2013 - 22
ASHRAE Journal - May 2013 - 23
ASHRAE Journal - May 2013 - 24
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ASHRAE Journal - May 2013 - 27
ASHRAE Journal - May 2013 - 28
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ASHRAE Journal - May 2013 - 30
ASHRAE Journal - May 2013 - 31
ASHRAE Journal - May 2013 - 32
ASHRAE Journal - May 2013 - A Stable Whole Building Performance Method for Standard 90.1
ASHRAE Journal - May 2013 - 34
ASHRAE Journal - May 2013 - 35
ASHRAE Journal - May 2013 - 36
ASHRAE Journal - May 2013 - 37
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ASHRAE Journal - May 2013 - 45
ASHRAE Journal - May 2013 - PSU Design Build Project
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ASHRAE Journal - May 2013 - 48
ASHRAE Journal - May 2013 - 49
ASHRAE Journal - May 2013 - 50
ASHRAE Journal - May 2013 - 51
ASHRAE Journal - May 2013 - 52
ASHRAE Journal - May 2013 - 53
ASHRAE Journal - May 2013 - Passive Cooling for School
ASHRAE Journal - May 2013 - 55
ASHRAE Journal - May 2013 - 56
ASHRAE Journal - May 2013 - 57
ASHRAE Journal - May 2013 - 58
ASHRAE Journal - May 2013 - 59
ASHRAE Journal - May 2013 - 60
ASHRAE Journal - May 2013 - 61
ASHRAE Journal - May 2013 - Building Sciences
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ASHRAE Journal - May 2013 - 69
ASHRAE Journal - May 2013 - InfoCenter
ASHRAE Journal - May 2013 - 71
ASHRAE Journal - May 2013 - 72
ASHRAE Journal - May 2013 - 73
ASHRAE Journal - May 2013 - 74
ASHRAE Journal - May 2013 - Refrigeration Applications
ASHRAE Journal - May 2013 - 76
ASHRAE Journal - May 2013 - 77
ASHRAE Journal - May 2013 - IAQ Applications
ASHRAE Journal - May 2013 - 79
ASHRAE Journal - May 2013 - 80
ASHRAE Journal - May 2013 - 81
ASHRAE Journal - May 2013 - 82
ASHRAE Journal - May 2013 - 83
ASHRAE Journal - May 2013 - Engineer's Notebook
ASHRAE Journal - May 2013 - 85
ASHRAE Journal - May 2013 - Products
ASHRAE Journal - May 2013 - 87
ASHRAE Journal - May 2013 - Data Centers
ASHRAE Journal - May 2013 - 89
ASHRAE Journal - May 2013 - 90
ASHRAE Journal - May 2013 - 91
ASHRAE Journal - May 2013 - Emerging Technologies
ASHRAE Journal - May 2013 - 93
ASHRAE Journal - May 2013 - 94
ASHRAE Journal - May 2013 - Classified Advertising
ASHRAE Journal - May 2013 - Advertisers Index
ASHRAE Journal - May 2013 - Cover3
ASHRAE Journal - May 2013 - Cover4
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