ASHRAE Journal - February 2013 - 75

iaq applications

What We Know
Can Hurt Us
I
By Max Sherman, Ph.D., Fellow ASHRAE

f one listens to many who study indoor air quality, it would be possible to
think we know almost nothing1 about the subject. We hear that there are

thousands of compounds in the indoor air, and we know little about most of
them.2 We know even less about interactions of contaminants with other fac-

tors.3 We don’t know what we think we know—let alone what we don’t know.
Although it is true that things are complicated and that everything mentioned
in various extensive documents, such as
ASHRAE Guideline 104, might be relevant, in some cases a kind of paralysis
sets in; we want to avoid a situation where
best gets in the way of good, which can
happen when focusing on what we don’t
know as opposed to what we do. Although
we don’t know everything we would like
to know, we know enough5 to make some
reasonable engineering decisions on IAQ
that we expect will improve the situation.
I am a researcher and make a living
trying to discover new information about
HVAC and related building science issues,
particularly those things that can help us

make buildings better by providing improved building services at lower energy
and other environmental impacts. To that
end, we have been looking at ways to treat
the chronic6 health impacts associated with
indoor air in a quantitative way so the kind
of engineering principles that ASHRAE
members apply in other aspects of HVAC
could be applied to indoor air quality.
Chronic health impacts are not easy
for the occupant to physically appreciate
because the exposure may take many
years to cause observable health impacts
and may not even be present when the
health impacts become apparent. In
fact, the health effects may be triggered
by a relatively minor but acute incident

of a completely different nature. The
individual may attribute the problem to
the acute contaminant when, in fact, the
problem was primarily due to the longerterm chronic exposure of another.7 From
a health perspective, dilution ventilation
such as that required by ASHRAE Standard 62 is not intended to mitigate large
intermittent releases of contaminants but
to mitigate chronic exposures.8
A couple of years ago I reported9 about
the things we were finding in indoor air,
particularly those that exceeded relevant
standards. From that investigation we determined a kind of Top Ten of contaminants
for indoor air. These contaminants were ones
that were known to exceed existing standards across the population of buildings.10
That study assumed that violating the
(chronic) standard for one contaminant
was just as bad as violating the standard
for another. Surprisingly, that seemingly
reasonable assumption turn out to be
not at all true.11 So, we needed to find
a method of putting health effects from
different contaminants on a comparable
footing so that optimizing could be done.
To do this requires linking together a
set of disciplines including exposure science, toxicology, epidemiology, as well
as health and medical sciences. We had
expected to find the foundational work
had been done, but it was not.12 So, we
put together the pieces ourselves;13 in
doing so we found that sociologists and
economists had already taken the final

1We

don’t know what we don’t know, but some think there is a lot of that. But, of course, we don’t know. 2We know there are compounds that we don’t know
enough, but there is some, where we know what we need to know. 3We don’t know if we know enough about these other things, but we also don’t know if we
need to know. Although there seem to be a lot of IAQ experts who embrace not knowing. 4ASHRAE Guideline 10-2011, Interactions Affecting the Achievement
of Acceptable Indoor Environments. 5OK, OK enough of this “knowing.” You know where it all comes from anyway. 6It is important to differentiate the impacts of
acute and chronic exposures and their health impacts. Acute exposures are those that happen over a relatively short period of time: minutes or hours or a day.
Generally, the health impacts from acute exposures show up rather quickly and can be directly tied to the exposure. Irritation, discomfort, difficulty in breathing
or even death can be directly correlated with an immediate acute exposure to some contaminant. Generally, the body can mostly recover from non-lethal exposures to indoor contaminants and the damage is relatively short-term and identifiable. Chronic exposures, on the other hand, are ones that accrue over a long
period of time and tend to accumulate in the body. Although the body may be able to partially mitigate the damage due to these exposures, the chronic health
impact is that which the body cannot mitigate. Designers need to account for both acute and chronic exposures. An exhaust hood, for example, is the solution to
mitigate acute exposure to a known intermittent source. 7The straw-exposure that broke the chronically loaded camel’s back, as it were. 8It is also intended to address “perceived air quality” (i.e., odors), but I am only addressing health issues here. 9Sherman, M. 2010. “What’s in Air We Breathe.” ASHRAE Journal 52(11).
10That study focused mostly on homes. It is certainly true that some other occupancies will have distribution of pollutants that may differ, the population, as a
whole, spends more time in dwellings than in all other building types combined. Accordingly, we will, for the moment, assume that residential exposures are
representative of total indoor exposures for the population as a whole. By doing so we explicitly exclude the exposures of special populations. 11Turns out that
standard setting is political; who knew? The standard set for a given contaminant is done by a group of both knowledgeable and affected parties. Each standard is set by a unique consideration of the perceived costs of meeting and violating the standard, as well as the benefits. This is seemingly done independently
of the impact that other relevant standards might have. 12Turns out that disciplinary boundaries in these fields are highly defended; who knew? Each discipline
has its own jargon and its own journals and tends to discourage the very kind of coupling we were looking for. We faced this when trying to publish our work.
13Logue, J.M., et al. 2011. “Hazard assessment of chemical air contaminants measured in residences.” Indoor Air 21(2):92–109.

February 2013

ASHRAE Journal

75



ASHRAE Journal - February 2013

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

Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
R-22 Hard Act to Follow: Ammonia Low-Pressure Receiver Systems
Long-Term Commercial GSHP Performance: Part 7: Achieving Quality
Thermally Active Floors: Part 2: Design
Future of DCV for Commercial Kitchens
Standing Columns and Special Sections
Building Sciences
Emerging Technologies
ACREX India 2013 Show Guide
Refrigeration Applications
InfoCenter
Data Centers
IAQ Applications
Special Products
Classified Advertising
Advertisers Index
ASHRAE Journal - February 2013 - Intro
ASHRAE Journal - February 2013 - Cover1
ASHRAE Journal - February 2013 - Cover2
ASHRAE Journal - February 2013 - 1
ASHRAE Journal - February 2013 - 2
ASHRAE Journal - February 2013 - Contents
ASHRAE Journal - February 2013 - Commentary
ASHRAE Journal - February 2013 - 5
ASHRAE Journal - February 2013 - Industry News
ASHRAE Journal - February 2013 - 7
ASHRAE Journal - February 2013 - 8
ASHRAE Journal - February 2013 - 9
ASHRAE Journal - February 2013 - 10
ASHRAE Journal - February 2013 - 11
ASHRAE Journal - February 2013 - Letters
ASHRAE Journal - February 2013 - 13
ASHRAE Journal - February 2013 - Meetings and Shows
ASHRAE Journal - February 2013 - 15
ASHRAE Journal - February 2013 - R-22 Hard Act to Follow: Ammonia Low-Pressure Receiver Systems
ASHRAE Journal - February 2013 - 17
ASHRAE Journal - February 2013 - 18
ASHRAE Journal - February 2013 - 19
ASHRAE Journal - February 2013 - 20
ASHRAE Journal - February 2013 - 21
ASHRAE Journal - February 2013 - 22
ASHRAE Journal - February 2013 - 23
ASHRAE Journal - February 2013 - 24
ASHRAE Journal - February 2013 - 25
ASHRAE Journal - February 2013 - Long-Term Commercial GSHP Performance: Part 7: Achieving Quality
ASHRAE Journal - February 2013 - 27
ASHRAE Journal - February 2013 - 28
ASHRAE Journal - February 2013 - 29
ASHRAE Journal - February 2013 - 30
ASHRAE Journal - February 2013 - 31
ASHRAE Journal - February 2013 - 32
ASHRAE Journal - February 2013 - 33
ASHRAE Journal - February 2013 - 34
ASHRAE Journal - February 2013 - 35
ASHRAE Journal - February 2013 - Thermally Active Floors: Part 2: Design
ASHRAE Journal - February 2013 - 37
ASHRAE Journal - February 2013 - 38
ASHRAE Journal - February 2013 - 39
ASHRAE Journal - February 2013 - 40
ASHRAE Journal - February 2013 - 41
ASHRAE Journal - February 2013 - 42
ASHRAE Journal - February 2013 - 43
ASHRAE Journal - February 2013 - 44
ASHRAE Journal - February 2013 - 45
ASHRAE Journal - February 2013 - 46
ASHRAE Journal - February 2013 - 47
ASHRAE Journal - February 2013 - Future of DCV for Commercial Kitchens
ASHRAE Journal - February 2013 - 49
ASHRAE Journal - February 2013 - 50
ASHRAE Journal - February 2013 - 51
ASHRAE Journal - February 2013 - 52
ASHRAE Journal - February 2013 - 53
ASHRAE Journal - February 2013 - 54
ASHRAE Journal - February 2013 - 55
ASHRAE Journal - February 2013 - Building Sciences
ASHRAE Journal - February 2013 - 57
ASHRAE Journal - February 2013 - 58
ASHRAE Journal - February 2013 - 59
ASHRAE Journal - February 2013 - 60
ASHRAE Journal - February 2013 - 61
ASHRAE Journal - February 2013 - 62
ASHRAE Journal - February 2013 - Emerging Technologies
ASHRAE Journal - February 2013 - 64
ASHRAE Journal - February 2013 - ACREX India 2013 Show Guide
ASHRAE Journal - February 2013 - 64b
ASHRAE Journal - February 2013 - S1
ASHRAE Journal - February 2013 - S2
ASHRAE Journal - February 2013 - S3
ASHRAE Journal - February 2013 - S4
ASHRAE Journal - February 2013 - S5
ASHRAE Journal - February 2013 - S6
ASHRAE Journal - February 2013 - S7
ASHRAE Journal - February 2013 - S8
ASHRAE Journal - February 2013 - S9
ASHRAE Journal - February 2013 - S10
ASHRAE Journal - February 2013 - S11
ASHRAE Journal - February 2013 - S12
ASHRAE Journal - February 2013 - S13
ASHRAE Journal - February 2013 - S14
ASHRAE Journal - February 2013 - S15
ASHRAE Journal - February 2013 - S16
ASHRAE Journal - February 2013 - S17
ASHRAE Journal - February 2013 - S18
ASHRAE Journal - February 2013 - S19
ASHRAE Journal - February 2013 - S20
ASHRAE Journal - February 2013 - S21
ASHRAE Journal - February 2013 - S22
ASHRAE Journal - February 2013 - Refrigeration Applications
ASHRAE Journal - February 2013 - InfoCenter
ASHRAE Journal - February 2013 - 67
ASHRAE Journal - February 2013 - 68
ASHRAE Journal - February 2013 - 69
ASHRAE Journal - February 2013 - 70
ASHRAE Journal - February 2013 - 71
ASHRAE Journal - February 2013 - Data Centers
ASHRAE Journal - February 2013 - 73
ASHRAE Journal - February 2013 - 74
ASHRAE Journal - February 2013 - IAQ Applications
ASHRAE Journal - February 2013 - 76
ASHRAE Journal - February 2013 - 77
ASHRAE Journal - February 2013 - Special Products
ASHRAE Journal - February 2013 - Classified Advertising
ASHRAE Journal - February 2013 - Advertisers Index
ASHRAE Journal - February 2013 - Cover3
ASHRAE Journal - February 2013 - Cover4
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