ASHRAE Journal - April 2013 - 65

amount of the contaminant that would exist if it were
Contaminant
U.S. EPA
WHO
Health Canada
completely undiluted by air. This allows emissions
Carbon Monoxide
to be compared across appliances. It does not mean
35 ppm
25 ppm
25 ppm
(One Hour Average)
that the indoor concentrations can reach these levels.
For natural gas and propane cooking appliances
Carbon Monoxide
9 ppm
9 ppm
10 ppm
ANSI Z21.1 has a maximum carbon monoxide
(Eight Hour Average)
concentration of 0.08% (800 ppm) air-free. Per
Nitrogen Dioxide
UL 647, kerosene heaters may have a maximum
100 ppb
110 ppb
250 ppb
(One Hour Average)
air-free carbon monoxide concentration of 0.04%
(400 ppm) at maximum burner setting and 0.08% Table 1: Relevant thresholds for carbon monoxide and nitrogen dioxide.
(800 ppm) at minimum burner setting. The nitrogen dioxide limit is 0.0003 in3/Btu (0.005 cm3/kJ) at all settings. that many of the past studies were done on older units with pilot
Denatured alcohol appliances have the same limits as natural lights, which are substantially less common today.
gas and propane heaters according to UL 1370.

Current State of Knowledge
The position document next discusses research results on
emissions and indoor air concentrations of combustion products from propane and natural gas-fired heating and cooking
equipment. Research of emissions and concentrations in kerosene and denatured alcohol are not discussed due to a lack of
available material.
For heating appliances, the majority of results come from a
field study of 30 homes by Francisco, et al.1 This study found
that a number of users operated their appliances continuously
for extended periods of time—contrary to the expected and
intended use—and that it was primarily under these conditions
that carbon monoxide levels rose to above the EPA threshold
of 9 ppm as an eight-hour average.
This condition was found in 20% of test homes. The study
also found that 80% of homes had one-hour average nitrogen
dioxide levels above the new EPA outdoor threshold of 100
ppb, and 40% were above the 300 ppb level recommended
by CPSC. However, the study noted that virtually all of
the appliances tested were manufactured before the limits
on nitrogen dioxide went into force. The study also did not
measure particles.
Also cited in the position document was a modeling study
by Whitmyre and Pandian,2 which showed that there was little
risk of excessive moisture in homes with unvented space heaters. This was consistent with the results of Francisco, et al.,1
which pointed out that winters in the geographic area of the
study were very dry.
A third study cited in the position document on space heaters
was by Hedrick and Krug,3 which evaluated emissions from
different types of unvented heaters and showed that different
technologies produce greater or lesser levels of carbon monoxide and nitrogen dioxide, with there often being a tradeoff
between the two combustion products.
For cooking appliances, the research has not evaluated the
relative importance of the combustion process compared to
the cooking itself. Cooking has been identified as an important
source of pollutants with respiratory impacts. The relative impact of broilers, ovens, and range top burners depends on the
contaminant of interest. The position document also makes clear
April 2013

Ventilation

The position document next discusses the role of ventilation.
Although it does not make quantitative recommendations regarding ventilation, it does reinforce the value of good ventilation when unvented combustion is present.

Positions
While the background and review of current knowledge
are important for context, the primary product of any position
document is the set of positions themselves. Due to the complexity of the issue of unvented combustion, combined with the
range of appliances covered by the document, there are several
positions. These can be grouped as pertaining to installation/
maintenance; the buildings in which the appliances are located;
cooking; gas/propane heaters; kerosene and denatured alcohol
appliances; standards; and public awareness. Within product
categories, there are positions relating to the appliances and
positions regarding needed research.
Installation/Maintenance
The position document reiterates industry recommendations
regarding installation and maintenance, including that appliances
should be installed by a qualified installer; they should be serviced
annually; and they should not be the sole source of heating. The
document also suggests some changes to current industry guidance.
These positions include that sizing guidance for these appliances
should be reviewed due to changes in housing stock (primarily
that homes are tighter than they used to be) and that code- and
standard-making bodies should require installers to be certified.
Building
The two primary positions relating to the building are that
there should be a carbon monoxide alarm in every home and that
ventilation should be reassessed when air sealing of a building
has been done. In the case of the former, this is consistent with
a recent addendum incorporated into ASHRAE Standard 62.2,
which will be published in the 2013 edition of that standard.
Cooking
The only position taken regarding the use of cooking appliances is that electronic ignition should be preferred over pilot
ASHRAE Journal

65



ASHRAE Journal - April 2013

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

ASHRAE Journal - April 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Ground-Coupled Heat Pump and Energy Storage
Fan Efficiency Requirements for Standard 90.1-2013
Technology Award Case Studies:
Geothermal for 5 Ecosystems
Holistic HVAC Design
Standing Columns
Engineer’s Notebook
Data Centers
Emerging Technologies
IAQ Applications
Refrigeration Applications
Special Products
People
International Column
Energy Modeling
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - April 2013 - ASHRAE Journal - April 2013
ASHRAE Journal - April 2013 - Cover2
ASHRAE Journal - April 2013 - 1
ASHRAE Journal - April 2013 - 2
ASHRAE Journal - April 2013 - Contents
ASHRAE Journal - April 2013 - Commentary
ASHRAE Journal - April 2013 - 5
ASHRAE Journal - April 2013 - Industry News
ASHRAE Journal - April 2013 - 7
ASHRAE Journal - April 2013 - 8
ASHRAE Journal - April 2013 - Letters
ASHRAE Journal - April 2013 - Meetings and Shows
ASHRAE Journal - April 2013 - 11
ASHRAE Journal - April 2013 - 12
ASHRAE Journal - April 2013 - 13
ASHRAE Journal - April 2013 - Ground-Coupled Heat Pump and Energy Storage
ASHRAE Journal - April 2013 - 15
ASHRAE Journal - April 2013 - 16
ASHRAE Journal - April 2013 - I1
ASHRAE Journal - April 2013 - I2
ASHRAE Journal - April 2013 - I3
ASHRAE Journal - April 2013 - I4
ASHRAE Journal - April 2013 - 17
ASHRAE Journal - April 2013 - 18
ASHRAE Journal - April 2013 - 19
ASHRAE Journal - April 2013 - 20
ASHRAE Journal - April 2013 - 21
ASHRAE Journal - April 2013 - 22
ASHRAE Journal - April 2013 - 23
ASHRAE Journal - April 2013 - Fan Efficiency Requirements for Standard 90.1-2013
ASHRAE Journal - April 2013 - 25
ASHRAE Journal - April 2013 - 26
ASHRAE Journal - April 2013 - 27
ASHRAE Journal - April 2013 - 28
ASHRAE Journal - April 2013 - 29
ASHRAE Journal - April 2013 - 30
ASHRAE Journal - April 2013 - 31
ASHRAE Journal - April 2013 - Geothermal for 5 Ecosystems
ASHRAE Journal - April 2013 - 33
ASHRAE Journal - April 2013 - 34
ASHRAE Journal - April 2013 - 35
ASHRAE Journal - April 2013 - 36
ASHRAE Journal - April 2013 - 37
ASHRAE Journal - April 2013 - 38
ASHRAE Journal - April 2013 - 39
ASHRAE Journal - April 2013 - Holistic HVAC Design
ASHRAE Journal - April 2013 - 41
ASHRAE Journal - April 2013 - 42
ASHRAE Journal - April 2013 - 43
ASHRAE Journal - April 2013 - 44
ASHRAE Journal - April 2013 - 45
ASHRAE Journal - April 2013 - 46
ASHRAE Journal - April 2013 - 47
ASHRAE Journal - April 2013 - Engineer’s Notebook
ASHRAE Journal - April 2013 - 49
ASHRAE Journal - April 2013 - 50
ASHRAE Journal - April 2013 - 51
ASHRAE Journal - April 2013 - 52
ASHRAE Journal - April 2013 - 53
ASHRAE Journal - April 2013 - Data Centers
ASHRAE Journal - April 2013 - 55
ASHRAE Journal - April 2013 - 56
ASHRAE Journal - April 2013 - 57
ASHRAE Journal - April 2013 - 58
ASHRAE Journal - April 2013 - 59
ASHRAE Journal - April 2013 - Emerging Technologies
ASHRAE Journal - April 2013 - 61
ASHRAE Journal - April 2013 - 62
ASHRAE Journal - April 2013 - 63
ASHRAE Journal - April 2013 - IAQ Applications
ASHRAE Journal - April 2013 - 65
ASHRAE Journal - April 2013 - 66
ASHRAE Journal - April 2013 - Refrigeration Applications
ASHRAE Journal - April 2013 - Special Products
ASHRAE Journal - April 2013 - People
ASHRAE Journal - April 2013 - International Column
ASHRAE Journal - April 2013 - 71
ASHRAE Journal - April 2013 - Energy Modeling
ASHRAE Journal - April 2013 - 73
ASHRAE Journal - April 2013 - Products
ASHRAE Journal - April 2013 - 75
ASHRAE Journal - April 2013 - 76
ASHRAE Journal - April 2013 - 77
ASHRAE Journal - April 2013 - 78
ASHRAE Journal - April 2013 - Classified Advertising
ASHRAE Journal - April 2013 - Advertisers Index
ASHRAE Journal - April 2013 - Cover3
ASHRAE Journal - April 2013 - Cover4
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