ASHRAE Journal - May 2022 - 49

TECHNICAL FEATURE
can also be signifi cant. Even if NO2 emissions were signifi
cantly lower than the allowable limit in Z21.11.2, CO2
would still be a critical contaminant of concern.
ASHRAE positions and policies as well as concern for
human health imply that these should be controlled to
acceptable levels. Requirements for kitchens already
exist that address this issue, but there are no requirements
for use of unvented heaters in homes. The key
conclusion from this work is as follows: Whenever the
normalized capacity of an unvented space heater is greater than
0.4 Btu/h ·ft3 (4 W/m3), operation of that heater in homes minimally
meeting ASHRAE Standard 62.2-2019 ventilation requirements
constitutes a high polluting event, even when that appliance
complies with ANSI Standard Z21.11.2.
The results would indicate that carbon monoxide is the
least important of the critical contaminants reviewed,
but prior fi eld studies25 have suggested otherwise.
This, plus the recommendations made in the Position
Document , suggest that more research on this topic
is needed to ensure that carbon monoxide does not
become a critical contaminant.
Currently, ASHRAE Standard 62.2 is silent on the
impacts of unvented space heaters, which could incorrectly
lead the public to believe they are not a known
hazard. The authors recommend that the committee
responsible for the standard upgrade the standard to
better achieve its core objective of providing acceptable
indoor air quality.
The authors also recommend that the position document
on unvented combustion be revised to refl ect
research and publications (including this analysis) since
the document was written about a decade ago. The
revised Society position on indoor air quality could also
be updated.
References
1. ANSI/ASHRAE Standard 62.2-2019, Ventilation and Acceptable
Indoor Air Quality in Residential Buildings.
2. ASHRAE. 2012 (Reaffi rmed 2020). " ASHRAE Position
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3. Dutton, S. et al. 2001. " Indoor pollutant levels from use of
unvented natural gas fi replaces in Boulder Colorado. " Journal of the
Air & Waste Management Association 51(12):1654 - 1661.
4. EPA. Undated. " NAAQS Table. " U.S Environmental Protection
Agency. https://tinyurl.com/99jwbd53
5. WHO. 2021. " Ambient (Outdoor) Air Pollution. " World Health
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Quality " ASHRAE. https://tinyurl.com/mddc9ju9
M AY 2 0 2 2 ashrae.o rg ASHRAE JOURNAL
49
7. OSHA. Undated. " OSHA Occupational Chemical Database,
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https://tinyurl.com/2p8vjp5x
8. Persily, A. 2018. " Development of an Indoor Carbon Dioxide
Metric. " 39th AIVC Conference.
9. ASHRAE. 2022. " ASHRAE Position Document on Indoor Carbon
Dioxide. " ASHRAE. https://tinyurl.com/2p97a7zw
10. EN-15251-2012, Indoor Environmental Input Parameters for Design
and Assessment of Energy Performance of Buildings Addressing Indoor Air
Quality, Thermal Environment, Lighting and Acoustics.
11. Sekhar, C., et al. 2020. " Bedroom ventilation: review of
existing evidence and current standards. " Building and Environment
184:107229. https://doi.org/10.1016/j.buildenv.2020.107229
12. Zhang, X. 2016. " Effects of Exposure to Carbon Dioxide
and Human Bioeffl uents on Health, Comfort and Cognitive
Performance. " Ph.D. Thesis. Shanghai Jiao Tong University.
13. Zhang, X.J., P. Wargocki, Z. W. Lian, C. Thyregod. 2017. " Effects
of exposure to carbon dioxide and bioeffl uents on perceived
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14. Zhang, X.J., P. Wargocki, Z.W. Lian, J.C. Xie, J.P. Liu. 2017.
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17. Thom, S., et al. 2017. " Increased carbon dioxide levels stimulate
neutrophils to produce microparticles and activate the nucleotide
binding domain-like receptor 3 infl ammasome. " Free Radical Biology
and Medicine (106):406 - 416.
18. Thom, S., et al. 2017. " Infl ammatory responses to acute
elevations of carbon dioxide in mice. " J. Appl. Physiology
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19. ASHRAE Standard 55-2020, Thermal Environmental Conditions for
Human Occupancy.
20. ASHRAE. Damp Buildings, Human Health and HVAC Design. Atlanta:
ASHRAE.
21. ASHRAE. 2012 (Reaffi rmed 2021). " ASHRAE Position Document
on Limiting Indoor Mold and Dampness in Buildings. " ASHRAE.
https://tinyurl.com/8hy7u3h8
22. EPA. Undated. " Hourly Data, Criteria Gases. " U.S.
Environmental Protection Agency. https://tinyurl.com/ytcwt4m7
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residential concentrations of combustion-generated pollutants:
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ASHRAE Journal - May 2022

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