United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S9-87/005 Apr. 1987
&EPA Project Summary
Pollutant Emission Factors for
Gas Stoves: A Literature Survey
Cliff I. Davidson, John E. Borrazzo, and Chris T. Hendrickson
Published emission factors for CO,
NO, NO2, NOX have been summarized
for gas-fired kitchen stoves. Analysis of
variance was then used to investigate
the importance of three binary factors:
type of combustion, burner position,
and method of sampling. The emission
factor data were then used to estimate
coefficients in various multivariate re-
gression models. The influence of gas
flow rate on emission factors was in-
vestigated separately. The data were
also used to investigate the sensitivity
of predicted airborne concentrations to
uncertainties in emission factors. Final-
ly, the data were used to identify critical
gaps in understanding emission factors.
This Protect Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).
The Survey
Published emission factors for CO, NO,
N02, and NOX for gas-fired kitchen stoves
have been summarized. To the extent
that data exist, the emission factors have
been used in a statistical analysis to
investigate the most important factors
influencing emissions.
First, the data were used to construct
normal probability and log probability plots
based on the cumulative distribution of
the emission factors. Correlation coef-
ficients were computed for both types of
plots. Results showed that the log prob-
ability plot provided a better fit to the CO
and NO2 data with reasonably high cor-
relation coefficients, suggesting that the
emission factors for these pollutants may
be approximated by lognormal distribu-
tions. Either normal or lognormal distri-
butions were satisfactory for NO and
NOX. For consistency, the emission fac-
tors for all four pollutants were assumed
to be distributed lognormally in sub-
sequent analysis.
Analysis of variance was then used to
investigate the importance of three binary
factors in explaining the observed vari-
ations in emissions: (1) type of combustion
(poorly adjusted or well adjusted), (2)
burner position (front or rear), and (3)
method of sampling (direct or indirect).
The results showed that roughly half of
the observed variance in log EF (base 10
logarithm of the emission factor) for CO
can be explained by noting if the com-
bustion is poorly adjusted. For N02,
roughly 30% of the variance can be ex-
plained by this factor. For NO and NOX,
the fraction of variance explained by this
factor depends on the subset of the data
chosen: fractions ranged from 0.088 to
0.56. Burner position and method of
sampling were both relatively unim-
portant in explaining the observed vari-
ance for any of the four pollutants.
The emission factor data were then
used to estimate coefficients in various
multivariate regression models. The first
regression model incorporated several
factors: type of combustion, burner posi-
tion, method of sampling, the three two-
way interactions between these factors,
and (M-1) binary factors corresponding to
the M stoves for which data were avail-
able (M=27, 26, 26, and 8 for CO, NO,
N02 and NOX, respectively). Subsequent
multivariate regression models were
constructed by sequentially eliminating a
factor or factors from the previous model.
Results of these tests showed that stove
differences were significant at the 95%
level in explaining the variance in CO,
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N02, and NOX emission factor. Type of
combustion was significant for CO, NO,
and N02. Burner position had a smaller
but still statistically significant effect in
explaining the variance 'in CO and N02
emissions. Similarly, the method of sam-
pling had a small but statistically signifi-
cant effect for NOX emissions.
The influence of gas flow rate on emis-
sion factors was investigated separately.
Statistical tests were not run for this
factor due to both a lack of data and the
presence of detailed data from only one
study. Results of plotting all of the data
for each pollutant on a common graph
showed that CO and N02 emissions vary
considerably with gas flow rate, while
emissions of NO and NOX are less
variable.
The data were used to investigate the
sensitivity of predicted airborne concen-
trations to uncertainties in emission
factors. The solution of a one-compart-
ment mass balance model was used as
the predictor of concentration. For the
existing distribution of emission factor
data, the current uncertainty in CO is
responsible for a larger fraction of the
variance in predicted concentration than
uncertainty in air exchange rate. For NO
and NO2, however, the uncertainty in air
exchange rate is more important than the
emission factor uncertainties.
Finally, the data were used to identify
critical gaps in understanding emission
factors and to suggest future experiments.
Overall, it is concluded that the influence
of stove design, gas flow rate, and char-
acteristics of stove use are key factors
which merit further study.
C. Davidson, J. Borrazzo, and C. Hendrickson are with Carnegie-Mellon
University, Pittsburgh, PA 15213.
Jane M. Crum is the EPA Project Officer (see below).
The complete report, entitled "Pollutant Emission Factors for Gap Stoves: A
Literature Survey," (Order No. PB 87-171 328/AS; Cost: $18.95, subject
to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory Laboratory
U.S. Environmental Protection Agency
ResearchJriangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S9-87/005
0000329 PS
U S ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
230 S DEARBORN STREET
CHICAGO IL 60604
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