ASHRAE Journal - September 2014 - 94

COLUMN IAQ APPLICATIONS

Number of Reported Non-Fire
CO Deaths Due to Generators

120

103

100

80
60

40
20 6
0
1999

21 23

2001

2003

2005

2007

2009

34
2011

Reporting for years 2011 and 2012 is considered incomplete and is likely to
change in future reports.
Reporting for years 1999 - 2010 is considered largely complete but may change
to a relatively small extent in future reports.
FIGURE 1 Increase in generator-related CO poisoning deaths since 1999.1

PHOTO 1 Generator in test shed.

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O2 (Percent)

CO (mg/m3)

Figure 2 shows the measured CO and O2
35,000
21
concentrations for two of the experiments
20.5
30,000
with the first, unmodified generator (see
20
25,000
19.5
Emmerich, et al.2 for an explanation of the
Generator On (Test 1)
Generator Off (Test 1) 19
test conditions). For reference, a CO concen20,000
18.5
tration of 1200 ppmv (which is equivalent
Generator On (Test 13)
Zero Load Output (Test 13)
15,000
18
3 in Figure 2) is considered
to 1400 mg/m
17.5
10,000
immediately dangerous to life or health
17
(http://tinyurl.com/22drnn). The patterns of
5,000
16.5
CO concentrations in both tests are almost
16
0
inverses of the O2 levels for this unmodified
0
10
20
30
40
50
60
70
80
90 100
generator. The CO level is low at the beginMinutes
ning of generator startup and increases
CO (Test 1)
CO (Test 13)
O2 (Test 1)
O2 (Test 13)
steadily as the O2 level drops. As the O2 drops
FIGURE 2 Measured CO and O2 concentrations of Tests 1 and 13.
further, causing a very rich fuel mixture in
the engine, CO generation reaches a maximum level. Test 13 shows an extreme case in
zero. The solid points in Figure 3 are data points for a
which the generator eventually produces a zero electrical load after the O2 drops to almost 16%, although it was half-load setting (2.5 kW) and the hollow ones are for
set at a full load and the crankshaft was still rotating.
a full load setting (5.0 kW).
To generalize these test results to other conditions
The second generator was tested in both unmodibeyond these particular tests, it is necessary to confied and modified (low CO emission) configurations.
vert the results into CO emission and O2 consumption Figure 4 presents the CO emission rates as a funcrates. Figure 3 shows 5-minute average CO emission
tion of O2 levels for the unmodified generator, while
Figure 5 presents the CO emission rates as a function
rates as a function of O2 levels in the 13 shed tests
of the first, unmodified generator. For both full and
of O2 levels for the modified generator. Although the
modified generator was not tested as many times
half load settings, CO emission rates increase with
as the unmodified version, these figures show the
decreasing O2, reaching maximum values when O2
drop to about 17% to 18%, and then decline at lower O2 dramatic reduction in CO emission rates due to the
levels. Under the extreme case of Test 13 (5.0kw-CWmodifications included on the prototype. Most of the
LA), the CO rate decreases dramatically as the O2 level modified generator's emission rates were well below
reaches around 16.4% with an electrical output of
500 g/h.

ASHRAE Journal - September 2014

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