More efficient propane furnace

CPSC study wrote:
CO Emissions
When the catalytic heater was operated at the test conditions specified in the standard for infrared
radiant camp heaters (ANSI Z21.63), the steady state CO concentration ranged from 67 ppm to 109 ppm.
Steady state was achieved in approximately 2 to 6 hours, depending on the air exchange rate. Since the
CO concentration in the chamber exceeded 100 ppm during several of the tests, the catalytic heater would
not comply with the CO requirement ANSI Z21.63 (2000). Assuming a limited exposure time of up to
6.5 hours at these CO concentrations, the catalytic heater does not appear to pose a serious CO hazard to
healthy adults when the CO concentration is considered by itself. When the CO emissions from the
catalytic camp heater are compared to those of a typical radiant camp heater, the catalytic heater
generated much less CO (Tucholski, 2002).
Unlike the standard for infrared radiant camp heaters that limits the CO concentration to 100 ppm
throughout the entire test, the current draft of the voluntary standard for portable catalytic camp heaters
(ANSI Z21.62-draft) only limits the CO concentration at two specific O2 concentrations. At an O2
concentration of 19.4 percent, the CO concentration cannot exceed 35 ppm, and at an O2 concentration of
15.1 percent, the CO cannot exceed 250 ppm. When the catalytic heater was tested in a closed room
(ACH ~ 0), the CO concentration in the chamber ranged from 24 ppm to 27 ppm at an O2 concentration of
19.4 percent. During the same tests, the CO concentrations ranged from 101 ppm to 110 ppm at an O2
concentration of 15.1 percent.
Although the catalytic heater would meet the CO emission requirement being proposed in the
new standard for catalytic camp heaters, CPSC staff does not agree with allowing the CO concentration to
reach 250 ppm in a closed room. Sustained exposure to a CO concentration of 250 ppm for 6 to 7 hours
could pose a serious CO hazard to healthy adults. Depending on an exposed individual’s activity level,
this could result in carboxyhemoglobin levels ranging from 24 to 29 percent, where severe headache,
nausea, vomiting and mental confusion could be expected.1
Instead, CPSC staff recommends that the CO
concentration be limited to 100 ppm, the same limit as that specified in the standard for infrared radiant
camp heaters. Camping heaters that meet the CO emissions requirement in ANSI Z21.63 (2000) should
not pose a CO poisoning threat to healthy consumers when the heaters are brought into enclosed spaces.