The peak CO concentration ranged from 68 ppm to 125 ppm and the steady state CO concentration ranged from 67 ppm to 109 ppm. 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 catalytic heater was operated in a closed room (ACH ~ 0), the oxygen was depleted from an ambient concentration of 20.9 percent to 8.8 percent. Because the catalytic heater can deplete the O2 concentration to such low levels, the heater poses a serious risk of hypoxia. The degree of hypoxia is further exacerbated by the moderate CO concentration and by an increase in the carbon dioxide concentration that accompanied the depletion of oxygen.
As the oxygen decreased in the chamber, the catalytic heater became less effective at converting the propane and oxygen to carbon dioxide and water vapor. This was reflected by an increase in the hydrocarbon concentration in the chamber, which ranged from 1,050 ppm to 13,440 ppm (5 to 64 percent of the lower explosion limit of propane in air). The unreacted propane further
increases the degree of hypoxia.
The heaters catalyst did not appear to degrade over time. This observation is based on operating two identical heaters on 100 disposable 1-pound bottles of propane (approximately 650 hours).
