Effects of HVAC on combustion-gas transport in residential structures

Time-resolved concentrations of oxygen (O₂), carbon dioxide (CO₂) and water vapor (H₂O) produced by controlled propane gas burners are measured at three locations in a residential structure equipped with a heating, ventilation and air-conditioning (HVAC) system. Experiments are conducted to assess the effects of HVAC operating status (off vs. on) and the impact of bedroom door position (open vs. closed) on species concentrations. Change in concentration up to the flame extinction point, the rate of change, and the transport time for the measured species at each location is compared. The CO₂–O₂ concentration ratio derived from these experiments correlates strongly with the stoichiometric combustion ratio. The CO₂–H₂O and O₂–H₂O ratios have a relatively strong correlation though with slightly higher variability. Both the HVAC status and bedroom door position have statistically significant influence on the total change in concentration for all the measured species. However, HVAC status only has a statistically significant effect on the rate of change of H₂O but not CO₂ and O₂ concentrations. For all three species in both bedrooms, the concentrations typically begin to change later in experiments with HVAC off than experiments with HVAC on.