Mechanisms and Quantification of Benzene Emissions from Gas Furnaces and Stoves
While the primary focus of the available studies is on gas stoves rather than gas furnaces, the mechanisms and findings can provide insights into the potential for benzene emissions from gas combustion in general.
What is the Combustion Process that Leads to Benzene Emissions?
Benzene emissions from gas combustion are primarily a result of incomplete combustion. When natural gas or propane is burned, it can produce benzene as a byproduct of partial combustion. This occurs because the combustion process may not fully oxidize all the hydrocarbons present in the fuel.
How Much Benzene is Emitted from Gas Furnaces and Stoves?
Studies have quantified benzene emissions from gas stoves, which can serve as a proxy for understanding potential emissions from gas furnaces. For example, mean benzene emission rates from gas burners on high and from ovens set to 350°F were found to be 2.8 [95% CI: 1.7, 4.6] and 5.8 [95% CI: 3.3, 9.7] μg min–1, respectively. Similar rates were observed for propane burners and ovens. These emissions are significantly higher than those from electric alternatives, indicating that gas combustion is a substantial source of benzene.
How Do Gas Furnaces Contribute to Indoor Benzene Pollution?
Gas stoves and potentially gas furnaces can contribute to indoor benzene pollution. The benzene produced during combustion can migrate throughout homes, sometimes elevating bedroom benzene concentrations above health benchmarks for hours after the stove or furnace is turned off. Factors influencing benzene levels include the type of fuel used (natural gas vs. propane), the efficiency of combustion, and the ventilation rate within the home. Poor ventilation and higher power output can lead to higher indoor benzene concentrations.
How Does Maintenance, Age, and Type of Gas Affect Benzene Emissions?
While specific studies on gas furnaces are limited, it is reasonable to infer that similar factors affecting gas stoves could influence benzene emissions from gas furnaces. These include:
- Combustion Efficiency: Properly tuned furnaces with high combustion efficiency would minimize VOC emissions, including benzene. However, improperly tuned or older furnaces might have lower combustion efficiency, leading to higher benzene emissions.
- Type of Gas: The molecular weight and composition of the fuel can affect benzene production. For instance, propane flames produce more benzene per joule than methane flames.
- Maintenance: Poor maintenance, such as inadequate air/fuel mixing or maintenance issues, can lead to increased emissions of particulate matter and VOCs, including benzene.
Summary
- Gas furnaces, like gas stoves, can emit benzene due to incomplete combustion of the fuel.
- Quantification: While specific data on gas furnaces is limited, studies on gas stoves indicate significant benzene emissions during combustion.
- Indoor Pollution: Benzene from gas combustion can contribute to indoor air pollution, especially in poorly ventilated homes.
- Influencing Factors: Combustion efficiency, type of gas, and maintenance practices are crucial in determining the levels of benzene emissions.
