What is a common indoor source of carbon monoxide (CO)?

The correct answer reflects that vehicle exhaust is a well-known source of carbon monoxide, particularly when vehicles are operated in enclosed spaces like garages. When gasoline or other fossil fuels are burned in an engine, CO is produced as a byproduct. If a vehicle is running in a confined area, the concentration of CO can quickly rise to dangerous levels.

However, while vehicle exhaust is a significant source in specific contexts, it is essential to recognize that indoor air quality can be affected by many other sources as well. For instance, natural gas leaks, cooking appliances, and wood-burning stoves can all contribute to indoor carbon monoxide levels. Cooking appliances may produce CO if they are gas-powered, and wood-burning stoves can emit CO if used improperly or when wood is not burned efficiently. Natural gas leaks can also release CO as a result of incomplete combustion.

Overall, in the context of indoor sources of CO, cooking appliances and wood-burning stoves are particularly significant alongside vehicle exhaust, but those primarily affect indoor environments through direct use or when improperly maintained. Therefore, while vehicle exhaust is an important source, focusing on common indoor sources includes consideration of gas appliances and stoves as well.