What occurs if the proper combustion air is not supplied to a 150,000 BTU/h rated furnace?

When a furnace does not receive the proper amount of combustion air, it can lead to incomplete combustion of the fuel. This incomplete combustion is hazardous because it can produce carbon monoxide, a colorless, odorless gas that is lethal in high concentrations. Carbon monoxide is a byproduct of burning fossil fuels like natural gas or propane, and when there is insufficient air, the combustion process is disrupted, leading to higher levels of this toxic gas.

In systems designed for specific air-fuel ratios, any deviation can cause safety hazards, not only resulting in the generation of carbon monoxide but also increasing the risk of backdrafting or flue gas spillage, which can also contribute to dangerous conditions. Therefore, ensuring the appropriate amount of combustion air is critical for the safe and efficient operation of a furnace.

The other options reflect outcomes that are either incorrect or misleading in the context of insufficient combustion air. Increased efficiency would not occur; rather, the opposite is true because of the inefficiency caused by improper combustion. While damage to the furnace could potentially occur over time due to improper combustion and heat buildup, the immediate and most consequential impact is the risk of carbon monoxide exposure. No impact at all is simply not accurate, as reduced air supply directly affects the combustion process