American Home Inspectors Training (AHIT) Practice Test

What is the least desirable product resulting from incomplete combustion?

1. Carbon dioxide

2. Water vapor

3. Carbon monoxide

4. Oxygen

The correct answer is: Carbon monoxide

Carbon monoxide is the least desirable product of incomplete combustion because it is a colorless, odorless gas that is highly toxic to humans and animals. When combustion occurs in a poorly ventilated space or when there is insufficient oxygen, carbon monoxide is produced as a byproduct. It can bind to hemoglobin in the blood much more effectively than oxygen, leading to reduced oxygen transport in the body, which can result in serious health issues and even death. In contrast, carbon dioxide and water vapor are normal byproducts of complete combustion, with carbon dioxide being less harmful at moderate levels. Oxygen is not a product of combustion; instead, it is a reactant that is consumed during the combustion process. Thus, among the options listed, carbon monoxide poses the greatest health risk and represents a significant environmental and safety concern, making it the least desirable outcome of incomplete combustion.