Which gas is considered the most dangerous emitted from an internal combustion engine?

Carbon monoxide is considered the most dangerous gas emitted from an internal combustion engine due to its highly toxic nature. It is colorless, odorless, and tasteless, making it particularly insidious because individuals may be unaware of its presence until they experience harmful effects. Carbon monoxide binds to hemoglobin in the blood much more effectively than oxygen, which can lead to reduced oxygen delivery to vital organs and tissues. This can result in symptoms ranging from headaches and dizziness to more severe consequences like unconsciousness and even death in high concentrations.

In terms of public health, the danger of carbon monoxide is compounded by its ability to cause significant harm in enclosed spaces, such as garages, where vehicle emissions can accumulate quickly. While other gases emitted from internal combustion engines, like nitrogen dioxide, hydrocarbons, and sulfur dioxide, can also have harmful effects on health and the environment, carbon monoxide is uniquely dangerous in its immediate and severe toxicity to human health.