How does carbon monoxide typically enter the body?

Carbon monoxide typically enters the body through inhalation while breathing. This gas is produced during the incomplete combustion of carbon-containing fuels, and it can be found in vehicle exhaust, smoke from fires, and in the emissions from gas appliances. Once inhaled, carbon monoxide binds to hemoglobin in the red blood cells more efficiently than oxygen, which can lead to reduced oxygen delivery to various parts of the body, causing serious health issues.

The other methods listed—skin absorption, direct injection, and food ingestion—are not common routes for carbon monoxide entry into the body. While some substances can be absorbed through the skin or ingested, carbon monoxide's primary and most dangerous route of exposure is through inhalation, especially in enclosed or poorly ventilated spaces where the gas can accumulate. Understanding this mode of entry is crucial for fire investigation and safety practices.