Substances that restrict or prevent the oxygenation of the blood are called:

Substances that restrict or prevent the oxygenation of the blood are known as asphyxiants. These are gases that can displace oxygen in the air or interfere with the body’s ability to transport or utilize oxygen. Common examples of asphyxiants include carbon monoxide or hydrogen sulfide. When inhaled, asphyxiants can lead to suffocation or significant health risks by reducing the amount of oxygen available to the brain and body, ultimately causing unconsciousness or death if exposure continues.

This understanding of asphyxiants is critical for those involved in hazardous waste operations and emergency response, as recognizing these hazards can inform appropriate safety measures and emergency response tactics. The other options, such as oxidizers, oxygenators, and reactors, relate to different chemical properties and functions that do not specifically address the harmful effects on oxygenation of the blood.