Which of the following is classified as an asphyxiant toxic gas?

• A. Ammonia (NH3)
• B. Ozone (O3)
• C. Carbon monoxide (CO)
• D. Sulfur dioxide (SO2)

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the definition of an asphyxiant toxic gas. An asphyxiant is a substance that can cause unconsciousness or death by suffocation, typically by preventing the body from getting enough oxygen.
2. Step 2: Review the properties of each gas listed: Ammonia (NH3) is a pungent gas that irritates the respiratory system; Ozone (O3) is a strong oxidant and respiratory irritant; Sulfur dioxide (SO2) is a toxic gas that irritates the respiratory tract.
3. Step 3: Recognize that Carbon monoxide (CO) is a colorless, odorless gas that binds strongly to hemoglobin in the blood, preventing oxygen transport and causing oxygen deprivation in tissues.
4. Step 4: Conclude that because Carbon monoxide (CO) interferes directly with oxygen delivery in the body, it is classified as an asphyxiant toxic gas, unlike the other gases which primarily act as irritants or oxidants.
5. Step 5: Summarize that the key characteristic of an asphyxiant toxic gas is its ability to reduce oxygen availability to the body, which is the defining property of Carbon monoxide (CO) among the options given.