In terms of human health effects, natural gas is described as an asphyxiant. Which option reflects this?

• A. Non-toxic
• B. Asphyxiant
• C. Humidifying agent
• D. Oxygen supplier

Answer: (B)

The key idea here is how natural gas affects breathing: it acts as an asphyxiant. An asphyxiant is a substance that isn’t toxic in the chemical sense but reduces the amount of breathable oxygen in the environment. When natural gas (primarily methane) leaks into a space, it can mix with the air and push oxygen levels down. With less oxygen available, people can feel dizzy, confused, lose consciousness, or even stop breathing in severe cases. So, even though natural gas isn’t poisoning you directly, it creates a risk by displacing oxygen, which is why the correct label is asphyxiant.

Non-toxic isn’t accurate here because the danger isn’t about chemical poisoning but about suffocation from reduced oxygen. A humidifying agent isn’t a property of natural gas, and an oxygen supplier would imply it adds oxygen, which is the opposite of what happens when gas accumulates.