Which gas is commonly referred to as the "silent killer" due to its odorless and tasteless properties?

Carbon monoxide is commonly referred to as the "silent killer" because it is a colorless, odorless, and tasteless gas that can be extremely dangerous, leading to poisoning and even death when inhaled in significant quantities. It is produced during the incomplete combustion of fossil fuels like oil, gas, coal, and wood, making it prevalent in both residential and industrial settings.

This property of being undetectable to human senses means that individuals can be exposed to high concentrations of carbon monoxide without realizing it, which significantly increases the risk of accidental poisoning. The importance of proper ventilation and the use of carbon monoxide detectors in homes is emphasized to mitigate this risk.

The other gases listed do not share the same characteristics of being both lethal in a similar manner and undetectable. For instance, carbon dioxide is a normal part of the air we breathe and is detectable, while methane is flammable and can be detected by its odor when mixed with an odorant. Ozone, while harmful in certain contexts, has a distinct smell and is not considered a silent threat in the way carbon monoxide is.