Which gas is known for its reddish-brown color and pungent, acrid odor?

The gas known for its reddish-brown color and pungent, acrid odor is nitrogen dioxide (NO2). This gas is a product of combustion processes and is often associated with vehicle emissions. Nitrogen dioxide can be harmful to human health and the environment, which is why awareness of its characteristics is important, especially in fire-related scenarios.

In contrast, chlorine is a greenish-yellow gas with a strong, irritating odor, hydrogen cyanide is colorless and has a faint bitter almond scent, and ammonia is colorless with a sharp, distinct smell. Understanding the properties of these gases, including their appearance and odor, is crucial for safety and effective response in situations where they may be encountered.