Which gas is identified by a reddish-brown color?

The gas characterized by a reddish-brown color is nitrogen dioxide, a member of the NOx (nitrogen oxides) family. Nitrogen dioxide is notable not only for its distinctive reddish-brown hue but also for its role as a significant air pollutant, commonly produced from combustion processes such as those in vehicle engines and power plants. Its appearance can indicate the presence of nitrogen oxides in the atmosphere, which can have various environmental and health effects.

In contrast, nitrogen is a colorless and odorless gas under normal conditions, while carbon dioxide is also colorless and has no distinct color. Ozone, despite being a highly reactive gas, is typically described as having a light blue color in concentrated forms, but it appears colorless in smaller quantities. Recognizing the visual characteristics of gases, particularly those that may impact health and safety in environments like mines, is crucial for effective monitoring and response strategies.