What is a major hazard associated with chlorine gas?

Chlorine gas is particularly dangerous due to its corrosive nature, especially in damp or humid environments. When chlorine comes into contact with moisture, it can form hydrochloric acid, which is highly corrosive and can damage respiratory tissues, skin, and other materials. This hazard underscores the need for proper handling and containment procedures to prevent accidents or exposure in environments where moisture is present. Recognizing the corrosive properties of chlorine is essential for safety, especially for workers who might handle it directly or be in proximity to it during water treatment processes.

The other options present misconceptions about chlorine gas. It is certainly not non-toxic or harmless; it has significant health risks. Moreover, chlorine gas requires specific precautions during handling, particularly with proper safety gear, to avoid serious health effects.