What does a placard showing a man wearing a gas mask indicate?

A placard showing a man wearing a gas mask indicates the presence of materials that require a breathing apparatus. This symbol is meant to alert personnel to potential airborne hazards, such as toxic gases or vapors that may pose a risk to health. The visual of the gas mask suggests that the substances in the vicinity could be harmful if inhaled, necessitating the use of proper respiratory protection to ensure safety while handling or being near the materials in question. Such precautions are crucial in environments where hazardous materials are stored or transported, emphasizing the importance of using the appropriate protective equipment to mitigate health risks.