Which of the following is NOT considered a visual sign of confined space hazards?

The presence of workers wearing helmets is not considered a visual sign of confined space hazards because it does not specifically indicate any hazardous conditions related to the confined space itself. Helmets are common personal protective equipment (PPE) used in various work environments, including construction and general industry, but they do not inherently signal danger associated with the conditions within a confined space.

In contrast, the other options represent clear signs that could indicate potential hazards. Discoloration of surfaces can suggest chemical leaks or degradation of materials. Presence of condensation may indicate high humidity levels or the potential for water accumulation, both of which can create hazardous environments. Unusual odors often point to the presence of toxic gases or materials that could pose serious health risks. These elements are critical for assessing the safety of a confined space and identifying risks before entry.