Which of the following is NOT a safety hazard in boiler operation?

Excessive noise is not typically classified as a safety hazard in boiler operation in the same way as overheating, low water levels, or odorless gas leaks. While excessive noise can be an indication of issues within the boiler system, such as mechanical failures or inefficiencies, it does not directly pose an immediate risk to safety like the other options do.

Overheating can lead to dangerous pressure and temperature conditions that may result in equipment failure or even explosions. Low water levels can lead to overheating of the boiler components and failure of the boiler itself. Odorless gas leaks, such as from carbon monoxide, can pose serious health risks as they can lead to poisoning without any immediate warning signs. These are significant safety considerations in the operation and maintenance of boilers. Excessive noise, while potentially problematic for mechanical reasons, does not inherently lead to such hazardous situations.