What specific observation could signal excessive weight loads in a structure?

The observation of smoke from vents can indicate excessive weight loads in a structure due to potential problems such as structural failure or overload, which may cause materials to stress and heat up, leading to smoke generation. In a situation where a building is experiencing more weight than it was designed to handle, components like beams and support structures may begin to fail, potentially leading to overheating or combustion of materials. Therefore, the presence of smoke serves as a critical warning sign of underlying structural issues that could be exacerbated by excess load conditions.

In contrast, the other options do not directly relate to weight loads. The color of paint on rafters, the type of flooring finishes, or the amount of furniture present in the building do not provide reliable indicators of structural stress or weight distribution. These elements may reflect aesthetic choices rather than structural integrity or capacity, making them less relevant when assessing for excessive weight loads.