What is the term for black smoke that appears whitish near a vent opening?

The term that describes black smoke appearing whitish near a vent opening relates to the phenomenon caused by the presence of particulates and water vapor in the smoke. When black smoke, which is typically associated with incomplete combustion of carbon-based materials, encounters a cooler surrounding air, particularly at vent openings, it can create a visual effect where it appears lighter in color or whitish. This happens due to the condensation of moisture in the smoke as it interacts with the cooler temperature, resulting in a foggy appearance.

In this context, the correct answer encompasses the recognition of this effect as it relates directly to fire behavior and the interpretation of smoke conditions during fire incidents. The other terms do not accurately describe this phenomenon, as they refer to different scenarios or effects unrelated to the appearance of smoke near vent openings.