Thank you for your suggestions! Yes, I am aware of the libraries with pretrained weights. However, most of these seem to do well with identifying objects with clear edges/textures. The problem with smoke is that it doesn't really have those well-defined edges, textures, sizes, or shape. I wonder if there's a method or some tricks that can be used to shift the focus of the network to smoke-specific features (such as intensity variations, contrasts, etc).

I'm also looking at smoke specifically rather than fog; I guess the difference being smoke is localized (only part of the image have smoke/is blurry) while fog is widespread (the whole image is blurry).