Oil based paints. Self explanatory.
oil based
I've used both. Acrylic is basic fume free.
i use oil paints myself and they have a strong odor that can be left on clothes and skin for a while.
Because I have used both types of paints.
Oil has toxins in it and also the solvent needed to clean the brushes and thin the paint
It tends to stink a lot so i usually have a window open when painting with oil paint especially
I've only used acrylic before and have never experienced fumes from it.
Because it is obvious.