Does someone get a headache painting with oil?

I have even ditched mineral spirits. I’d like to know if it’s something else, or pure oil also is harmful to breathe.

Also, what do you recommend to improve ventilation? I paint near the window but it’s not a good ventilation at all since it’s the only window in the room. I have air purifiers but I suspect they don’t work with oil.

Say I buy a fan, will it help? Or it will just move air around?