How hazardous is paint to respiratory health...?

I'm having all my rooms and space in the house painted by workers tomorrow. I have no idea if their using brushes, rollers, or spray. How hazardous is this to my health? I plan on opening all my windows while they paint and staying out all day while someone else keeps watch of the house. The only thing that concerns me is when I go to sleep later on the day, will it affect my health and kill brain cells (neurons)? I'm uming that the paint will be dry by then. I guess you could call me paranoid..I'm afraid that their going to use a spray...