Kandy in a premixed, or mixed from concentrate, is no more dangerous than the other urethane base colors, but if he has added a catalyst/hardener to the mix he is spraying, then the hazzards get worse, and a remote air mask is the way to go.

Before you get too paranoid, I've been painting for 40 years, and have not had health problems......... yet....... other than growing an extra arm, and turning pearl green. Just kidding. :-)

You can spray uncatalyzed paints with a charcoal mask, but if you intend to spray catalyzed paint, invest in a remote air setup.