A question on Carbon Monoxide poisoning?

My borhter is building a model car and has used spray paint on it on and off the past week. I have been having a headache lately, and my dad has cold symptoms, and I read that spray paint can cause the poisoning. My brother never opens indows or ventilates when he uses it. No one has breathed it in directly, but could this be carbon monoxide poisoning? How much is needed to cause it?