Emily,
There have been numerous warnings against canned air on CCD chips. There is some chemical that can cause irreparable damage with one claim I read suggesting you can lodge tiny particles in the between pixels.
Check out this very good site for the latest info.: http://www.bythom.com/cleaning.htm
Take care, Gregory david Stempel FIREFRAMEi m a g i n g www.americanphotojournalist.com
