If you must blow dust out of anything take it outside and use proper caution! I used to work as an office repair tech and as a welding supply center tech and blowing things out is great and effective if done properly.
Being outdoors is one requirement and proper eye and possible breathing protection is recommended as well.
Also be careful as to what you blow air into or on to you may actually force dust into something that is not ever supposed to have it there. Like the breather holes on hard rives or the optics on a CD/DVD drive.
And dont rev up the cooling fans with the air hose! 40K RPM'S sounds wicked but those little fan blades go through clothing and skin like tissue paper when they come loose!