Is it safe to clean inside of cpu for dust with this brush https://www.colourbox.com/image/fluffy-brush-to-clean-the-dust-im

ohhhhh hellllllllll no kid! do not use that it will more than likely cause some static and harm ur pc parts, might as well brush the inside of your pc off with carpet. if you go on amazon they sell antistatic brushes and little football looking things that you squeeze to blow air out and it is reusable i havent had much experience with the football duster but i hear it works very well and is practical for clearing out the tight spots. they also have different sizes which all vary in price too [strike]or you can just buy a can of canned air[/strike] either one of those will work just dont use a feather duster or any like that one in the pic. Good luck (sorry for being so blunt).

antistatic brush on amazon
http://www.amazon.com/uxcell-Plastic-Handle-Circuit-Brushes/dp/B00BM38YPW/ref=sr_1_4?ie=UTF8&qid=1450774315&sr=8-4&keywords=antistatic+brush

football thingy
http://www.amazon.com/Giottos-Rocket-Blaster-Blower-Large/dp/B00017LSPI/ref=sr_1_7?ie=UTF8&qid=1450774356&sr=8-7&keywords=air+duster
 
Well, if you want to go to next best (non-compressed air) alternative... (I wont recommend it but it would work) some vacuum cleaners allow you to use it as a blower instead. said blown air isn't static and will be strong enough to put most compressed air cans to shame.
Of course, that all hinges on the fact if person owns a vacuum cleaner with that feature.

If not, buying new vacuum cleaner for that feature would be silly, you would get a truckload of compressed air cans at same price.