How you clean a PSU without voiding it's warranty?

[darael]

Bit of an odd question this, but I want to clean a PSU that is still in warranty. But I normally clean the PSU by lifting the lid off and flicking the dirt off outside.

I'm considering compressed air, but am I right in remembering that caution should be exercised as they can spray moisture in if you're not careful?

 

[Monkeynut]

Compressed air but careful which way you orient the can, or you'll blast flammable propellant inside.