You have the get most fans to spin at 1800rpm+ to damage them, if you manage to do that with the compressed air can, you'll know about it from just the sound.

There are spray cans of compressed air. and there are electrical air compressors that can be used to fill up tires or balls. This last one can be dangerous if its a powerful one.

The spray cans are usually safer.

spray cans are just as safe as an air compressor if you use the correct settings, it's not that hard really also it depends on how you use the air compressor... sticking the nozzle in the vent and blowing at 100psi is fucking stupid.... if you keep the nozzle at about 6-8 inches away and blow at 25 psi it wont hurt anything. also controlling bursts of air is more efficient than holding the nozzle down with either an air can or air compressor

Yeah uhhh...what are spray cans? :|

Oh I see, sorry we don't use those much in the UK But I'm sure I can find an alternative.

They are easy to get a hold of in cambridge, being from the UK I myself find them at any hardware store, go for the big ones like HomeBase or whatever, and just ask for 'Compressed air'.

I've got to go into town tomorrow, so I'll go check over there then.