We're having our hall, stairs and landing decorated at the moment. The decorator has just sanded seven doors and their frames, skirting boards, countless spindles, banister, etc. Consequently my house looks like someone put a 25kg bag of flour in the hallway, buried a stick of dynamite it, lit the fuse and ran away. A couple of my PCs are internally coated with dust so I could do with cleaning them with some compressed air. Does anyone know where I can buy a large can of compressed air at a reasonable price?