Yes, we really are selling cans of air! The CA-4000 professional grade air duster from Nexus is extremely powerful and has been designed to remove any build-up of dust inside a PC chassis. Just watch as it instantly transforms your PC components back to their original form - you'd think they were new again! USAGE INSTRUCTIONS: Ensure target components are fully powered off before using. Hold can upright when spraying and do not tilt can more then 40 from the horizontal during the spraying operation. Use in short bursts only and do not shake the can. The expelled air can be very cold so avoid contact with skin. Do not spray at people or animals and if the can becomes very cold during use, leave it at room temperature for around 15-30 minutes before continuing. If cold expelled air causes condensation on target objects, ensure that the moisture is fully evaporated before powering electrical components back on. We recommend that air dusting is carried out in an open space (preferably outside) so that the blown dust is safely blown away from the immediate working area.