One of the biggest enemies to your PC's performance and perhaps even to the safety or your office/home is accumulated dust. Just a speck of dust in the wrong spot can cause for example a network failure or create a blue screen of death.

In addition to potential overheating dragging down the performance of your PC, creating intermittent PC problems and damaging your PC's components, dust can lead to fires. We've had several of our clients see flames leap right out thru the back of their PC's during normal business hours operation (this is the primary reason why you should turn your computers off when you're not at work or at home unless it has a very specific mission critical reason to be on, for example, nightly back-ups, it is an Internet server, etc.). We have literally seen sparks arise from the dust inside of a PC.

Compressed air typically doesn't do the job because you don't want to just move the dust around or blow it into some other part of your PC: you have to use a vacuum. Compressed air might help to clean out a keyboard but we’ve found it to be of little other use. Plus it has a shelf life, can explode if not stored properly, no doubt pollutes the environment because of the chemicals used to make/store it not to mention the container it comes in, can even create condensation inside your PC if sprayed for too long, and should only be used in areas with adequate ventilation suggesting a health issue. And if not held upright, it can release a flammable liquid that can cause frostbite and creates safety issues for children. So that container of compressed air is in our opinion significantly more risky than the use of your vacuum.

Now if you have some extra bucks and don't trust yourself with a nozzle attachment, then you need to buy a special/small/cannister/shop style vacuum designed for computers that has a lower chance of static discharge and that is the ideal thing to use if available. But most small businesses and home users don't have one of those lying around. The reason why some folks tell you not to use a traditional vacuum is because they assume you are going to accidentally touch the PC with some part of the vacuum or perhaps accidentally ground yourself by holding the PC while you vacuum. The fact is that you could easily zap your computer by walking across a room and touching it. Rather, you just need to be careful and exercise common sense.

Simply attach a nozzle (some like to use the upholstery brush, others even suggest using paint brushes, but a basic non-metallic crevice tool attachment is all that is required) to your vacuum, make sure of course your PC is turned off and fully unplugged and be sure to first touch a non-metallic desk or equivalent grounded object before touching your PC and preferably place the PC as well as stand on an anti-static mat; hover the nozzle directly over and around the power supply, the vents, wires, empty slots on the motherboard and basically everywhere you can and obviously everywhere that you can see dust. Keep the nozzle about 2" away from whatever surface you point it at. For a quick dusting, just do the exterior drives and the openings at the back of your PC to remove accumulated dust in the fan and wherever else there is air flow and around your plugs/slots taking the same precautions. Make sure there are no open slots at the back of your computer; all slots should be properly covered and not left open for dust (and other things) to enter. For a complete job, you obviously have to open the hood.

If compressed air is used around your PC, you still need to use a vacuum while using it so that the dust is removed and moved away from your PC.

Become aware of the amount of air flow coming out of your PC and also become aware of how warm your PC's case typically is (ground yourself before touching it) after being left on for a significant period of time, say a half-day. If no air flow is coming out of your PC, it could indicate that your fan isn't working and your PC could be at risk. Your PC's case should never be hot to the touch. Funny noises made by your PC might be an indication of impending power supply failure, however, as long as air is still sufficiently blowing out the back, a bigger concern might be if you can't hear those noises at all. Keeping your fans and PC generally free of dust will help to keep it as cool as possible.

Computers left on all the time need to be inspected even more frequently as their cooling systems will fail sooner and they will accumulate more dust than other PC's. Insure that your PC's have adequate breathing room and are maintained in spaces that will not contribute to overheating and that paper and other flammable products as well as other electronic equipment are placed at a safe distance from your PC's.