As anyone who has ever looked inside electronics devices knows, they collect dust and fuzz like nobody's business. Technicians can tell you that first, electronics in use in virtually any environment from the home to the office are constantly exposed to dust (and, in the home environment, pet hair) and that secondly, the electrostatic charge that any electronics device generates attracts dust like a magnet does iron filings. It doesn't matter if the electronics device is a TV, home entertainment system component or computer, if its been in use any length of time, it'll have dust inside.
The first thing a tech will do is use a product like Chemtronics ES1017 Duster to blow out the dust. Believe it or not, clearing the dust out of a system may actually repair a problem as some dust particles can be electrical conductors, making bad circuit connections and causing issues. Also, clearing the dust and debris out of a system with compressed air enables the technician to work in a clean environment which, in the case of computers that haven't seen a lot of maintenance can be very dirty indeed.
In those cases, using a product like Chemtronics ES1024 Typhoon Blast Duster or Chemtronics ES1020 Ultrajet Duster with a heavier compressed air spray can make a huge difference. Dust not only can cake over chips and other components but can work its way under components and boards as well. With the higher pressure, that dust can be blown out where using a normal compressed air spray will require several tries to do it or won't do the job at all. Some dust "infestations" can actually leave a layer of fuzz on a circuit board that can literally be peeled away in a sheet before any duster can be used and in severe cases like these, having a high pressure duster is imperative.
In normal situations, especially when a technician is doing maintenance runs, having an inexpensive duster like Chemtronics ES1217 Economy Duster is the best tool he'll have in his kit. Doing maintenance runs in an office environment is one of those necessary evils that may be boring to do, but saves time and money since keeping computers well-maintained is much easier than trying to repair them later and having a good supply of compressed air makes life a lot easier for a technician as well.
When working on electronics, dust and debris is an unavoidable issue that any technician can tell you is simply part of the job. With compressed air to blow the dust and junk out of the device, not only can the technician get to work on the problem, using compressed air to maintain a system can actually keep problems from happening in the first place.