First of all, you should switch off the Computer, before you hit him with compressed Air.
Second, it is very unlikely, that a fan is dying because of the accumulated dust on it. Yes, there are Fans dying, and they could be covered with dust, but normally there is no direct relation between this two thinks.
Third, the Fan is just not able to remove the Dust, if you blow it “with compressed air at a reasonable pressure”, because alone the Airspeeds produced by the pressure, and the Airspeed produced by the Fan just don’t work together. The Fan has just no chance, to get the Dust, that has been blown up, into a somewhat controlled Airstream, to remove him. And, if that would be possible anyway, there would no dust accumulation at all.
I had build Computer for Friends, Family and Customer during the last 3 Decades. I haven’t counted them, but it would likely sum up into some three digits.
And I had never one, that died because of Dust on a Fan.
BUT I had a couple of them dying, because of a “clean” Fan, and Dust all over the interior, on the RAM, the CPU, the Cooling Elements, on the circuit board, within connectors and so on.
And I had also a couple of dead Fans, after they where hit by compressed Air, and just overturned, or damaged the bearing by being hit on one side.
If somebody really thing that it is necessary to clean the inner part of an computer, take a Vac, with a small hose (“PC-Hose”) and/or a soft cloth, and wipe the parts you want to clean carefully, while the system is open (and Off, of course!), and remove the dust immediately by the Vac.
I live in a rather dusty environment.
I have my woodshop in the house, a Dog with an almost year-round Coat change, a Dog-Toilet with wood shavings, a lot of trees and flowers around the house, producing a lot of Pollen, and so on.
If I keep the area of my 4 computers and 3 NAS running 24/7 somewhat “clean”, by vacuuming once in a week, I had never a problem with Dust on one of my systems.
So it might be an idea worth considering, to clean the area around the computer once in a while, instead of spreading the dust already inside the computer, with the risk of some damages, caused by this.