For those of us who have computer towers,it,s a good idea to keep it clean inside.
This is especially true if you have dogs or cats.
There are several fans in the case or tower.
One in the power supply(don,t take that metal case apart)another on the motherboard and one stand alone fan.
If possible hold the fan blade from turning while spraying.Use only electronics grade can of air for this.Use short burst of air,2 seconds at,a time.Do not hold the can upside down.
I mentioned earlier about dogs and cats,especially if you have more than one pet.
The fan,s blow air,however to do that they take air in from the room.Which has dust and pet dandruff.This dust builds up on the fan makes it run slow and also coats the motherboard and ram.Acting like insulation.Which makes the computer run hotter.
I normally do this twice a year.