Does the inside of you computer (or even some outside vents on the case) look like this?
Dust buildup in/on your computer will block airflow and trap heat. On fans, dust can make some blades slightly heavier than others, which makes them spin out of balance. This dust buildup imbalance is one of the causes of loud fans.
The dust stuck on top of or between the heat sink blades prevents the warm air from escaping efficiently, keeping those components hot. This dust buildup on components is one of the causes of strange scary beeping and sudden computer shutdowns. The cpu is one of the hottest components in your computer. If it overheats, most cpu’s shut themselves down.
The power supply is also a big heat generator, so keep that clean as well. That is found where you plug the power cord INTO the computer (from the wall outlet).
I personally and professionally use this electric air duster:
Click to buy from Amazon.com
It’s more environmentally friendly than cans of compressed air, more powerful than cans, it comes with different nozzle attachments. If you only have a little bit of dust, just use this to blow it out indoors, and dust your apartment later. If you have as much dust as in the picture, so it’s caked on dust, I recommend you use the duster outside.