To maintain a proper temperature inside the chassis, PCs have fans. They draw cool air into the room and expel hot air. On a stationary PC, the ventilation grilles are placed at the back. A tower on the floor sucks in a lot of dust. And it's even worse if you have furry pets. Not to mention the cigarette smoke that settles everywhere, including on the air grills and fan blades. Also, regularly clear your machine of dust that can accumulate on the vents or clump on the components. To do this, use a compressed-air canister . You can also clean your computer manually with a small brush that you can gently wipe over the dirty parts: simple and effective, especially if you open your computer;
Whether it's a desktop PC or a laptop, your computer needs air. So you should never block the air vents. For a fixed PC, be sure not to place it too close to the wall. For a laptop, check the location of the vents on the chassis. They can be placed underneath, on the sides or at the back of the case. Make sure that they are always free and that you do not place the computer on a blanket, a plaid or any other soft surface that could block the fresh air supply. Similarly, if the air intake is located under the chassis, don't hesitate to raise the computer to improve the flow of fresh air.
If nothing is blocking your computer's air vents and the fans are constantly spinning at a furious pace while no power-hungry applications are running, you may be a victim of cryptojacking. Hackers have infected your machine with a virus. The computing power of your PC is made available to them to generate virtual currency. A tool like Malwarebytes (free for 14 days) should detect such intruders.