How do I safely clean the inside of a computer?

Dust is the main reason older computers run hot, throttle and get loud. Cleaning one is straightforward, and the few genuine hazards are all avoidable.

Safety

What you'll need

• Canned compressed air, or a low-pressure blower
• Soft brush and microfibre cloths
• Cross-head screwdriver
• Optional: anti-static wrist strap

Step by step

1. Shut down and disconnect properly.Full shutdown, not sleep. Unplug from the mains, disconnect peripherals, then hold the power button for five seconds to discharge what is left in the capacitors.
2. Discharge yourself before touching anything.Touch bare, unpainted metal on the case. Static you cannot feel is enough to damage components. A wrist strap is better if you have one.
3. Work outside or over a bin.You are relocating dust, not destroying it. Doing it on a desk redistributes it around the room and back into the machine.
4. Never use a domestic vacuum inside.The airflow through a plastic nozzle generates static. Vacuum the dust after it lands on the floor, not off the board.
5. Hold fans still while blowing them.Compressed air spins a fan far beyond its design speed, which can generate current back through the motor and damage it. Hold the blades with a finger.
6. Use short bursts, upright.Canned air tipped over sprays freezing liquid propellant onto components. Keep the can upright and use short bursts from 100mm or so.
7. Concentrate on the heatsinks and filters.That is where the dust matters. The fin stacks on the processor and graphics card, the power supply intake, and any dust filters — which usually pull out and wash.
8. Never open the power supply.It stores a lethal charge long after being unplugged. Blow through its vents from outside and leave the casing alone.
9. Handle boards by their edges.Avoid touching connectors, chips and contacts. If you remove a card, hold it by the bracket and the edges.
10. Do a laptop differently.Blow through the vents from outside, ideally with the machine tilted so dust falls out. Opening a laptop is more involved and may void a warranty — check first.
11. Clean the outside and the peripherals.A barely damp microfibre cloth on the case, and never spray liquid directly onto anything. Keyboards benefit from being turned over and shaken out.
12. Check it boots before closing up.Reconnect and power on with the side off, so a knocked cable is a two-minute fix rather than a full disassembly.
13. Repeat annually, or twice a year with pets.Pet hair and carpet fibre clog a machine far faster. Raising the case off carpet also helps considerably.

Tips

• Hold the fan blades still before you blow them. It is the one step people skip and the one that damages hardware.
• Keep the can upright. Tipped over it sprays liquid propellant, which is cold enough to crack components.
• Raise a desktop off the carpet. Floor-level intakes on carpet are why some machines clog in months.

Common mistakes

• Using a household vacuum cleaner inside the case — Air moving through a plastic nozzle builds static, and a discharge onto a board can destroy components silently.
• Letting fans spin freely under compressed air — They exceed their design speed and can generate a current back through the motor, damaging the fan or what it is connected to.

If it doesn't work