How to clean computer hardware safely, inside and out

What you need, and what to leave out

A proper clean needs very little, and most of it is cheap:

Leave household sprays, window cleaner, bleach and solvents in the cupboard, and keep the vacuum cleaner out of the case. The full list, with what each one does to a computer, is further down.

Power down, unplug and discharge static

Cleaning a computer that is only asleep, or still plugged in, is how liquid and screwdrivers meet live circuits. Dell's safety checklist, written for its desktops, laptops and monitors, is a good order to follow for any brand:

1. Shut down fully. In Windows, choose Start > Power > Shut down, not Sleep or Restart. Wait until the lights are off and the fans have stopped.
2. Unplug everything. The power cable at the wall and at the computer, the laptop's AC adapter, and every peripheral: network cable, USB devices, monitor, dock. Take out memory cards and discs.
3. Remove batteries you can remove. That means laptops with a removable pack, and wireless keyboards and mice. Many current laptops have an internal battery; leave it alone unless the service manual shows how to disconnect it.
4. Drain the leftover charge. Press and hold the power button for 15 to 20 seconds.
5. Ground yourself before you touch anything inside. Touch an unpainted metal part of the case, such as the rear I/O panel, for at least five seconds, or wear an anti-static wrist strap clipped to grounded metal. Touch metal again every few minutes, especially after moving around.

Electrostatic discharge (ESD) is the same effect as the snap from a door handle after you cross a carpet. Dell warns that a discharge you never notice can still destroy memory modules, processors and motherboards. Hold components by their edges, never by the gold contacts or pins, keep any part you remove in an anti-static bag, and work over a hard floor rather than carpet. Dell's ideal room has moderate humidity (40 to 60%), and it suggests not wearing fleece or polyester while you work inside a computer.

Which cleaner to use on which part

Isopropyl alcohol is the common ground. Dell's instruction is a microfiber cloth moistened with 70% isopropyl alcohol and 30% water, damp and never dripping. Apple accepts 70% isopropyl alcohol wipes on hard, nonporous surfaces such as the display, keyboard and case. Microsoft allows a solution of 70% or less on Surface devices. Lenovo wipes keyboards with isopropyl alcohol and uses a 50/50 mix of isopropyl alcohol and distilled or deionized water on its displays.

The brands split on ethyl alcohol. Apple accepts 75% ethyl alcohol wipes; Dell and Lenovo both list ethyl alcohol among the chemicals not to use. If you stock one cleaner for a mixed fleet, make it isopropyl alcohol: all four accept it on keyboards, and Dell, Apple and Microsoft name 70% for cases too (Lenovo prefers water or a mild non-ammonia cleaner on its painted covers). Screens are where the makers part ways, which is why they get their own section below.

Inside the case, the rule changes. For removing old thermal paste, HP calls for isopropyl alcohol or a thermal compound cleaner, and warns against standard 70% rubbing alcohol, which it says can cause corrosion and damage internal parts. Use a higher-purity isopropyl alcohol there, sparingly, on a swab. Whatever the strength, isopropyl alcohol is flammable: Lenovo's reminder is never to use it near an open flame or on a system that is switched on.

How to clean a laptop or monitor screen

Screens carry the coatings that are easiest to ruin, and the makers disagree most about them, so start with the gentlest method and stop as soon as the screen is clean:

1. Turn the computer or monitor off and unplug it.
2. Wipe off dust with a dry microfiber cloth. Apple's instructions for its displays start here.
3. For marks, dampen the cloth with water only. Never spray the screen itself: Apple warns that cleaner can drip inside the display and damage it.
4. Wipe gently in one direction, from the top of the screen to the bottom, as Dell recommends, and dry it straight away. Do not press on the panel.
5. Only for fingerprints that water will not shift, use alcohol if your maker allows it: 70% IPA on the cloth for MacBook and iMac displays, 70% or less on Surface touchscreens, a 50/50 mix of IPA and distilled water on Lenovo displays.

There are three exceptions to that routine. Dell's monitor guidance says never to use window cleaners, alcohol, ammonia or abrasive cleaners on its LCD screens, because they can damage the anti-glare coating: water only. Apple's nano-texture glass, an option on some Studio Display, Pro Display XDR, iMac, MacBook Pro and iPad Pro (M4) models, is cleaned only with the polishing cloth that came with it, moistened with 70% IPA for the occasional stubborn smudge. And Microsoft says not to use disinfectant wipes on any Surface touchscreen, even though it allows diluted alcohol on the cloth.

How to clean a keyboard, mouse and touchpad

Keyboards collect crumbs under the keys and skin oil on top, so they need both air and a wipe:

1. Turn the keyboard off or unplug it, and take the batteries out of a wireless one.
2. Blow out the gaps between the keys with canned air, keeping the can upright and using its straw. Lenovo is explicit that this means a can of compressed air, not a workshop air compressor.
3. Wipe the keytops with a lint-free cloth moistened with isopropyl alcohol and squeezed out, so that nothing drips between the keys, then let the keyboard dry.

For a MacBook (2015 and later) or MacBook Pro (2016 and later) with an unresponsive key, or one that feels different from the rest, Apple has a specific routine: hold the laptop at a 75-degree angle, spray the keyboard from left to right with the straw about half an inch (1.3 cm) from the keys, then repeat with the laptop turned onto its right side and again onto its left side. Do not turn the can upside down while spraying.

Fabric keyboards need different treatment. Microsoft cleans the Alcantara on Surface keyboards and covers with a white, lint-free cloth dampened with mild soap and water (five parts water to one part soap). The magnetic connector strip on a Type Cover gets a little isopropyl alcohol on a soft cloth, and Microsoft's advice is to pick any metal particles off the cloth before it touches anything else.

A mouse is a small case: wipe the outside with a cloth lightly moistened with water. If an optical mouse stops tracking smoothly, look at the sensor window under a bright light; Apple's fix for debris there is a gentle puff of compressed air. Touchpads are cleaned like the palm rest around them.

How to clean ports, vents and dust filters

Vents are where cleaning pays off most. Dust settles on the intake vents, fan blades and heat sink fins, exactly the path the cooling air takes, and HP's overheating guide names dust on the fans as the most common reason a computer overheats. HP also says the risk of damage to internal components rises once the temperature inside the case passes 35 °C (95 °F). Dell's maintenance guide tells you to clean the air vents on every side of the computer, and Lenovo's instruction is to clear them with compressed air while the PC is off. Laptops usually breathe through the bottom and the sides, so turn the machine over and work along each grille.

On vacuum cleaners the makers differ. Dell says not to use a vacuum or blower at all, because they create static. HP's own troubleshooting guides use a vacuum on the outside vents of laptops and desktops, and draw the line at the case: never use it inside the computer. The safe reading of both is to keep any vacuum on the outside of a closed case, and to use canned air for everything inside.

Ports need air and light, not tools. Shine a flashlight into USB-C, HDMI and charging ports, blow lint out with a short puff of canned air, and never dig with a pin or a paper clip: Dell warns against putting objects, especially metal ones, into openings that are not meant for them. Keep moisture out of every opening, and do not run a wet wipe across connector pins, which Lenovo also rules out.

Many tower cases have removable mesh dust filters over their intake fans. Intel's cooling guide explains how they work best: with slightly more air pulled in by the intake fans than pushed out by the exhausts (positive pressure), air leaves through the case's small gaps instead of being sucked in through them, so dust collects on the filters, where you can clean it before it enters the PC. That also means the filters clog first. Slide or unclip them out and clear them away from the computer; if a filter is washable and you rinse it, let it dry completely before it goes back. The case manual shows which filters come out and how.

Prevention does as much as cleaning. Give the computer room to breathe: Dell asks for at least 10 cm (4 in) of clearance on every vented side, HP for at least 15.25 cm (6 in) around each vent. Keep laptops off beds, sofas and carpets, which block the intakes, and keep food and drinks away from keyboards, as Dell's laptop care guide advises.

How to clean the inside of a desktop computer

Opening the case is a desktop job. On most laptops, cleaning stops at the vents unless the service manual for your model describes removing the bottom cover, and Dell's advice before any internal work is to read that manual first. All-in-ones and monitors are not for opening. Intel adds one more check before you start: whether opening the case affects the warranty.

1. Complete the power-down and grounding steps above, and give the components time to cool.
2. Remove the side panel as the case manual shows. HP warns that the metal edges inside a case can cut skin.
3. Blow the dust off the fans, the heat sink fins and the graphics card's cooler with canned air, can upright, straw close to the part. Hold each fan's blades still while you blow through it. Intel's cooling guide explains why: fan motors are designed to spin at specific speeds, and forcing a fan to spin too fast, powered or not, can damage the motor.
4. Blow through the power supply's grille, but never open the power supply. HP warns against working on its fan yourself because of the risk of fire and electric shock.
5. Keep liquids off the motherboard and other components, and do not vacuum inside the case.
6. While the case is open, check each fan: nothing stuck in or touching the blades, as HP's fan guide puts it. A fan that does not spin, or makes a loud growling noise, may need replacing. HP's advice is to stop using a computer whose fan is not working correctly, because constant high temperatures damage internal parts.
7. Refit the side panel, and count the screws first: Dell warns that a loose screw left inside can cause a short circuit.

When to replace thermal paste

Thermal paste, or thermal interface material, sits between the processor and its cooler and carries heat across the joint. It is not part of a routine clean. HP notes that paste can dry out and crack over time, which makes the fans work harder; replace it when temperatures stay high after a proper dust clean, or whenever the cooler comes off the processor for another reason.

HP's procedure for its desktops is a good model:

1. Power down, unplug and let the components cool. HP recommends an anti-static wrist strap, a conductive foam pad and a non-carpeted floor.
2. Lay the desktop on its side so the motherboard is flat, and disconnect the processor fan's cable from the motherboard.
3. Undo the cooler's screws in a star pattern (corner to opposite corner) rather than clockwise, so the board is not stressed, and lift the cooler off.
4. Clean the old paste off the processor and the base of the cooler with a swab or microfiber cloth lightly dampened with isopropyl alcohol or thermal compound cleaner, until none is left, including around the edges. Do not take the processor out of its socket; its pins are easily damaged.
5. Put a pea-sized amount of new paste in the centre of the processor.
6. Seat the cooler centred on the processor, then tighten the screws in a star pattern until you feel resistance, and no further. HP warns that over-tightening can damage the socket and crack the motherboard.
7. Reconnect the fan cable, refit the side panel and power on.

On a laptop, re-pasting means taking much of the machine apart. Treat it as a job for the manufacturer's service centre or your IT provider, especially while the laptop is under warranty.

What never to use on computer hardware

Unsuitable cleaners rarely fail on the first wipe. The damage builds up, and the manufacturers document what it looks like:

Two more mistakes involve no product at all. The first is too much liquid: Dell's rule is a cloth that is damp but not dripping, and no moisture visible anywhere before the power goes back on, because moisture that gets inside an electronic product can damage it. The second is cleaning a computer that is still on or plugged in, which Dell, HP, Lenovo, Apple and Microsoft all rule out.

Dry it, reassemble it and test it

1. Let everything air-dry. No moisture should be visible on any surface before the device is plugged in or turned on.
2. If the computer has come in from the cold or from a hot car, wait until any condensation has evaporated before you power it on, as Dell warns.
3. Reinstall removed parts and batteries, account for every screw, and reconnect the cables.
4. Power on. HP notes that fans running loudly for five to twenty seconds at start-up is normal. After that, the computer should be quieter under the same load than before you cleaned it.
5. If a fan still runs loud all the time, open Task Manager and check what is using the processor before blaming dust; it is the first step in HP's fan troubleshooting.

How often to clean a computer

The computer makers avoid fixed intervals. Microsoft says to clean the touchscreen and keyboard frequently, Dell to clean a laptop often, HP to keep the fan vents cleaned regularly, and Lenovo to clean the exterior occasionally. Intel is the one to put a number on the inside: its cooling guide recommends opening the case and cleaning it with compressed air every few months. Beyond that, the rhythm depends on how the computer is used and where it sits. The signs that it is overdue, from HP's overheating guide, arrive slowly, which is why they are easy to miss:

• fans that get louder as they spin faster to shed heat;
• basic tasks taking longer than usual;
• freezes, sudden restarts, or games and applications that stop responding;
• and, before any of those, dust you can see in the vents or on a filter.

Pets, carpets, workshops and building work all shorten the interval. Dell goes further for laptops and advises against using them in dusty environments such as construction sites at all.

A starting point, then adjust to what you find each time. Apart from Intel's "every few months" for the inside of a desktop, these intervals are our suggestion, not a manufacturer rule:

Cleaning computers in an office: a schedule and who does it

In an office the risk is not that nobody cleans the computers. It is that three groups clean them three different ways, with whatever product is in the cupboard. Decide who does what, with which products, and write it down:

A few rules make the schedule work:

• Clean shared devices on a schedule, not when they look dirty. The CDC's workplace cleaning guidance is to clean high-touch surfaces, touchpads and desks among them, regularly. For electronics it adds two points: follow the manufacturer's instructions, and consider wipeable covers.
• One product list for the whole fleet. For a mix of Dell, Apple, Lenovo and Surface machines, that means 70% isopropyl alcohol for keyboards and for Dell, Apple and Surface cases, water or a mild non-ammonia cleaner for Lenovo covers, water for screens, no ethyl alcohol wipes on Dell or Lenovo hardware, and no disinfecting wipes on Surface touchscreens.
• Put cleaning in the asset register. A date against each device shows which machines run hot, which rooms are dusty, and which computers keep coming back.
• Clean and inspect before redeploying. A laptop going to a new starter gets its vents cleared, its fans heard at start-up and its battery checked for swelling.
• Brief the contractors. The product meant for desks and door handles should never be sprayed on a screen or a keyboard.

Our IT support service keeps an asset register of devices and licences and advises on what to replace and when, and a machine that still runs hot after a proper clean belongs on that list. When a replacement arrives, our guide to setting up Windows on a new computer covers the next step.