You turn on your iMac — and for the first few seconds everything seems fine

A quiet hum, the desktop, your mail. Then half an hour later it starts sighing like a runner after the tenth kilometre. The fan spins up as if something inside has decided to take off.

Dust is a sneaky thing. It doesn't crack the glass or flood the board. It just settles on the heatsink layer by layer, like snow on a roof eave. And one day the cooling system stops coping: the machine heats up, drops its clock speeds, stutters for no reason. Sometimes it even restarts on its own — not because it's "old", but because it can't breathe under the blanket.

Vacuuming the glass of an iMac from the outside is a bit like sweeping the floor without opening the door to the room. Air can't get through. You need to carefully open it up, remove the display panel and reach the heatsink. The hero in matte armour knows this procedure by heart and does it with jeweller-like care.

So if your iMac is already training for a career as a hairdryer — it's time to stop putting up with it. Count to three: one layer of dust — louder, two — sluggish, three — time to bring it in.