I recently switched from canned air to a rechargeable electric duster because I was tired of constantly buying cans. During my first cleaning, I kept the PC powered off and held the fans still, but the airflow still felt very strong around the GPU heatsink and the small motherboard connectors. Nothing seemed damaged, but I'm unsure what the actual risks are: static electricity, spinning the fans too fast, or simply forcing dust farther into ports and crevices. For people who clean their computers regularly, what's a sensible routine and working distance?
3 Answers
The safest routine is to shut the computer down, unplug it, move it somewhere ventilated, and blow dust outward rather than deeper into the case. Hold the duster a few inches away, work in brief passes, and angle the airflow so dust exits through the open side or vents. Don’t scrape the nozzle across the motherboard, and avoid using a household vacuum directly on the components because of static risk.
A strong blast from very close range can knock loose cables, damage a fragile fan blade, or push dust into places you can’t reach, but normal airflow won’t suddenly destroy a motherboard. Pay extra attention around loose connectors and small fans, and use a lower setting if the duster has one.
You generally don’t need to worry about the airflow itself damaging components. Keep the nozzle from touching the board, use short bursts, and don’t hold it right against delicate connectors or heatsinks. Electric dusters made for electronics are usually fine when used with a little common sense.

The fans are the main thing to watch. Letting them spin wildly can generate a small voltage, so holding the blades still or stopping them with a finger or plastic stick is a reasonable precaution.