Excessive dust can limit the performance of the intake-fan and heatsinks. If the fan can't blow enough air or the heatsinks are covered with dust then the heatsinks may get warmer. And if your PSU's controller is smart enough then it can limit the output power due to the increased temperature read from the sensor (s) attached to the heatsink (s).
if it's just dust then use canned air. A compressed air can't damage the PSU, you can even lay the PSU fan down on the table and give it a few good whacks so the dust would unclog from it's heatsinks and other stuff properly. Just immobilize the fan before you dust the PSU, sticking a pencil or smth in the fan grille will do.
Dust buildup is a common issue that can affect the performance and lifespan of various computer components, including the power supply unit (PSU). Over time, dust particles can accumulate inside the PSU, obstructing airflow and causing overheating. This can lead to system instability, increased noise levels, and even hardware failure.
Maintaining a clean power supply unit (PSU) is essential for the optimal performance and longevity of your computer system. Dust buildup can obstruct airflow, lead to overheating, increase noise levels, and even cause hardware failure.
Now we are ready to clean the power supply unit. As we mentioned earlier, if your PSU does not have much dust, you can clean it without tearing it apart. You should get a probe or stick and insert it in between the fan blade. This will prevent the fan from rotating while cleaning.
One special advantage of facing it downward is that dust cannot enter the PSU that easy, although it's possible to put a 140mm dust filter (SilverStone for example) on top of it (yes yes, it impedes air flow a bit, but as long as temps stay okay, that's not a real issue and you know, dust doesn't do any good for temps either).