nikolapetrov00 :
So how do i remove the danger, example i need to replace and re-solder something. I am planning to buy i new psu anyway but i want to clean this one before i sell it. But i'm asking purely to improve my knowledge because i studied electronics short time ago.
PSU's are not consumer fixable, without a LOT of experience and training.
And this is not something that can be talked through in a forum like this.
If you do this, go to your local hospital emergency room and do it there. That way, at least you'll have a med team right there to maybe get your heart started again.
Just blow air through it, both directions.