I can guarantee that >90% of it will float outside the case.
Which usually means that you should take the case to somewhere where said extra dust on air/floor wont harm anyone. Outside is usually pretty good choice.
as example:
you use pressurized air can. (or leaf blower like someone in youtube video's do, I do not recommend this though) and give CPU cooler a short burst.
Said dust in cooler will get blown free and flies outside the case or remains as a dust could.
second short burst past the cloud, on the mainboard, pretty much pushes what remains out of the case.
Rinse and repeat on PSU and GPU and other toys as needed.