Is there a known treshold between diffusion and Bernoulli's flow?

seanflan02

I'm trying to find out if there is a certain known hole size when the principles of diffusion come into place instead of fluid mechanics. I would like to rule out a possible methodology for calculating the hole size of a leaking pressurized vessel. If the hole size is say 100microns, would that be a size that would allow free flow of air through it? Or would it be diffusion?
Does anybody know a treshold?

Thanks in advance