When should I replace foil with an air lock

[Home_alone1]

So i didn’t do my homework and ended up without the required materials to make blow off tubes on my Hefeweizen. I brewed it 2 days ago and it has been spewing out from under the foil into my fermentation chamber. Not a big deal as it’s contained and it’s fermenting well. I’d like to add an airlock after the Krausen dies down a little bit want to reduce the chance of infection . How , when or should I put an airlock on without knocking some of the dried yeast back into the beer without possibly infecting it . Should I even be worrying about this?

 

[ESBrewer]

There is probably nothing to worry about. Just put the airlock on before the fermentation stops. If you wait too long the air may become a problem.

 

[wilserbrewer]

Once the foam drops and is below the top outlet of the fermenter, likely 2-3 days.

Simply put, shortly after it stops barfing out the top lol.