No Chill Question

I'd like to build a fermentor from a stainless kettle - that way I know it's large enough and it'll handle boiling wort. However, I'm concerned about the air in the headspace condensing and sucking in outside air. Has anyone solved that problem? I'm thinking just a Co2 adapter and possibly a PSI gauge so I can monitor, but I'd like to hear other suggestions.

Would allowing the negative pressure even be a problem if I plan on pitching as soon as it hits the target temp?

Air IS going to be sucked in. There really is no way around negative pressure. (At least no practical way.)

On the plus side, it really doesn't matter. There is air in there already. As long as you keep it covered, a little extra air isn't a big concern.

+1 don't worry about the little bit of air you will suck in - pitch a large starter so the yeast out competes any wayward bacteria.

I've been no chilling for my last 10 batches or so, I transfer to a regular plastic bucket after the wort has chilled down past 160, I then insert a cork and I can within a few hrs hear the thing sucking air past it.

My last batch I dropped a starter on the floor and only pitched about half of it. Took forever to take off and something terrible(or wonderful) took over instead.

My first infection in over 50 batches and has almost turned me from no-chill a little. However there's so many factors there and we are all due for an Infection at some point.

So yeah pitch a large starter as soon as you can. I'm gonna look into getting one of those cubes people are using that you can sanitize the inside with boiling wort and can handle the pressure as it cools.

I've done no chill for 10 batches in a row now. No issues. I just lay the cap loosely on my fermenter. I have 10 litres of empty airspace in my fermenter and the wort goes in above 190 degrees.

What about one of those air filters used in line with air pumps for oxygenation wort? Maybe you could install one of those into the lid and that way air will get in but hopefully not the airborne particles, bacteria, yeast etc