Polluted Oxygen spawning from no source [Solved, known issue]

You couldn't attach the save cuz you tried to put it under log files, if you used the box immediately under issue description you can attach any kind of file. The box for posting a reply also allows any kind of files.

Please add some pics too btw.

I had a weird food drop bug... long short, you might have something dirty lodged in a tile. These are unsweepable.

Monitor your o2 overlay and look for a low density po2 spawn location, it's most likely at the bottom of a ladder.

Bottled po2 emits 8.5g every 4 seconds or so. Slime 41.7 every other second... polluted dirt from an outhouse or an outhouse itself will emit po2.

I tend to find its rotting food and it has "Sunk" into an actual tile below it. 

Thank you Plum Gate and BlueLance, I found it, and you're right, it was rotting Meal Lice.  Another instance of it was slime being carried through a really weird path in my base.  So, bug known, wrong concern.  Thanks!