PH2O being emptied from a bottle emptier onto a packet of CO2 causes violent offgassing of PO2 at the bottle emptier.
I tried to replicate it in a test map for a while, but I couldn't work out the exact conditions, so I just recorded my base where I saw it happen for a while. The video captures the bug.
Bottle empty PH2O onto a CO2 packet. May require airflow tiles or pump around or under.