High Pressure gas vents deleting gas

I think I've just seen a high pressure gas vent delete a packet of gas.

I had a vertical column of hydrogen completely sealed off with a gas pump at the top of the column 6 tiles away from the high pressure vent at the bottom.

There was one packet of oxygen at the bottom right over the vent, when I started the pump and the hydrogen started pumping in the oxygen packet just disappeared.

I've attached the save file if that helps, the column that it happened to is just under the chlorine geyser.

Space Hut.sav