Both my Olycat heaters have Oxygen sensor shutoff. I have never had one shut down, even w/ no open venting. These oxy sensor heaters were discontinued because they supposedly will not burn at over 6,000 ft elevation. I have never verified that to be true, because I never camp in hi elevation.
Rich
'01 31' Rexall Vision, Generac 5.5k, 1000 watt Honda, PD 9245 conv, 300 watts Solar, 150 watt inv, 2 Cos 6v batts, ammeters, led voltmeters all over the place, KD/sat, 2 Oly Cat heaters w/ ox, and towing a 2012 Liberty, Lowe bass boat, or a Kawi Mule.