Everest. You just pass out from the low pressure at high altitudes and don’t wake up. Since there doesn’t appear to be scrubbers in that can, how do they filter out toxic gases? They can’t be vented out at those pressures. Just pumping in more O2 creates an Apollo 1 scenario and another level of toxicity. So you suffocate or burn to death when the O2 ignites. I think I’d have taken some cheap fentanyl with me to OD on just in case.
There are scrubbers on Titan.
From one of their video pages: OceanGate Scrubber Overview:
One of the many essential life support systems on a dive is a CO2 (carbon dioxide) scrubber. Our scrubbing system for Cyclops 1 and Titan contains soda lime. Soda lime are white granules that contain a mixture of calcium hydroxide (~75%) and sodium hydroxide (3%) with a precise amount of water moisture and binding agents. They absorb CO2 from the air via an exothermic, water facilitated, base catalyzed chemical reaction. The fans in our subs circulate air throughout the interior so all breathing air is consistently brought to the scrubber unit and cleaned of CO2.