>oldest air on record
Hmm... There doesn't exist any air that's not the oldest air on record. Every breath you take, statistically you are breathing in molecules that were also breathed in by Julius Caesar, or (and please sit down before continuing) Adam and Eve!
>>520554363
Midwit take
Think about where oxygen and carbon atoms actually come from. Some are lighter/heavier than others.
The air organisms exhale depends on what they eat, drink and what air they breath.