>I thought 65% hydrogen + 30+% oxygen would roughly translate to H2O?
>

Only after creating a spark and igniting the mixture. And a short but effective detonation...

>>
>>I'm not sure where you live, but avoid smoking, or anyone who does - a mix of 65% hydrogen & 30+% oxygen would be extremely explosive. Now if it were 65% nitrogen, you would be much safer (& more likely to be on this planet, which has around 78% nitrogen in the atmosphere & essentially no gaseous hydrogen).