I need an equation for calculating water/oxygen in an airmass

[TedNugget]

I seek an equation to determine the ratio of water molecules / O2 molecules in a mass of air ------- given density, temperature and relative humidity. (Moles H2O / Moles O2)

The volume can be any size, a cubic meter is fine. I’m just interested in the ratio.
Density can be expressed in any measure.

I would prefer temperature in F but C is fine.

Because water displaces other elements in an airmass I believe this could be complicated. Depending on how much Oxygen is displaced or how predictable its displacement is.

I seek to do this over a range of densities that match those from the psychrometric tables for %RH calculation.

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =

Trivia:
I need some accuracy to then see if this has any correlation with wildland fire behavior.
Perhaps paralleling Celsius Crossover (Canadian Extreme Fire Behavior) or Fahrenheit Crossover (Southern US moisture of extinction).

Thanks

 

[Andre]

You may find this tool useful. Just play around, and change settings as you want and it should not be too hard to calculate O2 versus H2O ratio.