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As a pilot I have a basic understanding of density altitude, how temperature affects the effective air pressure:

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I noticed recently that I have difficulty breathing when I take a shower in Santa Fe, NM, which is at an altitude of 8000 feet. According to the chart above if the shower is 105F / 40C then the effective altitude is actually 12,300 feet due to the hotness of the air. However, this does not take into account the higher humidity of the shower which also has an effect. How can I compute the density altitude inside the shower accounting for humidity as well?

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  • $\begingroup$ As a non-pilot, I must say I had never heard of density altitude before. Makes sense, since who else but pilots would measure density or pressure in terms of how high you would have to fly to experience them? $\endgroup$
    – user10851
    Commented Nov 29, 2015 at 19:45

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To account for the humidity, you need a chart (or equation) that relates the effective altitude to the humidity of the air. For example, if the chart you show here is for 50% humidity, then since the air density increases(lower altitude) as the humidity of the air increases, at 100% humidity, the effective density altitude will be lower. However, if the chart is for 100% humidity, then you already have the correct chart to obtain the effective altitude of your shower!

In conclusion, you need to know the humidity of the given chart, and the variation of air density with humidity, to be able to calculate the effective density altitude.

Regarding your breathing problem, I suspect that it is more likely due to the fact that you are now breathing water vapor in together with the air, thus less oxygen per volume taken in per breath.

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  • $\begingroup$ The chart is for a standard atmosphere. Obviously there is less oxygen. The question is how to compute it. $\endgroup$
    – Ambrose Swasey
    Commented Dec 2, 2015 at 19:14

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