# Could a molecular cloud be breathable?

Molecular clouds in deep space are fascinating objects. Various organic molecules have been found there (including alcohol, heh heh).

So if one of these clouds contained about 20% of oxygen, would it be possible to breathe it in the inner regions of the cloud?

• The percent oxygen is not the important number for respiration, instead what matters is the partial pressure of oxygen which needs to be around 0.2 atm. – Lex Oct 27 '17 at 18:02

Not a chance.

Those "clouds" are a vacuum, but just a vacuum that has a few more particles than outside those "clouds". The density of those "clouds" around 1–100 particles per cm³. You can't breathe it at all.

You may want to look at this Scaling in Density page at Princeton University:

Earth: 5.5 gram/cm³, $1.8 \cdot 10^{23}$ molecules per cm³,

Earth atmosphere: 0.0012 g/cm³ (Wikipedia),

Molecular Clouds: $2 \cdot 10^{-22}$ gram/cm³, 10 molecules per cm³.