On 05Jul2020 1037, Vareck Bostrom wrote:
> Traveller (at least T5) is very much open to interpretation in terms
> of the meaning of the different kinds of Atmospheres. "Thin"
> supposedly inflicts "Suff-1" though I had always thought that within
> Traveller Thin, Standard and Dense were breathable without support by
> Humans. At the same time, a sea-level Standard atmosphere becomes a
> Thin one at 1000 meters altitude where the pressure is still ~89.8
> kPa, and becomes VThin at 8000 meters (35.7 kPa for Suff-2).
> Realistically Suff-1 and Suff-2 should be applied based on the O2
> partial pressure or perhaps the ratio of O2 partial pressure to total
> pressure.
>
> Consider a world with a surface pressure of 200 kPa and an O2 partial
> pressure of 4 kPa. The O2 partial pressure would be equivalent to a
> "Trace" atmosphere on the T5 altitude table but the overall pressure
> is either Dense or Very Dense. On the other hand, what about a world
> with a surface pressure of 32 kPa but 100% O2? That would be VThin and
> suffer Suff-2 yet this is equivalent to the atmosphere inside most
> real-world space suits. (also, density is less than 0.5 kg/m^3 and
> many insects will be unable to fly at 1g. Great for selecting worlds
> to vacation on when you don't want to deal with mosquitos).

In CT Book 3 'no' and 'trace' means you need a vacc suit. 'Very thin'
means you need some kind of compressor or supplemental oxygen. 'Thin',
'standard', and 'dense' require no assistance, unless 'tainted' in which
case you need a mask. 'Exotic' (type A) require oxygen, but not suits.
'Corrosive' require protective suits or vacc suits. 'Insidious' as
corrosive, but it eats suits in 2-12 hours. There were more extensive
rules for exotic, corrosive, and insidious atmospheres in JTAS 17.

MegaTraveller gives pressures along with types (I'm not sure if this is
new to MT).

0    Vacuum    0.00
1    Vacuum (Trace)    0.001    0.09
2    Vacuum (Very Thin, Tainted)    0.10    0.42
3    Vacuum (Very Thin)    0.10    0.42
4    Thin (Tainted)    0.43    0.70
5    Thin    0.43    0.70
6    Standard    0.71    1.49
7    Standard (Tainted)    0.71    1.49
8    Dense    1.50    2.49
9    Dense (Tainted)    1.50    2.49

TNE repeats this table.

--
Rupert Boleyn <xxxxxx@gmail.com>