An idle thought: Reducing life support load

[Kamog]

What would happen if some of the crew are killed in battle, and the balance of Humans to Phong is changed? Now there's too much oxygen or too much carbon dioxide. Then the air would gradually become unbreathable for the race with more survivors. Then if some of the members of the larger race die from the bad air, equilibrium will be restored automatically and the air mixture would go back to normal.

For example:
Many humans die in battle -> less oxygen is used up and less carbon dioxide generated -> percentage of oxygen in air rises, carbon dioxide decreases -> bad for Phong -> Phong die -> ratio of Human / Phong restored.

[Fyron]

Clearly you just have to space a few of the other race to restore balance.

[Randallw]

Yes but the percentage of oxygen is not breathed in by any indiviual, thus that once they run out of their percentage they expire tipping the balance. If there is more CO2 being generated than oxygen, the humans will go along breathing enough until the total amount of oxygen is depeleted at which time the humans will all drop dead enmasse. This all of course avoids the issue that if the atmosphere is an equal amount of CO2 to Oxygen neither species should be able to breathe properly, I think.

[Kamog]

If there is too much oxygen and too little carbon dioxide, you just need to start a nice fire inside the ship to restore balance.

Maybe when you go on a spacewalk, you don't need to carry any tanks of air on your back. You just go in pairs, one human and one phong, and have a tube connecting the two spacesuits.