Heh...gotta live homonyms.
I think you meant "threw."
It is dependant on many things...physical health is a big part of it, but not as big as one might think. Level of ACTIVITY is a far more important factor. The 30 kilo guy laying on his death-bed can probably hold his breath longer than the 120 kilo athlete sprinting on a track.
Generally, someone who has not trained can generally only hold their breath less than a minute.
If they took a deep breath before they needed to hold, maybe a minute and change.
Someone whom is trained can hold their breath for up to 4-5 minutes, but this also involves several minutes of "pre-breathing." (For an
extreme example, Free-divers can dive [World Record here] to over 200 metres, and hold their breath for as long as 22 minutes and change!)
Keep in mind, if you are suddenly in a 100% oxygen-less area, you typically have about 15 SECONDS of useable O2 in your bloodstream, then hypoxia sets-in.
If your PCs are in a room that they can't escape within 2 melee rounds, consider the gas wins. If they made the save, they managed to pull enough air to make the escape attempt...or put-on an air mask.
One additional thing to consider...what *is* the gas? After all, no all gasses have to be BREATHED. Simply having it touch you is enough. (i.e.: Mustard gas caused contact burns to the skin of soldiers in the trenches, the gas masks just protected their faces and lungs.) After all, many substances have a transdermal effect. (Ever hear of a "contact high"?
)
For a simple mechanic, I`d suggest 15 seconds plus 1 second per PE attribute point, plus PE bonus in seconds, halved in stress situations, and halved again under high activity conditions.
