How long would the air last...

Did the guy eat beans for dinner? Might make a difference to the calculations.

A scuba tank at 3000psi holds about 80 cubic feet and about an hour of dive air.
Your room is 36,000 cubic feet so my guesstimate is two to three weeks.

It depends. The CO2 you exhale is heavier and you may get covered in a blanket of the stuff, before the oxygen content of the place runs out because it is in the top of the room...

Kentuk said:

A scuba tank at 3000psi holds about 80 cubic feet and about an hour of dive air.
Your room is 36,000 cubic feet so my guesstimate is two to three weeks.

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That offhand looks like a good calculation, but I would be worried about the eventual buildup of CO2 as well as the depletion of oxygen, which doesn't happen to the air coming out of a compressed air tank. I might round down that guesstimate to one week.

Is this a truly sealed room? If it's an 'ordinary' room in an ordinary house ore office building, I suspect enough fresh air would pass through vents, cracks and such to keep someone alive for longer, perhaps even indefinitely, even without any of the air blowers running.

Assuming the room is airtight, what you're dealing with is percentages. I'm not positive about these numbers and I'm too lazy to look it all up.

I believe normal air is 21% oxygen. Somewhere around 15%, the oxygen content is too low to maintain human life. You'll see some comments on this regarding the mine disaster in Utah, where they were reporting the O2 levels that were being discovered in the mine.

As you person breathes in air, he would be taking oxygen and replacing it with carbon dioxide. By the way, this would not be 21% oxygen in and 21% carbon dioxide out. I'm not sure what the numbers are. This would be calculated as a percentage of the volume of air breathed in and out. Average volume of air moved per breath is 500 cm3.

Lots of math here. I'm thinking I'd contact a college that teaches mining engineering and talking with them. They're probably the experts in this area.

Best of luck,

Jim Clark-Dawe

There was a case a couple of years ago of Chinese immigrants being brought into Britain in a lorry, on a ferry. While on the ferry, the driver closed the air vents of the back of the lorry, and when the lorry was opened at the other end, only one person of about 50 was still alive. I don't remember if the driver knew the people were there or not.
This was a ferry trip of several hours - it was maybe airtight for around 12 hours or so.
One or two people in the same space would have survived with no problem.

Kentuk said:

A scuba tank at 3000psi holds about 80 cubic feet and about an hour of dive air.
Your room is 36,000 cubic feet so my guesstimate is two to three weeks.

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But you're not accounting for the CO[SUB]2[/SUB] emitted...

lfraser said:

Thanks. The room is airtight. I just wanted to make sure that my character could realistically stay alive for a day or two in there. Obviously she can.

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Oh yeah, she should... any time longer than that, there are all kinds of complications: CO[SUB]2[/SUB], human waste, etc.