Doing some research and need a little information

[hunterjwizzard]

Hi folks,

I'm doing some research for a novel and am hoping to get some information. I'm working on a scene in which a character dives down under a lake and surfaces inside a stone building. The "air pocket" is above the level of the surface of the lake but the structure is air-tight. In this case the structure while artificially is essentially a cave, a very thick-walled stone building now buried beneath an artificial mound.

I have read from various sources that in a scenario like this, the air inside the pocket should not be breathable, but I am trying to get a better idea of why and precisely what realistic measures my protagonist needs to take to not die. At present I have the character free-diving in, then putting on a gas mask, but somehow I don't think that's right. I'm hoping someone here can give me a better sense of this.

Thank you in advance!

 

[boulderjohn]

I am not a scientist, but I don't know why the air in the room would not be breathable. It would eventually not be breathable because of the loss of oxygen, but it will be breathable longer than another airtight room because it would not be filled with carbon dioxide as quickly. The water will absorb a lot of the exhaled carbon dioxide. A few years ago there was a case of a man surviving in an air pocket in a capsized ship for longer than people would have thought possible because of this.

I assume the gas mask idea is to prevent inhalation of something toxic, but I have no idea what that would be.

 

[lexvil]

It’s a novel not a science paper.

 

[boulderjohn]

I have always fancied myself almost a writer, and I have a lot of "draft" stories that I can't even get my family to read, which I take as a clue to their marketability. When I watch TV shows, I am constantly reminded of one of my problems--I am far too concerned with realism. I drive my wife crazy every time I point out something that is ridiculously unreal in a show. I can't allow myself do that in my writing, so I am trapped by the need to have everything make sense.

The worst are the police dramas.

• Did you ever notice that in every single episode of every TV police show ever made, as soon as the police see someone in the far distance that they want to capture or at least talk to, they feel compelled to shout that person's name out from that distance so that their quarry has time to get a good, running head start and we can waste 5 minutes of the show with a prolonged chase scene?
• Did you ever notice that when the bad guy has a hostage and is holding his gun to the hostage's head, and he threatens to shoot the hostage unless the police officer puts his or her gun down, the police officer always obliges? I am pretty sure that if a real police officer did that, the gunman, no longer needing to hold the gun to the hostage's head, would then shoot the police officer. A real police officer might realize that if the bad guy were to shoot the hostage, he would no longer have a hostage to protect him.

So, maybe the best thing to do is not worry about reality and just figure the audience won't care.

 

[boulderjohn]

It’s a novel not a science paper.

As I implied in post #4, the problem is that mistakes like this are called "plot holes," and English teachers (like me) scoff at them. But lots of very famous stories have them, and the writer gets away with it. S. J. Perelman wrote a series of hilarious articles showing some of the absurdities of famous works. For example, in the first book of the hugely popular Tarzan stories, a man raised by the apes finds a chest full of books in the jungle. Never having seen a book, he intuits what they must be. He uses the books to teach himself to read, write, and speak English, with a perfect Oxford accent.

One of the most popular stories of all times is "The Most Dangerous Game," in which a famous hunter becomes the hunted prey. I once wrote an English lesson that illustrated all the ludicrous plot holes in the story.

But then, these are all famous stories, and I haven't published a thing.

 

[hunterjwizzard]

Thank you all for the initial replies, much appreciated.

I'm not attempting to take a huge stand on realism, but I do like to check these things out. If you dig a little you'll find the internet littered with forum posts that begin with "I'm doing some research for a novel and...", and only about half of them will be from me (No joke: I've been on skydiving forums, rock climbing forums, if its in one of my novels, I probably talked to people like you about it).

The reason I come and make posts like this is enthusiasts like you all can give me much more helpful insights than can be gleaned from hours of reading technical documents on the subject.


Now back to my initial problem. I had read a real-life account from some years back about a man scuba diving in a flooded mine, who died inside an air pocket. I've heard of similar things happening in flooded caves. Its also been said that when Egyptian tombs were first breached the air inside was toxic. Again, difficult to get insights into all this without talking to people who've done it.


On the flip side, if you're telling me its reasonable that an airtight room, sealed off from the outside world for thousands of years but connected to a water source, should still contain perfectly breathable air, then I can just write the scene that way and run with it.

 

[hunterjwizzard]

A few years ago there was a case of a man surviving in an air pocket in a capsized ship for longer than people would have thought possible because of this.

I am well familiar with that story, did you know the guy is a rescue diver now? So cool.

 

[boulderjohn]

On the flip side, if you're telling me its reasonable that an airtight room, sealed off from the outside world for thousands of years but connected to a water source, should still contain perfectly breathable air, then I can just write the scene that way and run with it.

I saw a few brief moments of a Laura Croft movie in which a scooter into a fully submerged ruin with a breathable air pocket thousands of years old, and there is not only enough air for her and everyone else who shows up, the rooms are even flooded with daylight. If she can do it, so can you!

Why does the room have to be airtight?

 

[lowwall]

Hi folks,

I'm doing some research for a novel and am hoping to get some information. I'm working on a scene in which a character dives down under a lake and surfaces inside a stone building. The "air pocket" is above the level of the surface of the lake but the structure is air-tight. In this case the structure while artificially is essentially a cave, a very thick-walled stone building now buried beneath an artificial mound.

I have read from various sources that in a scenario like this, the air inside the pocket should not be breathable, but I am trying to get a better idea of why and precisely what realistic measures my protagonist needs to take to not die. At present I have the character free-diving in, then putting on a gas mask, but somehow I don't think that's right. I'm hoping someone here can give me a better sense of this.

Thank you in advance!

As you described, it would be life sustaining and remain so for quite a long time until the character's exhaled CO2 built up enough to cause problems.

Note I said "life sustaining" rather than "breathable". You can breathe all kinds of gas mixtures that will feel just fine until you die from it.

If you wanted to make it non-life sustaining, build it from iron. Rust is caused by the binding of O2 molecules from the air with iron. Eventually enough oxygen will be removed to make it deadly. This is a real problem in ship maintenance and especially ship scrapping. Lots of people have been killed entering sealed empty spaces.

I guess you could achieve the same effect in a stone building with anaerobic bacteria and decomposition of detritus. You'd want to note the presence of lots of disgusting slime and foul odors. This article might be helpful The Western Australian Speleological Group - Foul Air in limestone caves and its effects on Cavers

 

[hunterjwizzard]

I saw a few brief moments of a Laura Croft movie in which a scooter into a fully submerged ruin with a breathable air pocket thousands of years old, and there is not only enough air for her and everyone else who shows up, the rooms are even flooded with daylight. If she can do it, so can you!

I saw that movie too and thought that scene was incredibly bad. Got absolutely eviscerated by critics. Don't get me wrong, I love Tomb Raider; but things like that stretch my willing suspension of disbelief past the breaking point.

Why does the room have to be airtight?

Well since you asked...

It doesn't "have to be" for any narrative reason but rather is due the circumstances that created it. I don't normally delve into these details when I have these discussions, but I see we've got an aspiring writer and an English teacher who might be vaguely interested.

The air pocket exists inside a temple. Originally the interior was accessed by descending down into a deep pit and then climbing stairs up into the structure. In the thousands of years since it was built, the pit flooded and the temple was built-over by newer construction. So what was a stone building on the surface is now buried under 5-10 feet of fill with other buildings sitting on top of it. I suppose it might not be 100% airtight, but there's no ventilation shafts or other mediums creating an exchange with the outside air.