Or a pocket size one and a thick magic marker if you hate them . . .
Include a ventilator with a fan. Also include a stationary bicycle (which isn’t usually really a bicycle at all, usually having only one wheel) so your , uh , guest can get some exercise. Rig up the stationary bicycle to operate the fan in the ventilator. Then your guest can get himself as much fresh air as he feels he needs, whenever he needs it, along with his exercise too.
Source: Kurt Vonnegut describes such a set-up in Cat’s Cradle.
The obvious objection to a setup in which the guest is responsible for his own well-being is the scenario where the guest has an incentive to end his confinement by any means necessary. Say he’s in possession of secret information, or is a critical pawn in some potential exchange, and he wants to interfere with your plans by removing his value to you. Seems to me the circumstances of the OP call for lodgings which are kept livable for the guest with no action or participation on his part (barring some extreme and unlikely exception).
I just read something about a kidnap victim who died as a result of the kidnappers not realizing that a vent needed a powered fan. They built an underground box, left lots of food and water, had a light, blankets, and even some books and other things for amusement, and a pipe venting to the outside, but it was at the top of this underground box (or very, very small room); there was no vent fan, and the victim suffocated.
IIRC, the body was discovered by cadaver dogs, and the kidnap never solved. It was intended to be a ransom kidnapping, and there was initial contact by the kidnapper(s?), but they dropped everything, and that’s when second, intense search parties went out, with the dogs.
Okay, I’m a little confused. I got an automated reply this morning that my OP was " flagged as inappropriate : the community feels it is offensive, abusive, or a violation of our community guidelines."
But earlier than that was a post saying the post had been ‘restored by staff’ – thank you to whoever.
But the ‘restored’ post came before (as in, earlier in the message list) than the "closed’ message, which also talked about the possibility of a second closure possibly occurring after a reopenging …so, I’m not sure if the post is gone or hidden from everybody except me or what.
Anyway, just to confirm: yes, this is purely a hypothetical situation, I have absolutely no intention of abducting anyone. I was just speculating on the feasibility of holding a hostage safely without the dangers/inconveniences of his captors having to attend to his needs on a on-going basis, daily or more frequently. Maybe that is macabre, but I don’t think it’s wildly out of line with other hypotheticals that have been played with on this forum.
Apparently it triggered some readers, so I apologize for that. To me it was just a curious idea to work out, with no real emotional impact. I can see now that someone could react differently, especially if it evokes something that had occurred to them in the past.
I don’t think you want a windmill or solar panels - someone wandering by might spot them and wonder what they are for.
You are already including batteries for the lantern, so increase those to have enough to run the exhaust fan. I assume your double vent system will be enough (blow out at the bottom vent (per an earlier post CO2 sinks), and let airflow pull in fresh air at the top.
Somebody should be able to size the vents/fan for you, given a single person breathing in there.
For inconspicuousness. A cabin out in the woods might draw the attention of anyone who happens to spot it. Like a hunter or backpacker seeking shelter from a storm or something or someone inclined to see if there’s something worth stealing/vandalizing. The trouble with the various ideas of using a windmill/watermill/solar cell to power a ventilation system is that they would also be eye-catching out in the middle of nowhere, too. I suppose I could fall back on some buried batteries, but I suspect that that might requite an unreasonable volume of batteries. I mean, if you can easily totally discharge a car battery by leaving your head lights on overnight or just sitting there and listening to a baseball game on the radio, surely a fan/ventilator would take more juice?
Yeah, but… When I was ten or so my family was renting a house that also including a storage shed. Decently built, no windows, with a door closed by a padlock on the outside. We used it to hold the lawnmower and various lawn and garden tools. One day I ended up locked inside it. (Yes, I have two older brothers, how did you guess?) After yelling and pounding on the door futilely for a while, I managed to escape rather quickly, using a shovel and one of those claw type diggers to pry lose a board in the roof and destroy the shingles above that. I’ve got to think my hostage might be better at McGyvering an escape than a ten year old, you know?
I’m pretty sure Amazon has that listed as ‘not available’ currently. Just another pandemic caused shortage, I guess.
Evil! I said I didn’t want to harm my hostage, and I think driving them mad falls under that.
Yeah, that would be preferable.
My god, did this happen recently? I hadn’t heard anything about it. I do have a vague memory of someone being held buried in a coffin with some sort of rigged up ventilation system, but the air intake happened to be located close to where some idling car or truck’s exhaust pipe was, and the hostage died of carbon monoxide poisoning. (Though I kind of think that might have been the plot in some cop tv show/movie that I watched, rather than real life.)
There’s this case though the victim survived.
They drove her to a remote pine stand off South Berkeley Lake Road in Gwinnett County near Duluth and buried Mackle in a shallow trench inside a fiberglass-reinforced box. The box was outfitted with an air pump, a battery-powered lamp, water laced with sedatives, and food. Two plastic pipes provided Mackle with outside air.
Also tried in 1976 where a school bus driver and 26 kids were kidnapped and held in a buried box trailer.
A storage shed is not what I would call a solid building. You want a building made out of something like concrete or brick. And don’t leave any shovels or other tools inside when you lock up your hostage.
The rule of thumb is you should stand inside your confinement area after you’ve built and equipped it, take a look around, and ask yourself “How long would it take Andy Dufresne to dig his way out of here?” If your answer is more than ten days, you’re good.
^ You’re not making your kidnap victim do your tax returns, are you? How obtuse. 
Yeah, I think that’s it. I don’t remember what I was reading-- maybe an article on unsolved crimes.
Also, remember that the boss in 9 to 5 escaped because even though they were very thorough, they overlooked a tiny nail file halfway under a drawer.
No, you won’t be trussing someone up that, well, creatively, but it’s still a good touchstone for a real-life situation: the tiniest thing can fall the biggest structure. That’s why the myth of elephants being afraid of mice is so persistent. The idea that a mouse can fall an elephant is very attractive.
Among the multitude of Marc Dutroux’s crimes, were that two of his kidnap victims ended up starving to death.
I forget the exact stats and study, but I want to say that a majority of global kidnap for ransom cases end up with the victim dead shortly after abduction. People pay anyway, it seems.
Horrific crime.
I consider this thread to be in very poor taste, which – from me – is high praise, indeed.
So, in that vein, I offer this possible response to the OP (from a Jewish jokes record that’s almost as old as I am):
Or,
Let me introduce you to the “Chinese Student” kidnapping scam.
- The target is a student in a foreign country, away from family and all things familiar.
- The family has sent the student to a foreign country, away from safety and control.
- The home country has a coercive political party and police force.
- The target knows other students in a similar situation.
The student is contacted by the “Police” from China, telling her that she is in danger, and must go into hiding. She is directed to just go stay with a friend, to not contact anyone, to not user her phone or social media accounts. Her friend is given similar instructions.
Then her family is told that she has been kidnapped, and will be released on payment, and not to contact the police. They are permitted to try to contact their missing child – but she does not respond. She is missing from social media, has not been to classes, and none of her friends know where she is.
The kidnap victim doesn’t even know she’s been kidnapped until she is released …
You beat me to it. The OP’s thread made me think about a Reader’s Digest article from decades ago (or some other source) in which kidnappers had thought all that was needed was a tube for the air to come in, not realizing you need something mechanical to actually move the airflow. I think penultima_thule’s Wikipedia cite was it.
For the CO2 problem, I immediately thought of this scene from Apollo 13:
LiOH + CO2 = Li2CO3 + H2O
I think that “airtight” sort of contraption they made was probably to keep water from going everywhere in the near-weightless part of their flight. So it may be easier in your hostage situation…could you put cans of it around the room and let them do their thing, or would water start to build up on top and prevent CO2 from reacting? Hmm.
Googling, it looks like we exhale about 2.3 lbs of CO2 per day, x 10 days for 23 lbs total. A kg of LiOH can absorb** 920 g of carbon dioxide (i.e. 92% its own weight) so I’m guessing you’d need 23 divided by .92, = 25 lbs of it, assuming it’s pure.
Oxygen could simply be replenished from a tank (medical, scuba, whatever). The CO2 is coming out and not returning as gas. Would the 2 lbs of O2 we breathe each day replace its volume and keep the pressure inside more or less the same? 20 lbs of oxygen, please.
Here’s an interesting read.
There have been some recent cases of fit young people dying in a backyard pool, while trying to hold their breath as long as possible. Perhaps some of them hyperventilated first, and blew off all their carbon dioxide - and along with it, the essential trigger needed for breathing. Then, as they lay on the floor of the pool, without the urge to breathe, they died without taking a single breath.