Been racking my brain the last while thinking about "survival situations" all possible scenarios, how to plan for each etc. and I ran into a couple of probable snafu's that I couldn't really think of an answer to ....... hoping that some of the people on here with a bit more knowledge on such matters might be able to help. - My family and I have retreated into our underground concrete shelter / bunker .... how do I go about concealing any / all noise produced within as I don't want to compromise our location to the scavenging hordes that are roaming around topside. - Shelter will also require a couple of pipes or tubes that will need to protrude out of the ground for ventilation, this also poses a concern because of drawing undue attention to shelters location and also the sound factor as pipes will transport noise to the surface. I suppose you could conceal pipes by scattering debris around ................... also wouldn't escaping carbon dioxide be visible in cold temperatures ? - I'm also thinking of an adequate heat source while in a shelter. I know that the use of small heaters/ stoves fuelled by naptha or kerosene in small areas give off fumes ........... Something solar powered maybe?
The pipes could be concealed with a pile of large rocks or 'junk', noise could be a problem from a elect vent fan, I have both and a very quiet hand-cranked fan for ventilation. Also I can seal the whole system and recycle the air though a scrubber. Heat is not a problem with my 'pit', once 3 or 4 adult bodies are there the temp rises significantly. I have a battery bank in there for power recharged from my off-grid house system.
With something built into the ground, you've already got the natural temperature mediating effect of the surrounding earth. All you have to worry about is, possibly, raising it to a "comfortable" level, and perhaps heat loss through access ways. Like BB said, once there are warm breathing bodies inside, keeping it COOL will be the hard part. I've thought of having the vent stacks in a hedge row. It would allow air through, be flexible, provide natural baffling of sound, to a limited degree, and also temperature dampening, again in degrees, depending on the dimensions and density of the chosen hedge. Downside of that is it takes a couple of years to get it growing. Placing these both next to something that already makes noise naturally further helps camouflage noise. Let's say that this installation is under a somewhat tucked away space in a working farm. What's to say that there isn't, for the purposes of the working farm, a wind mill pulling a dug well for crop irrigation, or cattle. The wind mill will make a certain amount of noise. And, in winter time, water being drawn up from below ground would steam a bit when it hits open air. It was "accidentally" left running when the balloon went up. What's more innocent than that. Oh, and the hedges around the perimiter of it just keep those nosy cattle out of the dangerous works. You'd only have to worry if some REALLY observant person was right on top of you. And if somebody in the waste has got access to thermal imaging equipment sophisticated enough to detect the change in CO2 content from a waste air stack, well, your hiding place may be the least of your worries. We're just talking about keeping the Yahoos off the door.
