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?