My townhouse is built on a slab, and the coolant lines for the air conditioner run through a PVC pipe laid in that slab. On the outside end, the pipe is sealed up with a big, goopy mass of silicone caulking which looks like something a curious rodent could get through rather easily.
So, I was thinking to myself, what if I took a bucket, put a piece of dry ice in it, let it … well, not melt, but sublimate or whatever dry ice does. The CO[sub]2[/sub] would be heavier than air, so it would stay in the bucket. Assuming for a certain amount of error, I could, it seems to me pour this heavier-than-air gas into the open inside end of the pipe, effectively filling it with CO[sub]2[/sub] and creating a 20-foot-long tunnel of unbreatheable air for anything inside it.
Am I crazy, or would this kind of work? (I do realize that those aren’t mutually exclusive.)