Recently my mind has turned to the problem of excessive humidity – not because I’m suffering from it currently, but because I was curious as to how an algae-based CO2 scrubber could be used without having to live in a near 100% humidity environment! This was, apparently, one of the issues with the algae biocoil in the Biosub project. In the end, I blew through a tube and got dizzy – here’s why.
My first thought was to investigate how dehumidifiers work – and at their simplest they’re just using the same process as the condensation on the side of a cold drink. A fan blows humid, warm air over some cooled metal surfaces – the condensation drips off the heat-sinks into a reservoir and the less humid air goes out the other end. Some of them reheat the air on exit.
My next thought went to Dune, and the stillsuits that feature so strongly. I wondered if, using a peltier heating/cooling panel, one could condense the moisture out of exhalation, and collect the condensate in a reservoir for later drinking. I didn’t have a peltier panel for testing (though it seems that Sparkfun does a 4cm by 4cm one) but I do have ice cubes. I got a conical flask and a length of aquarium air-pump tubing and coiled the tube inside the flask, both ends poking out the top. Then I filled it with ice and water, and started blowing.
After going light-headed a few times (the tube is too narrow for human breathing) I did manage to get a teaspoon or two of breath condensate. I promptly drank it. Some of you might be thinking “Eww!” but it had no taste and was pleasantly cool from going through the ice condenser. I promptly declared myself ‘from Dune’ and took some proper deep breaths to stop feeling so lightheaded ;)
So I can say, the image above from the film Dune, is very silly – there’s no way that tiny narrow tube to the nose could carry away the breath of a human in a short enough time (unless there was a pump at the other end, sucking, I suppose, hrm…). If I were to improve my ‘stillsuit mask’, I’d externalize the condenser, I’d include either twice as many tubes as I had before (or use a fatter tube) to make it easier to breathe, I’d use a Peltier panel instead of ice, and I’d attach a proper reservoir, instead of just holding a little plastic cup next to the tube ;)