I've been looking for a solution for condensation as well as emergency situations to seal up a bivy during a rainstorm. Using a light 3M respirator and some vinyl tubing I built a "Bivy Breathing Mask." It's quite comfortable although it seems rather bulky to bring on a trip, but it could save bringing along a tarp.



Read more about the "Bivy Breathing Mask" and go here for directions:http://fluidglass.com/outdoor-living/how-to-make-a-bivy-breathing-mask/

This is my first post in the forums, and I'm sure I'll find a lot of interesting advice and projects here in the future.

See you guys around!

- Nessles
http://fluidglass.com

Edited by nessles on 07/28/2012 17:52:02 MDT.

As a HX, mass-flow, psychometric weenie (Chemical Engineering / Berkeley), I have a number of thoughts.

1) absolutely, this will reduce condensation in your bivy,
2) it may take a while to adjust to sleeping with the mask on, but users of CPAP machines (my wife is an MD boarded in, among other fields, sleep medicine) have to deal with much more and they adjust.
3) you definitely took the right approach by using check valves close to one's face. You could share the tubing to reduce weight/bulk, but shared (in = out) tubing inceases the "tidal volume" and while reducing condensation in the bivy just as much, it would increase your uptake of CO2.
4) the reduced CO2 in the bivy may be the biggest benefit. I find I react (unfavorably) to the CO2 when I tuck my head inside my sleeping bag then I do to the humidity build-up.
5) the vinyl tubing you used is cheap and widely available. But HPDE tubing (as used in a radiant slap floor) is tougher and slightly lighter in the same diameter. Readily available in 100- to 300-foot rolls, Home Depot will sell it by the foot. There's 1/2", 5/8" and 3/4" available for residential appilcations and larger sizes for commercial use.
6) the length of tubing is a trade-off. Shorter is obviously lighter and offers less restricted flow. But longer gives you more flexibility in sleeping positions.
7) I strongly recommend you wrap some duct tape around your water bottle so you have some repair supplies handy. Even better is the 2" wide, red plastic tape used to seal vapor barriers in homes - it is stickier, stronger, and lasts for years instead of months.
8) **advanced concept** if you consider a tube-in-tube configuration for greater heat exchange or reduced number of tubes, here's the punchline: for X diameter in the inner tubing, you'll get equivalent pressure drop in a length of 2X diameter for the outer tube. e.g. if 5/8" ID works, you'll need 1-1/4" ID for the outer tubing with 5/8" inside of it. That seems really big with a lot more cross section but it is because of the increased "wetted area" of all those tubing sides exposed to the air flow. Probably better to tape two 5/8" diameters together an forego the HX. Maybe with a stick or lightweight plate taped to the end so it stays outside the bivy
8.1) There are HX masks with two check valves built in sold for aspiring avalanche victims so they can breath in and out of a chest-worn diffuser even when buried in snow. You've achieved something similar at a lower cost and weight, but you might look at those units for inspiration and/or parts. For high-altitude work, I like the how such a rig can capture heat from out-going breath and potentially recapture some moisture as well.

Neat thread, and nice manifestation of the idea John. Thanks for posting.

I have considered making something like this before, this is nicer than what I was putting together in my head...:)

One thing I have used in a similar vein is, dust mask with light fleece pulled over. It took a few tries to find a dust mask comfortable enough for sleeping and I had to punch holes in it b/c I felt like I wasn't getting enough air. The fleece helps hold it in place and acts like a little HTX and captures some of my exhauled moister.

I have wondered if fleece would be more effective directly over my mouth and nose.

interesting project.

I wonder how it'd work for piping exhaled air away from a sleeping bag or balaclava to reduce frost buildup near the breathing hole. Also taking intake air from inside the bag/quilt?

the UL way of course is to use reed tubes found by the rivers ... ninjas use em to hide underwater ;)

of course with that mask you can hide from bears in the river ... or from polar bears under the snow =O

David - Thanks for the insight. The mask will significantly reduce condensation inside the bivy as well as it fits well. I like the idea about inserting one tube inside the other. That would certainly warm the air as it enters the mask while cutting down on bulk - could be a good project for someone to continue on. Good idea on the vapor barrier tape too.

James - Glad you like it!

Jim - Of course you could position the intake tubing inside the bag to pull in heated air and exhale it outside of the bag provided that the input air source doesn't run out!

I'll post it somewhere else, but I use the Marmot Alpinist Bivy and it doesn't have any tabs to hang it from tree branches. Is there an easy way to make a little apex by hanging the fabric ontop so that it doesn't com into contact with the sleeping bag. Perhaps a washer and a line?

- John
http://fluidglass.com

The heat from breath should somehow be trapped in the sleeping system, not just released
to the outside. Same with moisture from breath. Think "DUNE".

For a lighter weight mask you could look into using the masks they use for CPAP machines. They only cover your nose so you have to train yourself to sleep with your mouth closed. I wouldn't think one could, but CPAP users everywhere do. It wasn't hard for my wife and she has slept for "many" years with her mouth open. Basically the have a big band that holds you mouth closed. You wear that for a week or so and you are magically trained.