I'm using Lungplus version that works with something similar to design 1 and have no problem with drowsyness at all. The benefit of breathing warm moisturized a

I'm using Lungplus version that works with something similar to design 1 and have no problem with drowsyness at all. The benefit of breathing warm moisturized air outweighs the very small amount of stale air. I measure it to about 25 ml by filling it with water and shaking it out again. Lungplus is just a silicon wrap around a package of corrugated metal wrapped around itself so the air pathway is straight and very open and easy to breath through. Each pipe is about a millimiter in height and 2-3 in width. It still heats up the air very well at least down to -35 C at which time the freehub starts freezing and I can't bike anyway :-)