4 ms·

They're all design 1. Here's a manufacturer link with an air flow diagram for one of the recommended ones: https://www.ergodyne.com/nferno-6970-extreme-balaclav

by dgacmu 3y ago

They're all design 1. Here's a manufacturer link with an air flow diagram for one of the recommended ones: https://www.ergodyne.com/nferno-6970-extreme-balaclava-hot-rox.html https://www.ergodyne.com/nferno-6970-extreme-balaclava-hot-r... That said, the volume of air that could be retained in the foam heat exchange insert is quite small (eyeballing it, maybe 50-100ml?) compared to normal human inhalation volume, about 3-4L per breath during moderate exercise.

londons_explore 3y ago
100 ml / 4 liters = 2.5%. 2.5% of CO2 laden air (~50,000 ppm) + 97.5% fresh air (420 ppm) = 1640ppm. 1640 ppm of CO2 is very much into the 'feels drowsy and hard to concentrate' region.
- _flux 3y ago
  However, per https://www.omnicalculator.com/ecology/co2-breathing-emission#do-humans-breathe-out-carbon-dioxide https://www.omnicalculator.com/ecology/co2-breathing-emissio..., the air a person breaths out has only 4% CO2, reducing that number to 65ppm, right?
  - londons_explore 3y ago
    (40,000 x 0.025) + (420 x 0.975) = 1409.5 ppm
    - _flux 3y ago
      Right you are! I guess the two valves in working masks are then quite essential, and normal breathing masks better have as little extra space for air in them as possible.
- adhesive_wombat 3y ago
  Does that stay true when exercising? At rest, with a tidal volume of 500ml ish, lungs are least 5/6 full of stale air, round down to 3% ish CO2. When exercising, the tidal volumes are far higher (2-3L), and you breathe faster, so the lung air is at least twice as fresh as it was at rest, probably more, since fresh air is functionally 0% CO2, and you're moving maybe 6 times the gas volume in each direction. Does that massive change in volume and diffusion gradient (at least at the start of a breath) means that you might be able to tolerate a higher CO2 level in the inhaled air?
- Moru 3y ago
  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 :-)

by dgacmu 3y ago

londons_explore 3y ago

100 ml / 4 liters = 2.5%. 2.5% of CO2 laden air (~50,000 ppm) + 97.5% fresh air (420 ppm) = 1640ppm. 1640 ppm of CO2 is very much into the 'feels drowsy and hard to concentrate' region.

_flux 3y ago
However, per https://www.omnicalculator.com/ecology/co2-breathing-emission#do-humans-breathe-out-carbon-dioxide https://www.omnicalculator.com/ecology/co2-breathing-emissio..., the air a person breaths out has only 4% CO2, reducing that number to 65ppm, right?
- londons_explore 3y ago
  (40,000 x 0.025) + (420 x 0.975) = 1409.5 ppm
  - _flux 3y ago
    Right you are! I guess the two valves in working masks are then quite essential, and normal breathing masks better have as little extra space for air in them as possible.
adhesive_wombat 3y ago
Does that stay true when exercising? At rest, with a tidal volume of 500ml ish, lungs are least 5/6 full of stale air, round down to 3% ish CO2. When exercising, the tidal volumes are far higher (2-3L), and you breathe faster, so the lung air is at least twice as fresh as it was at rest, probably more, since fresh air is functionally 0% CO2, and you're moving maybe 6 times the gas volume in each direction. Does that massive change in volume and diffusion gradient (at least at the start of a breath) means that you might be able to tolerate a higher CO2 level in the inhaled air?
Moru 3y ago
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 :-)