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Date:         Mon, 8 Nov 2010 14:37:17 -0800
Reply-To:     Alistair Bell <albell@SHAW.CA>
Sender:       Vanagon Mailing List <>
From:         Alistair Bell <albell@SHAW.CA>
Subject:      moisture from breathing
Comments: To: Mike S <>
In-Reply-To:  <>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

Assumptions: 160lb human, breathing in/out 6l air/minute (reflects slower resp rate when sleeping) ambient temp -5 deg C (Canadian winter camping eh?) 70% rel humidity

At this humidity there'd be 2.4 mg h2o/l of air inspired. Exhaled air would be heated to body temp / 100% humidity

Heat up for 49.3 mg h2o / l "Humidity deficit" = 49.3 mg h2o/l MINUS 2.4 mg h2o/l = 46.9 mg h2o/L

At 6 L air /minute there would be 281.4 mg h2o / min expired.

This works out to 135 ml h2o over 8 hours.

obviously less than your result for daytime rate, but your guess was pretty good. But might be more for mouth breathers (what's that you say BenT?)


On 8-Nov-10, at 2:25 PM, Mike S wrote:

At 05:00 PM 11/8/2010, Alistair Bell wrote... > Michael, you'll love this, I have the data on how much water vapour a > sleeping 160lb guy breathes out when asleep in - 5 C van.

Please do tell. A quick google says humans lose 350-600 ml/day of water due to respiration. It would be lower during inactivity (sleep), so I'm guessing in the 75-100 ml range for 6 hours. But if it's -5C in the van, maybe it's more because you're shivering without a heater.

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