Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: sue howarth on 11/08/2009 14:30:02

Title: If the humidity is high, why don't we drown?
Post by: sue howarth on 11/08/2009 14:30:02: sue howarth asked the Naked Scientists:

Dear Dr. Chris and colleagues,

Several days this week I have noticed the humidity level has been 80% plus and almost every day it is more than 60%. As far as I know, this means the air we breath contains 80% or 60% water. I also know that with too much water in the lungs we drown.

Why then, do we not drown, when we are constantly breathing in so much moisture?

I listen to the programme (http://www.thenakedscientists.com/HTML/podcasts/) on BBC Radio Suffolk, every week-end at 6pm and would really appreciate an answer to the above.

Yours sincerely,

Sue Howarth

What do you think?
Title: If the humidity is high, why don't we drown?
Post by: paul.fr on 11/08/2009 21:59:51: Physiology & Medicine! I can't answer to that aspect, but I think most people have no idea what meteorologists actually mean when they give figures and values of Humidity. Let alone understand the differences in Relative, absolute, specific humidity and dew points.

"Humidity is a measure of the amount of water vapor in the air, not the total amount of vapor and liquid"

This vapor only turns to liquid at 100% humidity. Mist and clouds are a visual representation of 100% humidity. Have you ever watched a distant cloud and noticed the rain falling from it, but that rain did not reach the ground?
Well, thats because the rain went through an area of lower humidity and evaporated.

You may not know the actual amount of water vapour that the air can hold at certain temperatures, at sea level.
30 C: 30 grams per cubic meter of air
20 C: 17 grams per cubic meter of air
10 C: 9 grams per cubic meter of air

Not enough to drown on, I dont think?
Title: If the humidity is high, why don't we drown?
Post by: Variola on 11/08/2009 22:11:02: Briefly, the air we expire is made up of approx 78% Nitrogen, 16%Oxygen, 5% carbon dioxide, and it is saturated with water vapour, the more water vapour we breath in he more we then expel. Thats why on cold wet days, we see our breath coming out in clouds.
We breathe out the vapour that we breath in plus some water molecules produced from biochemical reactions in the body.
Title: If the humidity is high, why don't we drown?
Post by: Chemistry4me on 12/08/2009 05:19:17: Actually oxygen is closer to 21%
Title: If the humidity is high, why don't we drown?
Post by: Variola on 12/08/2009 08:39:50: Quote from: Chemistry4me on 12/08/2009 05:19:17
Actually oxygen is closer to 21%

In expired air????
Title: If the humidity is high, why don't we drown?
Post by: Chemistry4me on 12/08/2009 08:42:59: Oh shite, [:D]

My eyes saw this: Briefly, the air ~~we expire is~~ made up of approx 78% Nitrogen, 16%Oxygen, 5% carbon dioxide

[:I]
Title: If the humidity is high, why don't we drown?
Post by: Variola on 12/08/2009 08:47:03: [;D]

Thats the sort of thing I ususally do! [:D]
Title: If the humidity is high, why don't we drown?
Post by: Chemistry4me on 12/08/2009 08:49:01: Arrg, your Poxyness is coming onto me (What a great pun! if I must say so myself)
Title: If the humidity is high, why don't we drown?
Post by: Variola on 12/08/2009 09:01:14: Quote from: Chemistry4me on 12/08/2009 08:49:01
Arrg, your Poxyness is coming onto me (What a great pun! if I must say so myself)

I dispute that!! I have never 'come onto'you....you are too far away for that... [;)]

I may have rubbed off on you though... [:D]
Title: If the humidity is high, why don't we drown?
Post by: Chemistry4me on 12/08/2009 09:09:24: Oh yeah, cause I just love transpacific/transatlantic (flight number?) rubbing off! Your great Poxy Highness.