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From: ark@alice.UucP (Andrew Koenig)
Newsgroups: net.sci
Subject: Re: Gas heat
Message-ID: <4920@alice.UUCP>
Date: Fri, 31-Jan-86 22:00:52 EST
Article-I.D.: alice.4920
Posted: Fri Jan 31 22:00:52 1986
Date-Received: Sat, 1-Feb-86 20:06:15 EST
References: <1312@gitpyr.UUCP>
Organization: Bell Labs, Murray Hill
Lines: 18

> In my house we have gas heat, and it seems to dry out the air something
> fierce.  Why is this?  I thought one of the products of the combustion
> of the gas was water, so it shouldn't be necessary to put a pan of water
> on top of the heater so I can wake up in the morning without my eyes
> being dried shut.  My housemates and some friends have made this same
> observation, so I don't think it's co-incidence or my imagination.
> 
> I can think of two possible reasons.  First: by some mysterious mechanism,
> water vapor is removed from the air.  This seems unlikely since I don't
> find condensation anywhere.  Second: the air temperature is raised but the
> amount of vapor in the air stays the same so the relative humidity drops.
> The resulting RH is low enough to dry out the mucous membranes during
> sleep.  Perhaps I just wasn't paying attention, but I didn't notice this
> drying out when I lived in a place with steam heat.

In a normal gas furnace, the combustion by-products go up the chimmney.
If you don't have a humidifier of some kind, you will indeed probably
wind up with very dry air, for the second reason you mentioned.