OT Don't read this (was Re: Altair MBL source)

[Antonio Carlini]

Paul Koning wrote:

> I'm puzzled by some of the earlier discussion.  In particular,
> the "displace all air" stuff sounds bogus.

I'm sure it is. Even allowing for the fact that halon 1301
(or whichever was the commonly used one) is heavier than air
and will therefore sink, I don't believe that a concentration
of 5% by volume (presumably calculated over the whole room's
volume) is going to become much high enough to displace
enough oxygen to prevent combustion. (Especially since the
sudden inrush of gas plus the presumed pre-existing
combustion will both have caused considerable air currents
and hence mixing).

> From what I remember, the concentration of Halon in the air
> for fire  suppression is only a few percent.  The real puzzle is how
> that can be -- there's lots of oxygen left, yet the fire goes
> out. 

Halon functions by interfering with the actual combustion.
In the presence of combustion (or presumably, just at elevated
temperatures) the halon reacts with oxygen, so at the actual
flame (and nowhere else) the oxygen is consumed and no longer
available to feed the fire.

Antonio


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Antonio Carlini arcarlini at iee.org