[SML] Smoke vs Heat vs Rate of Rise detectors

[mouse at fieldmousepro.com]

George Davidson wrote:

> One note we were always given is that the mist systems displace the 
> oxygen, so get the hell out if it goes off.

I think whoever said that was conflating water mist systems with 
something else. Yes, Carbon Dioxide extinguishers (and many other gases, 
for that matter) will displace oxygen. Yes, Halon and it's newer flavors 
will bind to oxygen and render it useless. Fires, of course, will 
consume oxygen.

But water mist displacing oxygen? Not buying it. I can't remember 
getting light-headed the last time I walked through a fog bank or a rain 
shower. If fog displaced oxygen, then most of San Francisco would be an 
uninhabitable wasteland. ;)

However, I have seen several movies where bad creatures would emerge 
from the fog.

As an interesting aside, some very benign things will also consume 
oxygen, rust being one of them. The mention of ships reminded me of 
this: There have been more than a few sailors who have died from 
asphyxiation when they climbed down into the chain locker (a large 
storage compartment in a ship which holds the anchor chain when it's not 
deployed). The air inside the compartment turned out to have very little 
oxygen because the rusting process on the chain had slowly consumed it. 
It was a cautionary tale to never enter a confined space without 
ventilating it thoroughly first.

> 
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