Forwarded message:

Date: Mon, 26 Jan 1998 19:05:54 +0100 (MET) Subject: Re: Burning papers (fwd) From: nobody@REPLAY.COM (Anonymous)

As usual Jim, your posting is prolific but your science is lacking.

Ad hominims, opinions, and no proof...

bind to whatever it comes in contact with (usually oxygen). The only way cyanide could escape in gaseous form is as HCN, however this cannot happen because the hydrogen has a lower activation energy for combining with oxygen, and thus the reaction is starved of free hydrogen by the time the carbon begins to burn. Various other nitrogen compounds are produced, such as NOx, but this is true of all combustion and not limited to plastic.

I have forwarded to the list a single safety standard for plastics and fires. It *specificaly* mentions HCN, so apparently it not only can happen but does often enough they want to test for it on a national level. There are many more out there and as I said before, if you contact your local fire dept. they can provide you with documentation as well.

A more likely (and deadly) result, which you did not mention, is sulfur dioxide. Most plastics don't contain sulfur, but rubber products may.

Sulfur dioxide is present and does pose a threat, fortunately it's a rather short termed threat and treatable. Sulfur dioxide turns into sulphuric acid in the water of the body. Not to mention it burns up the oxygen in formation. The biggest threat with the acids that are produced in a fire is to your possessions. They soak this stuff up and then when the firemen put the fire out they use water which creates acids. These acids effect the components of your possessions over an extended time.

Sulfur dioxide combines with water to produce H2SO3 and H2SO4 (sulfuric acid) which is quite toxic if inhaled.

Depends on the molarity. It is nowhere near as toxic as cyanide on a per part basis.

Most smoke inhalation deaths result for particles clogging the lungs rather than gases. Cats have a tendency to hide when they feel threatened or injured, an instinct which often imperils them in a burning building.

Actualy most smoke inhalation deaths occur because of lack of oxygen and the elevated temperatures. The actual clogging process would take much longer than the 2-3 minutes most smoke deaths take to occur. As to cats hiding, they tend to hind *under* furniture which is actualy the *safest* place to be, the clearest air is next to the floor. It was also where my cats were found, in the living room under the couch where the smoke very clearly never got below about shoulder height - it stains the walls quite well. The fire didn't even make it into that part of the house, it stopped in the next room. The fire itself burned for less than 20 minutes total because the neighbor saw it about 5 minutes after the person who accidently set it off had left. The fire station was on the next block. It was very quick. The firemen were very careful to explain to me exactly why the cats died, gases from the plastics (HCN was specificaly mentioned) and the temperature of the air (they estimate over 350F). While not enough to cause spontaneous combustion it is more than enough to cook the lungs. The air was hot enough that several plastic bags holding wargame materials within 1 ft of the floor were melted but the paper materials were not even scorched. This would further indicate that the damage was done by the temperature of the gas and not direct flame or smoke.

Also remember that computers have materials in them other than plastic, for example lead and other heavy metals. Batteries and electrolytic capacitors are also sources of many toxic materials.

The leads on most components are an aluminum compound (my background is EE) and they typicaly don't start to burn until well over 800F, aluminum itself burns at 600. Since typical tip temperatures in soldering (lead eutecticts only - not indium composites) are in the 600 to 700 it is clear that pure aluminum would not be desirable. So they mix tin and other compounds with it. As to electrolytics, the liquid plastics that make up the dielectrics are very toxic and most certainly give off xCN compounds when burned. Just for the record, Lead (the element) is not generaly used in modern electronics except in a eutectic solder mix for connections. I have several computers that were burned in the fire and the majority of the solder on the pcb's was *not* evaporated. In most cases it wasn't even melted even though the case was completely gone (2 A1000's that work fine though the cases were completely destroyed by the temperature of the air, not fire).

In short, it's not the plastic that's toxic, it's all the other crap (ink, dye, glue, solder, batteries, dielectric, etc)

Malarky. ____________________________________________________________________ | | | The most powerful passion in life is not love or hate, | | but the desire to edit somebody elses words. | | | | Sign in Ed Barsis' office | | | | _____ The Armadillo Group | | ,::////;::-. Austin, Tx. USA | | /:'///// ``::>/|/ http://www.ssz.com/ | | .', |||| `/( e\ | | -====~~mm-'`-```-mm --'- Jim Choate | | ravage@ssz.com | | 512-451-7087 | |____________________________________________________________________|