Saturday, March 17, 2007

CHLORINE GAS ATTACK: Sickens 350, bad guys trying harder

"Gas attack sickens 350" reads an AP story on a mixed explosive-chlorine assault in Iraq today.

Two attacks, one in which "[a] suicide bomber detonated a dump truck containing a 200-gallon chlorine tank rigged with explosives at 7:13 p.m., also south of Fallujah in the Albu Issa tribal region, the military said. U.S. forces responded to the attack and found about 250 local civilians, including seven children, suffering from symptoms related to chlorine exposure, according to the statement."

The other, "... a similar explosion involving a dump truck south of Fallujah in Amiriyah that killed two policemen and left as many as 100 local citizens showing signs of chlorine exposure, with symptoms ranging from minor skin and lung irritations to vomiting, the military said."

Fortunately, although its psychological value may be worth something, the bad guys are finding chlorine is difficult to use as an immediately fatal poison gas.

Your friendly neighborhood GlobalSecurity.Org Senior Fellow can show why this is with some rough calculations, stemming from background as a Ph.D. chemist and as one who worked with substantial amounts of liquid saturated chlorine in cylinders in water sanitation at a large community swimming pool.

Let's assume best case scenario for the bad guys, worst case for people at the initial strike point.

Given one two-hundred gallon cylinder [see editor's note], assume it is full -- and I'll make the statement here that it's probably much less -- and contains liquid chlorine.

Liquid chlorine has a density of about 1.5 g per milliliter.

Let's also do fast calculations because that's what informed emergency responders would want or have to be doing on the spot. (The possibility for error exists here although I'm fairly sure this is accurate to the order of magnitude which, practically speaking, is all that's important for a comparison with other real world instances of poison gas warfare.)

There are about 3785 (or 4000) milliliters in a gallon.

If the release is one hundred percent efficient from an absolute volume of 200 gallons, you would derive 1,200,000 g of chlorine. That comes out to about 2,640 lbs or a little over one and a quarter ton.

By contrast, in the first chlorine attack in gas warfare on the western front in World War I, the Germans -- from a historical account -- released 160 tons of chlorine, not by explosion, but by opening a vast array of cylinders.

The bad guys are limited in their ability to get sufficient quantity of the gas into the immediate environment quickly and in great concentration. Compared to the traditional gas attack, they're deficient by two orders of magnitude. This is a significant barrier for them.

It also tends to explain why relatively immediate fatalities are few. Also consider, use of explosion to release this amount of chlorine has its pros and cons. It does it fast but there's no reason to believe it is particularly efficient in getting the most material on target, which is the aim, one supposes.

Earlier discussion on chlorine attack is here.

And for the slightly more procedurally-minded, there is discussion of chlorine release scenarios at a standard municipal water treatment facility here. Worst case scenario, readers will note, involves the release of one ton of the element.

Additional things to ponder: Chlorine attacks on this scale are uninteresting and insignificant from a military standpoint. In WWI, gas was employed in high volume in hopes that it would crack trench fortifications. Historically, it wasn't particularly successful in this endeavor. Nothing was on the western front.

In Iraq, it's obvious employment is as a terror weapon. But one must wonder at the savvy and long view of those employing it. Chlorine used in this way only serves to harden civilians against the employers of it. It must be seen as even more indiscriminate and pointlessly cruel than the standard daily bombings.

Armchair Generalist furnishes some more dissection.

Editor's note: An alert reader responded that in the old version of this write-up, DD made a mistake in stating "given one 200 pound cylinder..." A 200 gallon cylinder, containing chlorine of the stated density, would have weighed considerably more.

Quite right.

In my haste to publish, the fingers and brain slipped. But not on the final calculation which corrected the error, stating an optimal amount of chlorine at over one ton.

Thanks and a tip o' the hat.


Blogger J. said...

THANK YOU for providing a more analytical point of view on the chlorine attacks. I just tend to say "what's wrong with you people, comparing the chlorine gas incidents to Halabaj?" I should walk them through the math, as you've done.

6:15 AM  

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