[tortoise]

Is CO2 toxic and harmful to our health?

[xiankai]

only in concentrations of 5% by volume and above. inhaled air typically consists of less than 1% CO2.

[tortoise]

Can a big amount of CO2 in the atmosphere kill hundreds of people (about 500) ?

[Mitch]

I sniffed dry ice once, bad mistake. It was painful.

[Dude]

No.  Any gas can suffocate if it depresses the oxygen content below 16 %, even nitrogen or argon (non-reactive).  If you want to drop 500 people with CO2, you better put them in a real small poorly ventilated room or use another gas.  

[Donaldson Tan]

you better put them in a real small poorly ventilated room or use another gas.  

CO will be more effective. LOL. CO Poisoning - the leading cause of death in Australia.

[jdurg]

Arrrrghhhhhhhhh.  I wish I could remember the name of the country, but in my general chemistry textbook they mentioned a village where nearly the entire population died as a result of a CO2 expulsion from a nearby lake or volcano.  The CO2 settled into the valley and killed nearly everyone in the village.  Now I'll have to look it up to see where it was.  

[Borek]

Cameroon.

http://perso.wanadoo.fr/mhalb/nyos/disaster/indexdisaster.htm

[Dude]

I remember an article about that.  I think it was in "Smithsonian" or "Natural History" and it was a lake in Africa (one of those countries where finding hundreds of dead bodies is typical-like Congo or Liberia).  The article was written within the last 3 years.  Evidently, CO2 built up in the lake and then released violently (like a Coke bottle top being released).  The mode of death of the villagers was still representative of a suffocating gas (not a poison).

[movies]

Yeah, I remember hearing about that in a lecture too.  It was something like there was a lot of CO₂ in the lowest layers of water in the lake and it was fine until it rained.  Since the rain water was colder than the water near the surface, it caused some of the layers to exchange and as the colder water from near the bottom rose it released a lot of the carbon dioxide all at once.

[tortoise]

I posted this question because I had just read a short story of Pierre Bellemare "Le train fantôme (The Ghost Train) which is translated into Vietnamese.

The story says that 521 persons were killed on the train with a strange reason. And here is the conclude of the investigation committee about the accident: There is a high slope in the tunnel... 2 enginees could not pull the train up, so the train stopped right there. Graphite was burn with a big amount... The quality of graphite was very bad. When burned, it produced a large amount of CO2. This toxic gas quickly spread across the tunnel. Passengers and train crew smelled the toxis gas and died.

In late night of 3 and early morning of 4, March 1994, there are totally 521 victims diesd in the accident. Only 4 were alive because they sitted on the last passenger-car. However, they all were infected with the toxic gas. Their hairs became grey. CO2 affected their brains, which could not be cured.

Maybe this storo tells a real event... I want to ask, does CO2 have that ability?

[Borek]

The story says that 521 persons were killed on the train with a strange reason. And here is the conclude of the investigation committee about the accident: There is a high slope in the tunnel... 2 enginees could not pull the train up, so the train stopped right there. Graphite was burn with a big amount... The quality of graphite was very bad. When burned, it produced a large amount of CO2. This toxic gas quickly spread across the tunnel. Passengers and train crew smelled the toxis gas and died.

Maybe this storo tells a real event... I want to ask, does CO2 have that ability?

I am assuming that by 'graphite' you mean 'coal'.

Burning coal always produces CO₂, regardless of its quality. Low quality coal often contains a lot of sulfur, and the fume has high amount of SO₂.

So the real question for me is: is it possible to kill 521 people in a tunnel burning low quality coal? And the answer is obvious - yes. No problem.

1. Even if the coal is pretty good without ventilation amount of CO₂ produced can suffocate everyone (not to mention partial combustion and CO problem in such a situation, but let's put it aside).

2. SO₂ is much more dangerous and it will probably kill these people much faster then CO₂ buildup.

[movies]

I would guess that in such a case the prime culprit would be CO.  As Borek said, low quality coal won't produce more CO₂ than good quality coal (I would expect much the opposite actually).  There are plenty more nasty components of coal smoke than CO₂!

[tortoise]

oh year, it is CO.. I though it was CO2 !

[Benzene265]

Also, CO₂ isn't mind-altering, but oxygen deprivation can be.  Even if the coal burned cleanly, the O₂ in the train would have been pushed out  by the CO₂ and water vapor made in the combustion reaction.  Also, the burning of the coal itself would have used up much of the free oxygen in the tunnel.  Without breathable air, the passengers would suffocate.  Those who survived could have suffered brain damage from the reduced amount of oxygen in the air.  Incomplete combustion would have been worse since the CO would make the passengers incapbable of absorbing what little oxygen there was.