• Welcome to the Fantasy Writing Forums. Register Now to join us!

How much chlorine gas would it take to kill someone in this situation? And how long?

X Equestris

Superhero fiction sort of straddle the lines of fantasy and science fiction and a whole bunch of other genres, but I figured I'd see if anyone here might know.

I'm working on a story involving a puzzle obsessed super villain who has kidnapped a few people and is using what are effectively gas chambers as part of a scheme to shatter the mystique around my heroine. The hostage in question is locked in a ten foot cubed room that's sealed airtight. So my question is the title: how much chlorine would be needed to kill one person in this situation, and how long would it take for said person to die?


Time of death will change depending on how much chlorine gas the villain lets in the room. Under 30ppm, if I'm not mistaken, you get mild to moderate irritation that should clear up with time. At 30, you get more severe pains. Everything goes downhill from there. Around 400ppm of chlorine gas, the person would have half an hour or so. 1000ppm and above, a few minutes is all it would take.

Note that chlorine gas settles most where it's released. If the person wants to live a little longer for a dramatic rescue, they'd move their face as far away from where the gas is coming from (unless there are multiple entry points).

X Equestris

Thanks for the answer. I figured it would probably depend on the amount used, but wasn't sure on amounts.
Last edited:


Queen of Titania
Hello X Equestris.

One of my many dark interests is chemical weapons, and in particular I have read a lot about the widespread use of elemental Chlorine as a weapon during the First World War. I find this element fascinating and beautiful, even though it can do pretty horrible things to people during accidents or attacks.

The first thing that I want to say is that you have a very frightening scenario, judging from the way that you described it. Death from breathing Chlorine (either in a low concentration that kills you later, or a high concentration that kills fast) is one of the worst ways to die that I know about.

Now, about the concentration that would be needed for your story scenario:

Sorry for going Metric here, because I am calculating your 10-foot cubic room as a 3-meter cube. That would be 27 cubic meters, which is equal to 27000 liters. The concentration that would kill fast is indeed 1000 parts per million as Cydare said, and the 1000ppm for that volume of air would be just 27 liters.

That would mean 27 liters of gaseous Chlorine dissolving into the air of that room, so just a tiny amount of liquid Chlorine would be necessary for this. Even concentrations like half of that or less would cause death or at least inflict irreversible pulmonary damage, if the exposure lasts for a considerably long time.

As far as I have read, it's an extremely painful, terrifying and in general a fiendish way to die.