Hi guys! I’m going to write a short story. I’m just wondering, what kind of Doctor who knows something about poisonous gasses like carbon monoxide, mustard gas (during World War 1), etc.
Thank you very much! 
Pretty much everyone near the front line in WW1 - and plenty behind - knew about gasses. Doctors were right up there treating them.
The Doctor. 
Weren’t there some other minor conflicts preWWI that had experimeted with poison gasses? So, a medic in one of those armies?
WAG, sorry
Maybe a pathologist? They ought to know about things that are lethal for humans.
There was at least one episode of Doctor Who that dealt with poison gas.
Two posts above! :mad:
Yes, he does. 
If you want a contemporary physician who would know about the agents typically used in WW1, a medical consultant to an industrial chemical corporation might be one idea.
Heh.
But I’d go with a toxicologist.
There were proposals to use chemical weapons during the Crimean War and the U.S. Civil War, but they were never implemented. I’d be interested to know if there were any instances where “modern” chemical weapons were deployed before 1914.
Maybe not exactly modern, but see Psalm 14. (See also Psalm 53; they appear to be identical or nearly so.)
At least according to this imaginative translation:
(More traditional rendition here. (KJV).)
(ETA: Now, I just gotta look that up in the Lolcat Bible and see how they put it.)