What's the composition of gun smoke and is it dangerous?
Toxic smoke from propellant combustion has been known about for over 500 years.. 
The propellants used today are Nitrogen based, thus nitro glycerin, nitrocellulose and nitroguanidine . These produce gases containing oxides of nitrogen, carbon oxides, carbon monoxide, hydrogen cyanide, ammonia and several other gases..
The oxides of nitrogen can be inhaled deeply into the lung thus causing damage as deep as the Alveoli, thus causing bronchiolitis obliterins resulting in a "Pulmonary Edema". This can happen 5 years after exposure..
If you show signs within 24 hours of exposure then oxygen and Arterial Blood gas tests are the solution to treating the condition and knowning the effect. The symptons show just like influenza but no sign of virus.
This is known as an Acute Toxic Smoke Inhalation Injury.
WW1 and WW2 this was studied to reduce the effect on gun crews on both land and sea. It is still a problem today with Armoured vehicles and Artillery and one of the reason the Navies use unmanned turrets.
Look up this file and you will find quite a bit of information about this condition.

Occupational Health - The Soldier and the Industrial base

I had first hand experience of this injury in 1988 and am still alive to tell my story, I had a "Pulmonary Edema" in 1991 and survived that, so I am in the 2% of survivors from that period. In the mid 1990's they discovered how to treat a pulmonary edema thus it has increased the survival rate.

There is thousands of pages of information on this subject, just look for "Propellant exhaust gas exposure" or "Toxic gas inhalation" that will bring up more information.

The military threshold limits are higher than civilian but a tank will expose the crew to 1,300 the TLV for less than 5 minutes if the fume extractor is working. In my case it was not!

http://www.public.navy.mil/surfor/documents/p_5041.pdf  Chapter 10

http://www.cs.amedd.army.mil/FileDownloadpublic.aspx?docid=a1d49fb8-3a16-4489-9408-1089f7044b4c

https://permanent.access.gpo.gov/lps101453/www.bordeninstitute.army.mil/published_volumes/occ_health/OHch10.pdf

There are 3 links for you to go to...
Enjoy reading it...
Oh just as an idea, if you had 1,100 .308(7.62mm) rifles fired in a 100 m3 room, its would be the equivalent of 5x L7 105mm tank rounds...
Enjoy..