Choking agents are not a common chemical weapon, not nearly as deadly as nerve agents but have the advantage of being very easy to manufacture.

History:

Chemical irritants were first used by the French during the first world war, deploying Xylyl Bromide as a tear gas against Germany.

The German military then researched the used of chemical weapons and launched the first chlorine gas attack on the allies on the 22nd of April 1915. Later the first phosgene attack was carried out the 19th of December 1915.

Following these attacks, both the allies and Germany used chemical weapons, manufacturing a total of approximately 100,000 tons of chlorine and 40,000 tons of phosgene put together.

Typical agents:

  • Chlorine
    Formula: Cl2
    Description: Yellowish-green gas, extremely strong smell. Symptoms from inhalation usually occour 30 minutes after exposure.

  • Phosgene (CG)
    Synonyms: Chloroformyl Chloride, Carbon Oxychloride, Carbonyl Dichloride, Carbonic Dichloride
    Formula: COCl2
    Description: Clear gas, odour is weak since smell is impaired by exposure. Boils at 8oC, hence typically used as a gas. Effects felt after approximately 4 hours, full effect within 12 to 24 hours.

  • Diphosgene (DP)
    Synonyms: Trichloromethyl Chloroformate
    Formula: C2Cl4O2
    Description: Very similar to phosgene, although typically a liquid (boils at 127oC).

  • Chloropicrin (PS)
    Synonyms: Nitrochloroform, Trichloronitromethane, Nitrotrichloromethane
    Formula: CNO2Cl3
    Description: Oily colourless or light-green liquid with a very strong odour, possible explosion hazard.

Effects:

Choking agents all have similar effects, attacking the lung tissue through inhaltion, they usually lead to a pulmonary edema (build up of liquid in the lungs), symptoms of which include:

  • Chest tightness
  • Coughing
  • Shortness of breath
  • Hypoxia
  • Choking
These agents all cause irritation to the eyes (diphosgene less so), and the symptoms usually manifest themselves 4 hours or so after the initial exposure.

Manufacture:

Chlorine is very easy to obtain, read Amoeba Protozoa's writeup on chlorine for more information.
Phosgene can be obtained by reacting carbon monoxide and chlorine with a catalyst.
The simple equipment and techniques needed to manufacture these chemicals makes them dangerously accessible to anybody with basic safety precautions.

Treatment:

Symptoms may take up to 12 hours to appear, so regular re-assesment is needed.
Those exposed should remove contact lenses and should seek rest and warmth, since exercise may worsen effect of a pulmonary oedema.
Choking agents damage lung tissue, since normal oxygen absorption will be impaired, oxygen should be administered.
Sedation will help with coughing, but (of course) should only be administered by a trained physician.

In the long term, lung damage will result in breathing difficulties (shortness of breath, tightness in the chest), and possible bacterial infection.

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