Mustard gas is the common name given to 1,1-thiobis (2-chloroethane). The name mustard gas was widely used, because it is said to have an odour similar to that of mustard, garlic or horseradish.

Mustard gas is a particularly deadly and debilitating poison. Its real danger when it was first used in the First World War, compared to other chemical warfare agents at the time, was the fact that it could penetrate all protective materials and masks that they had available at the time.

The effects of mustard gas exposure include the reddening and blistering of skin, and, if inhaled, will also cause blistering to the lining of the lungs, causing chronic impairment, or at worst, death. Exposure to high concentrations will attack the corneas of the eyes, eventually rendering the victim blind. Any area of the body which is moist is particularly susceptible to attack by mustard gas, although it is only slightly soluble in water, which makes it difficult to wash off.

If the inhalation of the mustard gas itself does not kill you, it is very likely to cause cancer later in life.