tear gas

Any of various volatile gases that produce irritation and watering of the eyes, used by police against crowds and used in chemical warfare. The gas is delivered in pressurized, liquid-filled canisters or grenades, thrown by hand or launched from a specially adapted rifle. Gases (such as Mace) cause violent coughing and blinding tears, which pass when the victim breathes fresh air, but there are no lasting effects.

Blister gases (such as mustard gas) and nerve gases are more harmful and may cause permanent injury or death.